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Article

Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics

by
Xi Wang
1,2,
Guohui Ma
1,3,*,
Naijie Feng
1,2,*,
Dianfeng Zheng
1,2,
Hang Zhou
1,2,
Jiahuang Li
1,2,
Jiashuang Wu
1,2,
Bing Xu
1,
Weiling Su
1 and
Yixi Huang
1
1
College of Coastal Agriculture Sciences, Guangdong Ocean University, Zhanjiang 524088, China
2
South China Center of National Saline-Tolerant Rice Technology Innovation, Zhanjiang 524088, China
3
National Salt-Alkali-Resistant Rice Technology Innovation Center, Sanya 572000, China
*
Authors to whom correspondence should be addressed.
Agronomy 2025, 15(2), 309; https://doi.org/10.3390/agronomy15020309
Submission received: 18 December 2024 / Revised: 22 January 2025 / Accepted: 24 January 2025 / Published: 26 January 2025
(This article belongs to the Section Plant-Crop Biology and Biochemistry)
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Versions Notes

Abstract

:
Salt stress exerts a notable influence on rice’s normal growth and development process. It causes a decline in rice yield, and in certain extreme cases can lead to the complete failure of rice crops. Abscisic acid, also known as S-ABA, may play an important role in regulating rice plant responses to various stressors and promoting crop growth against adversity. In this research, the impact of externally applied S-ABA (0.03% S-ABA, diluted 100 times) on the growth and yield of rice was explored. The experiment made use of the traditional rice variety Huanghuazhan as the test material. The study focused on how S-ABA affected rice at various growth phases under salt-stress conditions. The effects of S-ABA sprayed once (three-leaf/one-heart stage) and twice (three-leaf/one-heart stage, break stage) on the photosynthetic characteristics, antioxidant metabolism, membrane lipid peroxidation products, osmotic regulation, and yield of rice under 0.4% NaCl were studied. The experimental outcomes indicated that the presence of salt stress had a restraining effect on the growth of rice. There was a notable decline in the net photosynthetic rate; moreover, the yield was diminished by 26.90%. Salt-induced stress clearly imposed negative impacts on these aspects of rice’s physiological functions and productivity. The exogenous application of S-ABA was highly effective in mitigating the inhibitory influence of salt stress on the growth of rice. When S-ABA was sprayed on two occasions, there was a notable increase in the total chlorophyll content within the rice leaves, ranging from 7.40% to 80.99%. This led to an enhancement in the photosynthetic ability of the plants. Additionally, the growth of rice seedlings was significantly promoted. The activity of antioxidant enzymes also witnessed an upward trend, and the content of soluble protein increased by 0.87–2.60%. The content of malondialdehyde and hydrogen peroxide were decreased by 4.18–12.49% and 13.71–52.18%, respectively, the damage to membrane lipid peroxidation was alleviated, and rice yield was increased by 14.84% and 29.29% after spraying S-ABA once or twice under salt stress, respectively. In conclusion, salt stress inhibits the growth and development of rice during grouting and destroys the antioxidant system of the rice plant, thus reducing its yield. Leaf spraying with S-ABA can alleviate the degradation of chlorophyll, enhance the photosynthesis, antioxidant system, and osmotic regulation ability of rice, reduce salt-stress damage, and thus alleviate the yield loss under salt stress to a certain extent. In addition, the regulation effect of two sprayings of S-ABA is better than that of one spraying. The results of this study revealed the physiological regulation mechanism of S-ABA at different growth stages of rice under salt stress, and provided theoretical support for the reduction of salt-stress damage to rice. This suggests that S-ABA has potential applications in the improvement of salt tolerance in rice.

1. Introduction

Rice functions as a main food source for more than half of the world’s population, contributing around 50% of the daily caloric needs for human beings [1]. It is recognized that rice belongs to the category of crops highly sensitive to salt [2], and salt stress imposes severe limitations on its growth and development. Soil salinization in coastal areas is caused by unsuitable crop management, over-exploitation of groundwater, and seawater inpouring [3,4]. The stress induced by salt is capable of considerably diminishing the yield of rice. Moreover, it can bring about various symptoms. Salt stress disrupts the normal physiological functions within the rice plant, which not only causes a decline in its productivity but also gives rise to visible signs of abnormal conditions such as leaf chlorosis, premature aging [5], and delayed flowering and panicle formation [6], affecting tillering, the spikelet number, and the grain weight [7]. It can also cause oxidative damage, ion toxicity, and osmotic stress to plants. In particular, salt stress leads to decreased soil permeability potential, reduced water absorption, partial closure of the stomata, and weakening of photosynthesis intensity, thus inhibiting plant growth and development [8]. Furthermore, when plants are exposed to salt stress, the level of reactive oxygen species in plant cells increases significantly. Salt stress disrupts the plant’s physiological balance, causing a substantial rise in reactive oxygen species. This can trigger events affecting the plant’s normal functions and health. This dramatic increase causes membrane lipid peroxidation, inflicting damage upon the cell membrane system [9]. Due to soil salinization and the ever-increasing world population, rice production will not be able to meet population demands. Therefore, the availability of saline land for rice growing and the exploration of rice production under salt stress are critical to China’s food security.
Rice may face salt stress in all growth stages. However, it is especially sensitive during the three-leaf stage. Salt stress can affect rice at any phase, but the three-leaf stage is when the negative impacts are most evident, and the plant is more vulnerable to high salt levels [10,11]. Therefore, augmenting the salt tolerance of rice in the seedling stage holds substantial importance. It is crucial for guaranteeing the normal growth and development progression of rice. Moreover, it contributes to the enhancement of rice yield in the following growth periods. By improving the ability of rice seedlings to endure salt stress, we can establish a solid foundation for the healthy growth of rice plants, which in turn positively impacts the overall productivity of rice in later stages of its growth cycle. Moreover, the breakage stage is another critical period for ensuring rice yield. At this stage, rice enters the tasseling period from the pregnant spike stage; when 30–50% of the spikes are able to extend 1 cm, rice enters the breakage stage. This period is an important turning point in the growth and development of rice, and proper management can significantly improve rice yield. Numerous prior studies have demonstrated that the application of external substances can effectively enhance the salt tolerance capabilities of crops [12,13].
Plant hormones are essential for plant growth and development and the plant’s response to abiotic stress [14]. The application of plant hormones, which primarily include abscisic acid (ABA), jasmonic acid (JAs), salicylic acid (SA), and brassicosteroid (BRs), is one important strategy for improving plant salt tolerance [15]. The physiological and molecular mechanisms by which ABA regulates plant tolerance to salt stress have been a research focus in China and globally. Abscisic acid, also known as S-ABA (denoted below by S-ABA), can facilitate the growth of rice leaves when they are under salt stress. Additionally, it can enhance the transpiration efficiency of rice, thereby boosting the salt tolerance of this crop [16]. Wenxin Jiang et al. [17] showed that the application of exogenous S-ABA could trigger the rice filling system’s mechanism. It restrains the generation of reactive oxygen species and adjusts the Na+/K+ equilibrium and hormonal balance within leaves. Consequently, this alleviates salt-stress impact on rice. Certain measures or physiological adaptations lessen negative influence, enabling normal growth and functions, and reducing harm to development, productivity, and health. The study by Chen Guanjie et al. [18] showed that ABA can protect against membrane lipid peroxidation, regulate antioxidant defense, and modulate endogenous hormone balance in rice seedlings under salt stress, helping to counter stress, maintain membrane integrity, enhance antioxidant ability, and ensure hormonal balance for growth. According to the findings of Sripinyowanich et al. [19], the application of S-ABA when rice is under salt stress can boost the growth of rice leaves. This treatment also has the ability to enhance the photosynthetic efficiency of these leaves. As a result, it contributes to elevating the salt tolerance level of rice. In essence, S-ABA plays a crucial role in helping rice better adapt to salt-stress environments by promoting leaf growth and photosynthetic capabilities, which in turn strengthen the plant’s overall ability to withstand the negative impacts of high salt concentrations. In maize plants, exogenous ABA has been found to optimize the gas exchange processes of leaves. It does so by regulating the morphological traits and spatial arrangement of the stomata, which in turn mitigate the negative impacts of NaCl-induced physiological stress on the growth and development of maize [20]. On the other hand, a seed-soaking treatment with S-ABA was found to significantly improve the seed germination and seedling growth of rice under salt stress, thus improving the adaptability of rice under salt stress [21].
To conclude, abscisic acid holds promise for enhancing rice’s salt tolerance. It could be used to boost rice’s ability to endure salt stress. The use of abscisic acid shows potential for improving rice’s high salt tolerance, opening up new ways for cultivating rice in salt-affected areas. However, few studies [17,21] have examined the effects of the number of abscisic acid sprayings applied at different growth stages (seedling and breakage stages) on the physiological characteristics and yield traits of rice under salt stress. To address this gap, this study took the rice variety Huanghuazhan as the experimental material and examined the effects of abscisic acid spraying on the rice phenotype, physiological traits, and yield under salt stress. The objective of this study was to elucidate the physiological mechanism through which abscisic acid eases salt stress in rice, which can be utilized to relieve salt stress encountered during rice cultivation.

2. Materials and Methods

2.1. Experimental Design

(1) Experimental materials and environment: In this experiment, Huanghuazhan provided by the Binhai Agricultural College of Guangdong Ocean University was selected as the rice variety. The experimental agent used was S-ABA produced by Jiangxi Xinruifeng Biochemical Co., Ltd. (Ji’an, China), with the content of its active ingredient being 0.03% and its trade name being “Yakexi”. The experiment was conducted from May to August 2024 in multiple daylight greenhouses at Guangdong Ocean University. The greenhouses were under natural light conditions, with day–night temperature differences maintained at 35/22 ± 2 °C and relative humidity at 60%. The specific geographical location of the university is 21°8′56″ N latitude, 110°17′58″ E longitude, and 20 m altitude.
(2) Seed handling: Rice seed handling for cultivation involved several steps. Initially, appropriate rice seeds were selected and underwent disinfection. They were immersed in a 2.5% sodium hypochlorite solution for a duration of 15 min. Following this, the seeds were rinsed numerous times with distilled water to ensure complete cleanliness. Afterward, the seeds were placed in distilled water and permitted to germinate in darkness. The germination process occurred at a temperature maintained at 30 °C for a period of 24 h. Once germinated, the seeds were sown in plastic, flexible trays measuring 54 cm × 27 cm × 6 cm. These trays were filled with red loam soil for initial seedling growth. When the seedlings developed to the 4-leaf/1-heart stage, they were carefully transplanted by hand. Uniformly grown seedlings were selected and transferred into a leak-tight plastic basin. This basin had an upper diameter of 27.5 cm, a lower diameter of 18.5 cm, and a height of 23 cm. To maintain an adequate water layer, water was regularly added to the plastic basins. Each basin had 8 kg of red loam soil added. In the soil, three holes were made, with two rice seedlings planted in each hole. The distance between each hole was set at 10 cm.
(3) Salt stress and S-ABA treatment: The first foliar spraying of 0.03%-S-ABA (1 mL of 0.03%-S-ABA solution diluted in 99 mL of distilled water, i.e., a 100-fold dilution) was administered to seedlings when they grew to the 3-leaf/1-heart stage at a rate of 0.5 mL per plant. Salt treatment was applied at the 4-leaf/1-heart seedling stage (4-leaf/1-heart seedlings were transplanted directly into plastic pots containing 0.4% NaCl salt soil), and CK and NA (0.4% NaCl) were used to simulate salt-stress conditions. The second foliar spraying of 0.03%-S-ABA (diluted 100 times) was performed when the seedlings grew to the break stage at a rate of 14 mL per plant. A total of 6 treatments were performed: CK (control treatment), S1 (water, spraying S-ABA in the 3-leaf/1-heart stage), S2 (water, spraying S-ABA in the 3-leaf/1-heart stage and again in the break stage), NA (0.4% NaCl), NAS1 (0.4% NaCl, spraying S-ABA in the 3-leaf/1-heart stage), and NAS2 (0.4% NaCl, spraying S-ABA in the 3-leaf/1-heart stage and again in the break stage). This experiment implemented a randomized block design. Samples from two to three leaves of each treatment were collected in the filling stage (5 days after the full heading stage), milk ripening stage (15 days after the full heading stage), and wax ripening stage (25 days after the full heading stage), respectively, for the determination of related morphological and physiological indices. The yield was measured in the final maturity stage. The experiment consisted of six treatments (18 pots per treatment, including some for sampling and 10 pots that maintained at least uniform growth at maturity), three replicas, and a total of 144 barrels.
(4) Fertilization: Fertilization management strategies were formulated in accordance with the field fertilization approach, with the quantity of fertilizer per hectare being a key determinant. Two days prior to transplantation, the base fertilizer was administered. In each plastic basin, the following level of fertilization was used for cultivation treatment: 0.499 g urea (46% N), 0.7128 g superphosphate (60% K2O), and 0.4455 g potassium chloride (15% N and 45% P2O5). A week later, fertilization was applied in the tillering phase of plants, consisting of 0.552 g of nitrogen fertilizer per basin. Subsequent fertilizer applications were adjusted in line with the growth state of seedlings. Regular pesticide spraying was also conducted to safeguard against pests and diseases. The proportion of nitrogen fertilizer application was divided as follows: base fertilizer/fertilizer applied in the tillering phase of plants/fertilizer applied in the spike phase of plants = 4:3:3. Phosphorus fertilizer was used as the sole base fertilizer. For the potassium fertilizer, the ratio of base fertilizer to panicle fertilizer was 1:1. At the tillering phase, during panicle differentiation, 0.70 g of urea and 0.56 g of potassium chloride were added to the rice cultivation. This fertilization was crucial for providing nutrients during these growth phases.

2.2. Determination of Morphology Indices and Methods

2.2.1. Determination of Morphology Indices

During the rice filling stage, twelve similarly grown rice plants were randomly selected. Specific parameters such as plant height, stem thickness, and leaf area (the second-to-last leaf of the main stem and the third-to-last leaf of the main stem) were measured. The plants were placed within a drying oven pre-heated to 105 °C for a duration of 30 min. Subsequently, the oven’s temperature was adjusted to 80 °C and maintained at this setting until the plants reached a constant dry weight state. After this process, the dry weight of the above-ground components of the plants was measured.

2.2.2. Determination of the Chlorophyll Content of the Leaves

Chlorophyll content determination was performed by ethanol extraction [22]. Fresh samples of leaves were cut and mixed, after which 0.02 g of each treatment was weighed and poured into 1.8 mL of anhydrous ethanol and soaked for 24 h in the dark. Each treatment was replicated on three occasions. An ultraviolet–visible spectrophotometer (GENESYS 180, Thermo, Waltham, MA, USA) was employed to ascertain the absorption values of the solution at wavelengths of 665, 649, and 470 nm. The quantities of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoid (Car), and total chlorophyll (Total Chl) were computed. The values of pigment concentrations (mg/L) were worked out in line with the following set of formulas:
Chl a (mg/L) = 13.95D665 − 6.88D649
Chl b (mg/L) = 24.96D649 − 7.32D665
TChl (mg/L) = Chl a + Chl b
Car (mg/g) = (1000D470 − 2.05Chl a − 111.48Chl b)/245

2.2.3. Determination of the Leaf Photosynthetic Parameters

The measurement of photosynthetic parameters such as net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), transpiration rate (Tr), and stomatal conductance (Gs) was conducted from 9:00 a.m. to 11:30 a.m. A portable photosynthetic measurement system (Photosynthesometer apparatus 3051D, Zhejiang Top Cloud-Agritechnologyco., LTD., Zhejiang, China) was utilized for this purpose. The measurements were conducted under the following set of conditions: light intensity amounting to 1000 mmol m−2 s−1, CO2 concentration of 400 mmol mol−1, leaf temperature fixed at 30 °C, relative humidity spanning from 60% to 70%, and airflow rate of 500 mmol s−1.

2.2.4. Active Oxygen Content

The hydrogen peroxide (H2O2) content was measured based on the potassium iodide technique described by Feng et al. [23]. First of all, 500 mg of frozen leaf samples were ground into a homogeneous state in 5 mL of 0.1% trichloroacetic acid (TCA). Subsequently, the resultant mixture was subjected to centrifugation at 12,000× g for 20 min. After this, the supernatant was extracted for the determination of the H2O2 content. The absorbance of the reaction solution was measured at a wavelength of 390 nm. The malondialdehyde (MDA) content was determined by utilizing the thiobarbituric acid method. This involved homogenizing 500 mg of frozen leaf samples in 10 mL of 10% trichloroacetic acid (TCA), then centrifuging at 6000× g for 20 min, and extracting the supernatant for the determination. The absorbance of the reaction solution was measured at wavelengths of 450, 532, and 600 nm. The MDA content was computed using Anastasiou’s formula [24].

2.2.5. Osmoregulatory Substance Content

The content of soluble proteins in the samples was determined using the method described by Kučerová et al. [25]. To begin with, 0.5 g of fresh foliage was accurately weighed and then transformed into a homogenate through the addition of 10 mL of 0.05 mol L−1 phosphate buffer that had been pre-cooled (pH 7.8). The obtained mixture was placed into a centrifuge tube and subjected to centrifugation at a temperature of 4 °C under a centrifugal force of 12,000× g for 20 min. The supernatant that was obtained through this procedure served as the crude protein extract, and it was used for measuring the soluble protein content.

2.2.6. Determination of Enzyme Indexes

Rice leaf samples were quickly frozen using liquid nitrogen and then moved to a freezer maintained at −80 °C for long-term storage. After all samples were collected, 0.5 g of frozen leaf samples were precisely weighed and ground into a homogenized state in 10 mL of pre-cooled 50 mM phosphate buffer solution (with a pH value maintained at 7.8). The homogenized blend was spun at 4 °C under a centrifugal force of 12,000× g for 20 min. Then, the supernatant was carefully retrieved for the assessment of antioxidant enzyme activity. The activity of superoxide dismutase (SOD) was measured using the nitro blue tetrazolium (NBT) approach outlined by Demiral et al. [26], by detecting the optical density values of each solution at a 560 nm wavelength. Regarding the activity of peroxidase (POD), in accordance with the method described by Zhang et al. [27], this was figured out by detecting the rate of guaiacol oxidation at a 470 nm wavelength. With respect to the activity of catalase (CAT), following the method suggested by Feng et al. [28], this was gauged by observing the reduction in absorbance per minute at 240 nm as a result of hydrogen peroxide consumption. Similarly, for the activity of ascorbate peroxidase (APX) and other relevant indicators, in accordance with the method detailed by Wei et al. [29], these were established by the alteration in absorbance per minute at 290 nm.

2.2.7. Determination of Yield and Its Constituent Factors

The investigation of rice yield constituent factors was performed at the maturity stage. In each treatment, ten pots of rice exhibiting similar growth were randomly selected, and a rice plant with an equivalent or comparable average panicle number in all holes was selected as the seed testing sample. The plants were harvested at maturity, air-dried, and evaluated. The number of effective spikes, primary branches, and secondary branches were investigated. After manual threshing and drying, the seeds were separated from full and empty grains by windrowing, the number of full and empty grains were measured, the full and empty grains were weighed, and the fruiting rate (number of full grains/total number of grains × 100%), 1000-grain weight, and yield of individual plants were calculated.

2.3. Statistical Analysis

Microsoft Excel 2019 was used to process the original data. Means were compared using a one-way ANOVA with the factors being whether or not they were subjected to salt stress and the period of S-ABA application. Significant differences were further analyzed using Duncan’s test. In analyzing the parameters, the means of three replicates (n = 3) ± S.E were performed for each treatment. Microsoft Excel 2019 and Origin 2021 software were used for graphing.

3. Results

3.1. Effect of Abscisic Acid on Rice Morphogenesis Under Salt Stress

As presented clearly in Table 1, the growth and development of rice plants that were subjected to salt-stress conditions faced a substantial degree of inhibition. The adverse effects of salt stress permeated multiple vital aspects of the rice’s growth cycle. Compared with CK rice, salt-treated (NA) rice exhibited a significantly reduced plant height by 16.51%, stem thickness by 13.57%, leaf area by 67.27%, and above-ground dry weight by 50.72%. Under non-salt stress, S-ABA (S1, S2) treatment had no significant effect on rice growth in the filling stage, but under salt stress S-ABA (NAS1, NAS2) treatment increased the plant height, stem thickness, leaf area, and above-ground dry weight, with NAS2 producing significant effects. The plant height, stem thickness, leaf area, and dry-matter weight when treated with NAS2 were significantly increased by 13.54%, 26.44%, 82.06%, and 52.49%, respectively, compared with NA.

3.2. Effects of Abscisic Acid on Photosynthetic Pigments of Rice Under Salt Stress

As shown in Figure 1, salt stress significantly affected the photosynthetic pigment content in rice leaves. During the growth stage, the chlorophyll content under salt stress increased first, then decreased. Compared with CK, the contents of chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll were significantly reduced in the wax ripening stage under salt stress, with decreases of 8.83%, 8.87%, 10.19%, and 17.71%, respectively. Under non-salt-stress conditions, S-ABA (S1, S2) treatment increased the photosynthetic pigment content of rice in the milk ripening stage and wax ripening stage, with the S2 treatment significantly increasing the chlorophyll b content in the milk ripening stage and filling stage by 53.76% and 10.58%, respectively. Under salt stress, the NAS2 treatment significantly increased the photosynthetic pigment content in the rice filling and wax ripening stages. The chlorophyll a content under NAS2 was increased by 29.50% and 63.57% in the filling and wax ripening stages, respectively. The chlorophyll b content was significantly increased by 30.41% and 79.00%, respectively. The carotenoid content was significantly increased by 30.04% and 42.80%, respectively. The total chlorophyll content was significantly increased by 41.79% and 75.34%, respectively.

3.3. Effects of Abscisic Acid on the Photosynthesis of Rice Under Salt Stress

As depicted clearly in Figure 2, the presence of salt stress had a discernible inhibitory effect on Pn, Tr, Ci, and Gs within the leaves of rice plants. To be more specific, Pn experienced a notable decline of 45.18%, Tr decreased by 32.59%, Ci was reduced by 3.62%, and Gs dropped by 23.81%.
As shown in Figure 2, salt stress significantly inhibited Pn, Tr, Ci, and Gs in rice leaves by 45.18%, 32.59%, 3.62%, and 23.81%, respectively. Under non-salt stress, S-ABA (S1, S2) treatment increased Tr, Gs, and Ci, with the effects of S2 reaching statistical significance, with increases of 59.10%, 72.62%, and 5.32%, respectively. Under salt stress, S-ABA (NAS1, NAS2) treatment significantly increased Pn, Tr, and Gs in rice leaves, and the effects of NAS2 were more significant, with increases of 127.60%, 143.18%, and 112.50%, respectively.

3.4. Effects of Abscisic Acid on the Antioxidant System of Rice Under Salt Stress

As shown in Figure 3, it becomes manifest that the activities of antioxidant oxidases in the leaves of rice plants, when subjected to salt stress and S-ABA, display dissimilarities. Compared with CK, the SOD, APX, CAT, and POD activities were decreased by 43.73%, 6.25%, 9.30%, and 29.43%, respectively, under salt treatment (NA). Under non-salt stress, S-ABA (S1, S2) treatment induced increases in APX and POD in the filling stage, milk ripening stage, and wax ripening stage, and SOD in the milk ripening stage and wax ripening stage, as compared with CK, but these effects were not significant. In contrast, CAT enzyme activity in the milk ripening stage was significantly decreased by 28.12% and 28.30%, respectively. Under salt stress, the SOD, APX, CAT, and POD activities under S-ABA (NAS1, NAS2) treatment were increased compared with those under NA. The NAS2 treatment produced the greatest increases compared with NA. The SOD activity of NAS2 treatment increased by 46.63%, 14.01%, and 65.28% in the filling, milk, and wax stages, respectively, the APX activity increased by 53.15%, 55.51%, and 34.28%, respectively, and the POD activity increased by 8.33%, 32.46%, and 55.42%, respectively. The CAT activity increased by 20.06%, 69.13%, and 47.66%, respectively.

3.5. Effects of Abscisic Acid on Oxidative Metabolism Under Salt Stress

As shown in Figure 4, under salt stress, the H2O2 and MDA contents in rice leaves in the filling stage, milk ripening stage, and wax ripening stage increased sharply, by 32.09%, 20.83%, and 18.76%, and 12.38%, 9.98%, and 11.27%, respectively. Under non-salt stress, S-ABA (S1, S2) treatment decreased the H2O2 content in rice leaves; this difference was not significant. In contrast, the content of MDA underwent an upward trend. Specifically, under the S2 treatment during the filling stage, milk ripening stage, and wax ripening stage, the increases achieved statistical significance. The augmentations were, respectively, 3.86% in the filling stage, 4.87% in the milk ripening stage, and 8.69% in the wax ripening stage. Under salt stress, both the S-ABA (NAS1 and NAS2) treatments significantly reduced the H2O2 content of rice leaves by 52.18%, 14.89%, and 6.05%, and significantly reduced MDA content by 11.66%, 12.49%, and 10.07% in the filling stage, milk ripening stage, and wax ripening stage, respectively. The NAS2 treatment exhibited the greatest effect.

3.6. Effects of Abscisic Acid on Osmoregulatory Substances Under Salt Stress

Plants’ response mechanisms to stress involve an upsurge in the generation of osmoregulatory substances. When confronted with stress, plants tend to boost the production of osmoregulatory substances as a means of adaptation. As shown in Figure 5, salt stress reduced the soluble protein content in rice leaves in the filling stage, milk ripening stage, and wax ripening stage, by 2.90%, 2.03%, and 0.10%, respectively. Under non-salt stress, S-ABA (S1, S2) treatment decreased the soluble protein content of rice in the filling stage and milk ripening stage, with S1 and S2 reaching statistical significance in the milk ripening stage, declining by 1.08% and 0.78%, respectively. Under salt stress, S-ABA (NAS1, NAS2) treatment significantly promoted the synthesis of soluble protein in the filling stage, milk ripening stage, and wax ripening stage, with increases of 2.21% and 2.60%, 1.98% and 2.35%, and 0.87% and 1.72%, respectively. NAS2 produced the largest increases.

3.7. Effects of Abscisic Acid on Rice Yield and Its Constituent Indices Under Salt Stress

The degree of grain development is the key to estimating rice yield. As can be seen from Table 2, salt stress reduced the effective panicle number, the number of branches, the number of spikelets per panicle, the number of filled grains, the 1000-grain weight, and the yield of rice; the yield decreased by 27.75%. Under non-salt stress, S-ABA (S2) treatment increased the effective panicle number, the number of primary branches, the number of secondary branches, the number of spikelets per panicle, the percentage of filled grains, the 1000-grain weight, and the yield by 9.33%, 5.56%, 29.54%, 5.08%, 19.21%, 18.06%, and 10.45%, respectively. Among these, the 1000-grain weight, percentage of filled grains, and yield reached statistical significance. Under salt stress, S-ABA (NAS1 and NAS2) treatment increased rice yield and its constituent indices. The number of spikelets per panicle increased by 9.48% and 24.77%, percentage of filled grains by 1.35% and 26.62%, 1000-grain weight by 11.65% and 21.48%, and yield by 14.84% and 29.29% in NAS1 and NAS2 treatments, with the effects of NAS2 reaching statistical significance.

4. Discussion

4.1. Effects of Exogenous Abscisic Acid on the Growth and Development of Rice Under Salt Stress

Previous studies have highlighted that salt stress inhibits the normal growth of rice seedlings, as evidenced by a reduction of leaf area, plant height, and biomass accumulation [30]. In this study, the impact of salt stress was notable. It led to a substantial decline in multiple aspects of rice, including the plant’s height, the thickness of its stems, the area of its leaves, and the dry weight of the above-ground parts. This may be due to the fact that salt stress produces osmotic stress, which interferes with the normal metabolic processes of the plant, leading to the blockage of cellular water uptake, the reduction of leaf relative water content, growth retardation, and the reduction of biomass accumulation. Foliar spraying of S-ABA effectively alleviated the inhibitory effect of salt stress on the growth of rice, and increased the plant height, stem thickness, leaf area, and above-ground dry weight to different degrees. Among these, NAS2 reached a significant level, which indicated that the regulatory effect of two S-ABA sprayings was better than that of one spraying. Similar results were previously observed in trifoliate oranges [31] and wheat [32].

4.2. Effects of Exogenous Abscisic Acid on Rice Photosynthesis Under Salt Stress

Photosynthesis serves as the fundamental cornerstone for determining crop yield. Chlorophyll functions in the processes of light energy absorption, transfer, and conversion. The amount of chlorophyll present within plants can effectively mirror their photosynthetic capabilities [33]. X. Wang et al. [34] argued that the low osmotic potential caused by salt stress leads to leaf stomatal conductance limitations, thus inhibiting photosynthesis in rice leaves. Studies have also shown that while salt stress accelerates the degradation of chlorophyll in rice, it also reduces the stability of the thylakoid membrane and the absorption capacity of chloroplasts for light energy, thus reducing the photosynthetic rate of rice [35]. In this study, the chlorophyll a, b, carotenoids, and total chlorophyll contents first increased and then decreased under salt stress as the reproductive period progressed. This finding aligns with the results obtained by Qiu et al. [36]. This might be because the vast majority of chlorophyll a molecules and all chlorophyll b molecules play a role in collecting light energy, and salt stress disrupts chlorophyll binding to chloroplast proteins, which leads to an increase in free chlorophyll. The decrease in the chlorophyll content of leaves under salt stress in the middle and late stages of the experiment (wax ripening stage) may be due to the gradual cleavage of the chlorophyll structure and the slowing down of the rate of chlorophyll synthesis. Conversely, during the filling and wax ripening phases of rice, the NAS2 treatment led to a substantial elevation in the content of photosynthetic pigments. This phenomenon could potentially be attributed to the fact that under adverse stress situations the lutein cycle and the biosynthesis of ABA might engage in competition for carotenoids. Given the restricted distribution of carotenoids to the lutein cycle, plants become more vulnerable to the detrimental effects of intense light. In contrast, the application of exogenous ABA may mitigate the competition of the lutein cycle for carotenoids. As a result, it lessens the excessive harm inflicted by light on plants experiencing salt stress. This finding is in harmony with the outcomes of the present experiment, in which NAS2 under salt-stress conditions notably augmented the chlorophyll content [37].
The impact of salt stress on biomass accumulation is strikingly inhibitory. This inhibitory effect, as a consequence, brings about a shrinkage in leaf area and a drop in photosynthetic parameters [38,39]. Hu [31] et al. indicated that photosynthetic parameters, actual photochemical efficiency, and photochemical burst coefficients are significantly reduced under salt stress. Comparable results were obtained in this study where salt stress significantly reduced Pn, Gs, and Tr. Factors affecting photosynthesis can be divided into two types: stomatal restriction and non-stomatal restriction. When the change law of the intercellular CO2 concentration is consistent with the change law of the net photosynthetic rate and stomatal conductance, it is considered that stomatal regulation is involved [40]. If the change law is inconsistent, it is considered to be non-stomatal regulation [41]. Therefore, the decrease in Pn in rice leaves under salt stress can be attributed to the non-stomatal restriction caused by the reduction in chloroplast activity.
Abscisic acid exercises its function in regulating the water status of plants through guard cells. This regulatory mechanism helps plants to combat the adverse effects that salt damage has on plant growth, photosynthesis processes, and the translocation of assimilates. When ABA is applied via foliar spraying, it induces the closure of stomata and brings about a reduction in the transpiration rate. Therefore, it has the potential to function as an anti-transpiration agent [42]. In the present research, under conditions of salt stress, applying ABA through foliar spraying led to a significant elevation in Pn, Tr, and Gs; on the one hand, this might be driven by the increase in stomatal conductance, as Gs induced reopening of the stomata and improved their function, which in turn increased the transpiration rate and maintained the steady state of net photosynthetic rate under salt stress; on the other hand, this might be due to the fact that ABA efficiently increased the content of chlorophyll, which in turn enhanced plant photosynthesis [43]. This is comparable to the findings of Xie et al. [44]. Nonetheless, additional research efforts are essential to comprehensively elucidate the mechanisms through which abscisic acid modulates the chlorophyll content and photosynthetic processes in rice seedlings when subjected to salt stress.

4.3. Effects of Exogenous Abscisic Acid on the Antioxidant System of Rice Under Salt Stress

An imbalance in reactive oxygen species metabolism induced by salt stress is a common manifestation of plant injury. An overabundance of reactive oxygen species has the potential to trigger membrane lipid peroxidation. This is because when these reactive species accumulate beyond normal levels, they initiate a series of chemical reactions that target the lipids in cell membranes. Hence, the integrity of the membrane’s lipid structure is disrupted, which can have detrimental effects on cell function and viability. MDA, which stands as the principal outcome of membrane lipid peroxidation, is regarded as a biological indicator for assessing the extent of lipid peroxidation as well as the damage inflicted upon plasma membranes and cell organelles [45]. When plants are subjected to salt stress, they generate an overabundance of reactive oxygen species. This results in the build-up of membrane lipid peroxides such as MDA. Such peroxides undermine the integrity of the cell membrane, which in turn brings about physiological and metabolic disruptions and restricts the growth of plants [46]. Moreover, an over-accumulation of H2O2 gives rise to increased lipid peroxidation. This, in turn, causes the leakage of cellular components [47]. In the course of this research, under the influence of salt stress, the levels of H2O2 and MDA in rice leaves witnessed an upward trend. Conversely, the amounts of SOD, APX, CAT, and POD exhibited a decline. This set of changes implies that salt stress induced rice to amass a greater quantity of reactive oxygen species, thereby inflicting damage upon the antioxidant system. This is comparable to the findings of Vaidyanathan et al. [48]. Upon the application of S-ABA through spraying, the activities of antioxidant enzymes such as SOD, APX, CAT, and POD in the leaves of rice under salt stress were remarkably elevated in comparison with those solely subjected to salt treatment. Additionally, the levels of MDA and H2O2 were maintained at relatively lower values, and the effect of two S-ABA sprayings was better than that of one spraying. Previous investigations have revealed that ABA has the ability to stimulate the expression of antioxidant enzymes in plants. In doing so, it can mitigate the oxidative harm brought about by stress conditions, as numerous previous studies have pointed out [31,46,49]. The results obtained indicate that exogenous abscisic acid lessens the damage brought about by salt stress in rice. Through the activation of the antioxidant system, it clears away excessive reactive oxygen species and curbs membrane lipid peroxidation, consequently improving the capacity of rice to tolerate salt. However, the mechanism by which abscisic acid produces a series of complex effects to improve the salt tolerance of plants has not been unanimously determined and is an important direction for future research.

4.4. Effects of Exogenous Abscisic Acid on Osmotic Regulatory Substances in Rice Leaves Under Salt Stress

Under salt stress, plants can adapt to unfavorable conditions by synthesizing different osmotic substances through osmoregulation to help maintain water balance in the body. When plants are in a normal growth environment, the amount of osmoprotective substances is relatively low, but when they are in a salt-stressed environment, the osmotic pressure becomes unbalanced, and plants maintain osmotic balance by synthesizing more soluble substances. Xu et al. [50] showed that the difference in soluble protein content between salt-stress treatments and controls was not significant, and that a specific concentration of ABA significantly increased soluble protein synthesis after treatment. The outcomes of the current research demonstrated that, under salt-stress conditions, S-ABA treatments both led to an augmentation in the soluble protein content within rice leaves. This increase played a part in sustaining a lower intracellular osmotic potential and also in stabilizing the structures of proteins and membranes.

4.5. Effects of Exogenous Abscisic Acid on Rice Yield and Yield Composition Under Salt Stress

The impacts of salt stress on rice yield were chiefly shown through substantial decreases in the count of effective panicles, the quantity of branches, the number of spikelets per panicle, the proportion of filled grains, and the weight of 1000 grains. It is indicated by this that salt stress substantially restricts the rice’s capacity for storing resources and its traits related to storage enrichment. Consequently, this leads to a decline in the yield of rice [51]. Li Hongyu et al. [52] discovered that the weight of the panicle was the principal factor contributing to the decline in rice yield. Additionally, the reduction in the numbers of both primary and secondary branches associated with the panicle count was the main cause behind the decrease in panicle weight. Ali et al. [53] found that salt stress in the seedling stage directly led to a decline in rice yield after maturity, and yield components and other indicators were seriously affected. In this experimental setup, salt stress led to a notable reduction in the 1000-grain weight, the number of spikelets per panicle, the percentage of filled grains, and the number of primary branches, thereby substantially impeding rice yield. When exogenous S-ABA was applied under salt-stress conditions, it brought about an increase in the effective spike count and the number of branching peduncles in rice. This finding suggests that S-ABA can safeguard the progression of rice spike differentiation and boost the quantity of branching peduncles. Under salt-stress circumstances, applying S-ABA via two sprayings led to a substantial rise in the quantity of grains per spike, the fruiting rate, the 1000-grain weight, and the yield of rice when contrasted with the group merely receiving salt treatment. This may be attributed to the fact that abscisic acid favors the formation of pollen mother cells and reduces septation, thus increasing the fruiting rate. In addition, S-ABA may also control rice nutrient growth and increase the transport of assimilates to seeds, which could have beneficial effects on the yield of rice [54]. Significantly, in the presence of salt stress, applying S-ABA through two sprayings exhibited a more pronounced impact on augmenting the yield as opposed to a single spraying.

5. Conclusions

Salt stress inhibited the rice plant growth, decreased the plant height, stem thickness, leaf area, and above-ground dry weight in the filling stage, and reduced chlorophyll synthesis in the filling and wax ripening stages, but increased it in the milk ripening stages. At the same time, salt stress inhibited the photosynthetic process of rice, destroyed the stability of the photosynthetic structure, reduced the activity of antioxidant enzymes, aggravated membrane lipid peroxidation, and caused salt damage to rice, thus reducing rice yield. Exogenous abscisic acid sprayed once or twice enhanced the osmoregulation (soluble protein) potential of rice leaves under salt stress by enhancing the antioxidant enzyme activity (SOD, POD, CAT, and APX), thereby reducing the membrane lipid peroxidation level, improving the photosynthetic capacity of rice, and alleviating the damage to rice plants under salt stress. The yield loss of Huanghuazhan under salt stress was alleviated. Two applications of S-ABA at the three-leaf/one-heart stage and break stage under salt stress were the most effective, suggesting that two applications of S-ABA are more effective in reducing the damage of salt stress on rice and increasing rice yield.

Author Contributions

X.W. was responsible for the methodology, data management, investigation, formal analysis, and writing the original draft. G.M. contributed to the methodology and conceptualization, acquisition of funding, and administration of the project. N.F. contributed to the methodology and conceptualization, acquisition of funding, and administration of the project. D.Z. aided in the conceptualization and acquisition of funding and resources. H.Z. analyzed the data, prepared figures and/or tables, authored or reviewed drafts of the article, and approved the final draft. J.L. performed the experiments, prepared figures and/or tables, and approved the final draft. J.W. performed the experiments, prepared figures and/or tables, and approved the final draft. W.S. analyzed the data, prepared figures and/or tables, and approved the final draft. B.X. analyzed the data, prepared figures and/or tables, and approved the final draft. Y.H. analyzed the data, prepared figures and/or tables, and approved the final draft. All authors have read and agreed to the published version of the manuscript.

Funding

Guangdong Provincial Department of Education General Colleges and Universities Key Areas of Specialization (2021ZDZX4027), the College of Coastal Agricultural Sciences Technology Research Center of Guangdong Ocean University (230420020), and the Guangdong Provincial Department of Education graduate Innovation Forum (2022XSLT036).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Lou, Y.; Xu, M.; Wang, W.; Sun, X.; Zhao, K. Return rate of straw residue affects soil organic C sequestration by chemical fertilization. Soil Tillage Res. 2011, 113, 70–73. [Google Scholar] [CrossRef]
  2. Chinnusamy, V.; Jagendorf, A.; Zhu, J.K. Understanding and improving salt tolerance in plants. Crop Sci. 2005, 45, 437–448. [Google Scholar] [CrossRef]
  3. Negacz, K.; Malek, Ž.; de Vos, A.; Vellinga, P. Saline soils worldwide: Identifying the most promising areas for saline agriculture. J. Arid Environ. 2022, 203, 104775. [Google Scholar] [CrossRef]
  4. Li, J.G.; Pu, L.J.; Zhu, M.; Zhang, R. The Present Situation and Hot Issues in the Salt-affected Soil Research. Acta Geogr. Sin. 2012, 67, 1233–1245. [Google Scholar]
  5. Thitisaksakul, M.; Tananuwong, K.; Shoemaker, C.F.; Chun, A.; Tanadul, O.-u.-m.; Labavitch, J.M.; Beckles, D.M. Effects of timing and severity of salinity stress on rice (Oryza sativa L.) yield, grain composition, and starch functionality. J. Agric. Food Chem. 2015, 63, 2296–2304. [Google Scholar] [CrossRef] [PubMed]
  6. Grattan, S.R.; Zeng, L.; Shannon, M.C.; Roberts, S.R. Rice is more sensitive to salinity than previously thought. Calif. Agric. 2002, 56, 189–195. [Google Scholar] [CrossRef]
  7. Khatun, S.; Flowers, T. Effects of salinity on seed set in rice. Plant Cell Environ. 1995, 18, 61–67. [Google Scholar] [CrossRef]
  8. Jia, X.-M.; Wang, H.; Svetla, S.; Zhu, Y.-F.; Hu, Y.; Cheng, L.; Zhao, T.; Wang, Y.-X. Comparative physiological responses and adaptive strategies of apple Malus halliana to salt, alkali and saline-alkali stress. Sci. Hortic. 2019, 245, 154–162. [Google Scholar] [CrossRef]
  9. Chapman, J.M.; Muhlemann, J.K.; Gayomba, S.R.; Muday, G.K. RBOH-dependent ROS synthesis and ROS scavenging by plant specialized metabolites to modulate plant development and stress responses. Chem. Res. Toxicol. 2019, 32, 370–396. [Google Scholar] [CrossRef] [PubMed]
  10. Ponce, K.S.; Guo, L.; Leng, Y.; Meng, L.; Ye, G. Advances in sensing, response and regulation mechanism of salt tolerance in rice. Int. J. Mol. Sci. 2021, 22, 2254. [Google Scholar] [CrossRef]
  11. Zhang, R.; Wang, Y.; Hussain, S.; Yang, S.; Li, R.; Liu, S.; Chen, Y.; Wei, H.; Dai, Q.; Hou, H. Study on the effect of salt stress on yield and grain quality among different rice varieties. Front. Plant Sci. 2022, 13, 918460. [Google Scholar] [CrossRef] [PubMed]
  12. Khan, M.I.R.; Ashfaque, F.; Chhillar, H.; Irfan, M.; Khan, N.A. The intricacy of silicon, plant growth regulators and other signaling molecules for abiotic stress tolerance: An entrancing crosstalk between stress alleviators. Plant Physiol. Biochem. 2021, 162, 36–47. [Google Scholar] [CrossRef]
  13. Desta, B.; Amare, G. Paclobutrazol as a plant growth regulator. Chem. Biol. Technol. Agric. 2021, 8, 1. [Google Scholar] [CrossRef]
  14. Taheri, Z.; Vatankhah, E.; Jafarian, V. Methyl jasmonate improves physiological and biochemical responses of Anchusa italica under salinity stress. S. Afr. J. Bot. 2020, 130, 375–382. [Google Scholar] [CrossRef]
  15. Dar, T.A.; Uddin, M.; Khan, M.M.A.; Hakeem, K.; Jaleel, H. Jasmonates counter plant stress: A review. Environ. Exp. Bot. 2015, 115, 49–57. [Google Scholar] [CrossRef]
  16. Ren, F.; Zhang, R.J.; Chen, Q.; Bai, Y.; Huang, F.; Li, X. Progress in ABA and SA Improving Plant Drought Resistance and Salt Resistance. Biotechnol. Bull. 2012, 29, 17–21. [Google Scholar]
  17. Jiang, W.; Wang, X.; Wang, Y.; Du, Y.; Zhang, S.; Zhou, H.; Feng, N.; Zheng, D.; Ma, G.; Zhao, L. S-ABA Enhances Rice Salt Tolerance by Regulating Na+/K+ Balance and Hormone Homeostasis. Metabolites 2024, 14, 181. [Google Scholar] [CrossRef] [PubMed]
  18. Chen, G.; Zheng, D.; Feng, N.; Zhou, H.; Mu, D.; Zhao, L.; Shen, X.; Rao, G.; Meng, F.; Huang, A. Physiological mechanisms of ABA-induced salinity tolerance in leaves and roots of rice. Sci. Rep. 2022, 12, 8228. [Google Scholar] [CrossRef] [PubMed]
  19. Sripinyowanich, S.; Klomsakul, P.; Boonburapong, B.; Bangyeekhun, T.; Asami, T.; Gu, H.; Buaboocha, T.; Chadchawan, S. Exogenous ABA induces salt tolerance in indica rice (Oryza sativa L.): The role of OsP5CS1 and OsP5CR gene expression during salt stress. Environ. Exp. Bot. 2013, 86, 94–105. [Google Scholar] [CrossRef]
  20. Zhang, H.; Wu, Z.; Fu, W.; Ye, J.; Ma, J.; Hao, L.; Chang, Z.; Zheng, Y. Effect of exogenous abscisic acid (ABA) on the growth, stomatal traits, and photosynthesis of maize seedings under NaCl stress. Chin. J. Ecol. 2021, 40, 2005–2015. [Google Scholar]
  21. Huang, A.Q.; Ma, G.H.; Zhao, L.M.; Jiang, W.X.; Feng, N.J.; Zheng, D.F.; Zhan, P.F.; Zou, W.L. Effects of S-ABA Soaking of Seeds on Growth and Physiological Characteristics of Rice Seedings Under Salt Stress. Hybrid Rice 2023, 38, 124–134. [Google Scholar] [CrossRef]
  22. Lichtenthaler, H.K. Chlorophylls and carotenoids: Pigments of photosynthetic biomembranes. In Methods in Enzymology; Academic Press: Cambridge, MA, USA, 1987; Volume 148, pp. 350–382. [Google Scholar]
  23. Feng, N.; Yu, M.; Li, Y.; Jin, D.; Zheng, D. Prohexadione-calcium alleviates saline-alkali stress in soybean seedlings by improving the photosynthesis and up-regulating antioxidant defense. Ecotox Environ. Safe 2021, 220, 112369. [Google Scholar] [CrossRef] [PubMed]
  24. Anastasiou, E.; Lorentz, K.O.; Stein, G.J.; Mitchell, P.D. Prehistoric schistosomiasis parasite found in the Middle East. Lancet Infect. Dis. 2014, 14, 553–554. [Google Scholar] [CrossRef] [PubMed]
  25. Kučerová, K.; Henselová, M.; Slováková, Ľ.; Hensel, K. Effects of plasma activated water on wheat: Germination, growth parameters, photosynthetic pigments, soluble protein content, and antioxidant enzymes activity. Plasma Process. Polym. 2019, 16, 1800131. [Google Scholar] [CrossRef]
  26. Demiral, T.; Türkan, I. Comparative lipid peroxidation, antioxidant defense systems and proline content in roots of two rice cultivars differing in salt tolerance. Environ. Exp. Bot. 2005, 53, 247–257. [Google Scholar] [CrossRef]
  27. Zhang, L.; Pei, Y.; Wang, H.; Jin, Z.; Liu, Z.; Qiao, Z.; Fang, H.; Zhang, Y. Hydrogen sulfide alleviates cadmium-induced cell death through restraining ROS accumulation in roots of Brassica rapa L. ssp. pekinensis. Oxidative Med. Cell. Longev. 2015, 2015, 804603. [Google Scholar] [CrossRef] [PubMed]
  28. Feng, B.; Li, G.; Islam, M.; Fu, W.; Zhou, Y.; Chen, T.; Tao, L.; Fu, G. Strengthened antioxidant capacity improves photosynthesis by regulating stomatal aperture and ribulose-1, 5-bisphosphate carboxylase/oxygenase activity. Plant Sci. 2020, 290, 110245. [Google Scholar] [CrossRef] [PubMed]
  29. Wei, M.-Y.; Liu, J.-Y.; Li, H.; Hu, W.-J.; Shen, Z.-J.; Qiao, F.; Zhu, C.-Q.; Chen, J.; Liu, X.; Zheng, H.-L. Proteomic analysis reveals the protective role of exogenous hydrogen sulfide against salt stress in rice seedlings. Nitric Oxide 2021, 111, 14–30. [Google Scholar] [CrossRef]
  30. Kenawy, E.-R.; Rashad, M.; Hosny, A.; Shendy, S.; Gad, D.; Saad-Allah, K.M. Enhancement of growth and physiological traits under drought stress in Faba bean (Vicia faba L.) using nanocomposite. J. Plant Interact. 2022, 17, 404–418. [Google Scholar] [CrossRef]
  31. Hu, C.-H.; Zheng, Y.; Tong, C.-L.; Zhang, D.-J. Effects of exogenous melatonin on plant growth, root hormones and photosynthetic characteristics of trifoliate orange subjected to salt stress. Plant Growth Regul. 2022, 97, 551–558. [Google Scholar] [CrossRef]
  32. Parveen, A.; Ahmar, S.; Kamran, M.; Malik, Z.; Ali, A.; Riaz, M.; Abbasi, G.H.; Khan, M.; Sohail, A.B.; Rizwan, M. Abscisic acid signaling reduced transpiration flow, regulated Na+ ion homeostasis and antioxidant enzyme activities to induce salinity tolerance in wheat (Triticum aestivum L.) seedlings. Environ. Technol. Innov. 2021, 24, 101808. [Google Scholar] [CrossRef]
  33. Yu, M.L.; Zuo, G.Q.; Li, Y.; Zheng, D.F.; Feng, N.J. Effects of prohexadione-calcium on photosynthetic characteristics and protective enzyme activity of soybean seedings under saline-alkali stress. Chin. J. Oil Crop Sci. 2019, 41, 741–749. [Google Scholar]
  34. Wang, X.; Wang, W.; Huang, J.; Peng, S.; Xiong, D. Diffusional conductance to CO2 is the key limitation to photosynthesis in salt-stressed leaves of rice (Oryza sativa). Physiol. Plant. 2018, 163, 45–58. [Google Scholar] [CrossRef] [PubMed]
  35. Li, H.; Chen, W.; Li, Q. Responses of rice leaf photosynthetic parameters to light in tensity under NaCl stress. Chin. J. Appl. Ecol. 2006, 17, 1588–1592. [Google Scholar]
  36. Qiu, G.J.; Yu, M.; Hu, W.X.; Chen, K.; Yao, Z.Y. Effects of salt stress on growth and physiological and biochemical characteristics of Lagerstroemia india “Pink Velour”. Jiangsu Agric. Sci. 2018, 46, 123–126. [Google Scholar]
  37. Zhu, S.-Q.; Chen, M.-W.; Ji, B.-H.; Jiao, D.-M.; Liang, J.-S. Roles of xanthophylls and exogenous ABA in protection against NaCl-induced photodamage in rice (Oryza sativa L) and cabbage (Brassica campestris). J. Exp. Bot. 2011, 62, 4617–4625. [Google Scholar] [CrossRef] [PubMed]
  38. He, C.; Yan, J.; Shen, G.; Fu, L.; Holaday, A.S.; Auld, D.; Blumwald, E.; Zhang, H. Expression of an Arabidopsis vacuolar sodium/proton antiporter gene in cotton improves photosynthetic performance under salt conditions and increases fiber yield in the field. Plant Cell Physiol. 2005, 46, 1848–1854. [Google Scholar] [CrossRef]
  39. Harizanova, A.; Koleva-Valkova, L. Effect of silicon on photosynthetic rate and the chlorophyll fluorescence parameters at hydroponically grown cucumber plants under salinity stress. J. Cent. Eur. Agric. 2019, 20, 953–960. [Google Scholar] [CrossRef]
  40. Ling, Y.H.; Zhou, Y.; Jing, B.; Li, C.L.; Xiao, E.S.; Wang, Z.H. Effects of salt stress on growth and physiological characteristics of sunflower at seeding stage. Agric. Res. Arid Areas 2019, 37, 139–145. [Google Scholar]
  41. Ye, Z.P.; Zheng, Z.; Kang, H.J.; Wang, F.B.; An, T.; Duan, S.H. Stomatal and non-stomatal limitations on photosynthesis of flag leaf of medium mature indica rice at early earring stage under natural conditions. Chin. J. Ecol. 2019, 38, 1004–1012. [Google Scholar]
  42. Shabala, S.; Cuin, T.A. Potassium transport and plant salt tolerance. Physiol. Plant. 2008, 133, 651–669. [Google Scholar] [CrossRef]
  43. Acosta-Motos, J.R.; Ortuño, M.F.; Bernal-Vicente, A.; Diaz-Vivancos, P.; Sanchez-Blanco, M.J.; Hernandez, J.A. Plant responses to salt stress: Adaptive mechanisms. Agronomy 2017, 7, 18. [Google Scholar] [CrossRef]
  44. Xie, Y.; Sun, G.; Wang, L.; Tang, Y. Effects of spraying abscisic acid on photosynthetic physiology of lettuce seedlings under salt stress. In Proceedings of IOP Conference Series: Earth and Environmental Science, Paris, France, 7–9 February 2018; p. 052011. [Google Scholar]
  45. Theerakulpisut, P.; Nounjan, N.; Kumon-Sa, N. Spermidine priming promotes germination of deteriorated seeds and reduced salt stressed damage in rice seedlings. Not. Bot. Horti Agrobot. Cluj-Napoca 2021, 49, 12130. [Google Scholar] [CrossRef]
  46. Liu, X.-L.; Zhang, H.; Jin, Y.-Y.; Wang, M.-M.; Yang, H.-Y.; Ma, H.-Y.; Jiang, C.-J.; Liang, Z.-W. Abscisic acid primes rice seedlings for enhanced tolerance to alkaline stress by upregulating antioxidant defense and stress tolerance-related genes. Plant Soil 2019, 438, 39–55. [Google Scholar] [CrossRef]
  47. Ahanger, M.A.; Mir, R.A.; Alyemeni, M.N.; Ahmad, P. Combined effects of brassinosteroid and kinetin mitigates salinity stress in tomato through the modulation of antioxidant and osmolyte metabolism. Plant Physiol. Biochem. 2020, 147, 31–42. [Google Scholar] [CrossRef]
  48. Vaidyanathan, H.; Sivakumar, P.; Chakrabarty, R.; Thomas, G. Scavenging of reactive oxygen species in NaCl-stressed rice (Oryza sativa L.)—Differential response in salt-tolerant and sensitive varieties. Plant Sci. 2003, 165, 1411–1418. [Google Scholar] [CrossRef]
  49. Bhaskara, G.B.; Nguyen, T.T.; Yang, T.-H.; Verslues, P.E. Comparative analysis of phosphoproteome remodeling after short term water stress and ABA treatments versus longer term water stress acclimation. Front. Plant Sci. 2017, 8, 523. [Google Scholar] [CrossRef] [PubMed]
  50. Liu, X.; Lin, B.Y.; Li, C.X.; Wu, H.Q.; Zu, Y.D.; Zhong, L.M. Effects of exogenous abscisic acid on physiological characteristics of eggplant seedlings under salt stress. J. Henan Agric. Univ. 2020, 54, 231–236. [Google Scholar]
  51. Zhang, W.; Zhao, X.H.; Zhou, M.Y.; Guo, H.J.; Zhang, L.Y.; Fu, Z.Q.; Long, P. Effects of Salt Stress on Stress Resistance Physiology, Yield and Quality of Sea Rice. Mol. Plant Breed. 1–12. Available online: https://link.cnki.net/urlid/46.1068.S.20230301.1422.019 (accessed on 3 December 2024).
  52. Li, H.Y.; Pan, S.J.; Qian, Y.D.; Ma, Y.; Si, Y.; Gao, S.; Zheng, G.P.; Jiang, Y.W.; Zhou, J. Effects of saline-alkali stress on yield and quality of rice in cold region. J. South. Agric. 2015, 46, 2100–2105. [Google Scholar]
  53. Yousaf Ali, Y.A.; Aslam, Z.; Awan, A.; Hussain, F.; Cheema, A. Screening rice (Oryza sativa L.) lines/cultivars against salinity in relation to morphological and physiological traits and yield components. Int. J. Agric. Biol. 2004, 6, 572–575. [Google Scholar]
  54. Chen, S.R.; Yu, Y.H. Research of Applying Combinations of Humic Acid Microbial Fertilizer, S-Abscisic Acid and Titanium in Rice Production. Chem. Fertil. Ind. 2018, 2, 64–69. [Google Scholar]
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Figure 1. Effects of abscisic acid on the photosynthetic pigment content of rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Figure 1. Effects of abscisic acid on the photosynthetic pigment content of rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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Figure 2. Effects of abscisic acid on the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) of rice under salt stress in the filling stage. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Figure 2. Effects of abscisic acid on the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci) of rice under salt stress in the filling stage. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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Figure 3. Effects of abscisic acid on antioxidant enzyme activity in rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Figure 3. Effects of abscisic acid on antioxidant enzyme activity in rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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Figure 4. Effects of abscisic acid on oxidative metabolism under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Figure 4. Effects of abscisic acid on oxidative metabolism under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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Figure 5. Effects of abscisic acid on osmotic substances in rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Figure 5. Effects of abscisic acid on osmotic substances in rice under salt stress. CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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Table 1. Effects of abscisic acid on the morphological indices of rice in the filling stage under salt stress.
Table 1. Effects of abscisic acid on the morphological indices of rice in the filling stage under salt stress.
TreatmentPlant Height (cm)Stem Thickness (cm)Leaf Area (cm2)Above-Ground Dry Weight (g)
CK76.10 ± 0.53 a12.03 ± 0.15 ab9774.57 ± 204.01 a3.71 ± 0.19 a
S174.37 ± 0.32 ab11.50 ± 0.20 bc9471.85 ± 286.25 a3.28 ± 0.26 abc
S272.83 ± 0.55 abc11.65 ± 0.05 b8771.23 ± 179.75 a3.47 ± 0.16 ab
NA63.53 ± 2.03 d10.40 ± 0.25 c3199.05 ± 87.25 c1.83 ± 0.27 d
NAS170.13 ± 0.09 c13.03 ± 0.26 ab4480.00 ± 457.17 c2.43 ± 0.13 cd
NAS272.13 ± 1.51 bc13.15 ± 0.95 a5824.20 ± 643.51 b2.79 ± 0.55 bc
Note: CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
Table 2. Effects of abscisic acid on rice yield and rice composition indices under salt stress.
Table 2. Effects of abscisic acid on rice yield and rice composition indices under salt stress.
TreatmentEffective Panicle Number
(Panicle·pot−1)		Number of Primary BranchesNumber of Secondary BranchesNumber of Spikelets
per Panicle
(Spikelet·Panicle−1)		Percentage of Filled Grains
(%)		1000-Grain Weight (g−1)Yield
(g/Plant)
CK12.50 ± 0.50 ab12.00 ± 0.58 ab14.67 ± 0.33 ab137.67 ± 6.49 a66.57 ± 0.01 bc19.05 ± 1.27 bc6.95 ± 0.09 bc
S113.50 ± 1.50 a11.33 ± 0.33 bc18.33 ± 0.67 a141.50 ± 6.50 a74.9 ± 0.06 ab20.81 ± 0.41 ab7.463 ± 0.26 ab
S213.67 ± 1.20 a12.67 ± 0.33 a19.00 ± 3.51 a144.67 ± 4.91 a79.36 ± 0.01 a22.49 ± 0.54 a7.67 ± 0.46 a
NA8.50 ± 1.50 b10.33 ± 0.33 c10.67 ± 0.33 b109.00 ± 0.58 b55.02 ± 0.02 d15.81 ± 0.89 d5.02 ± 0.22 e
NAS19.00 ± 1.15 b10.50 ± 0.50 c12.67 ± 0.88 b119.33 ± 3.67 ab69.35 ± 0.01 cd17.65 ± 0.53 cd5.76 ± 0.20 d
NAS210.00 ± 1.00 ab11.00 ± 0.00 bc14.00 ± 0.58 ab136.00 ± 14.53 a69.66 ± 0.03 bc19.20 ± 0.73 bc6.49 ± 0.10 c
Note: CK (control treatment), S1 ((water, spraying S-ABA in 3-leaf/1-heart stage), S2 ((water, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage), NA (0.4%NaCl), NAS1 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage), NAS2 (0.4%NaCl, spraying S-ABA in 3-leaf/1-heart stage and twice in break stage). Values are the mean ± SD of three replicate samples. Different letters in the data column indicate significant differences (p < 0.05) according to Duncan’s test.
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MDPI and ACS Style

Wang, X.; Ma, G.; Feng, N.; Zheng, D.; Zhou, H.; Li, J.; Wu, J.; Xu, B.; Su, W.; Huang, Y. Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics. Agronomy 2025, 15, 309. https://doi.org/10.3390/agronomy15020309

AMA Style

Wang X, Ma G, Feng N, Zheng D, Zhou H, Li J, Wu J, Xu B, Su W, Huang Y. Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics. Agronomy. 2025; 15(2):309. https://doi.org/10.3390/agronomy15020309

Chicago/Turabian Style

Wang, Xi, Guohui Ma, Naijie Feng, Dianfeng Zheng, Hang Zhou, Jiahuang Li, Jiashuang Wu, Bing Xu, Weiling Su, and Yixi Huang. 2025. "Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics" Agronomy 15, no. 2: 309. https://doi.org/10.3390/agronomy15020309

APA Style

Wang, X., Ma, G., Feng, N., Zheng, D., Zhou, H., Li, J., Wu, J., Xu, B., Su, W., & Huang, Y. (2025). Abscisic Acid Can Improve the Salt Tolerance and Yield of Rice by Improving Its Physiological Characteristics. Agronomy, 15(2), 309. https://doi.org/10.3390/agronomy15020309

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