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20 pages, 1331 KiB

Open AccessArticle

Effects of Water Regime, Genotype, and Formative Stages on the Agro-Physiological Response of Sugarcane (Saccharum officinarum L.) to Drought

by Jose Arnel O. Reyes, Arvin S. Carpentero, Primitivo Jose A. Santos and Evelyn F. Delfin

Plants 2020, 9(5), 661; https://doi.org/10.3390/plants9050661 - 23 May 2020

Cited by 13 | Viewed by 4717

Abstract

Drought during the formative stages of a plant’s growth triggers a sequence of responses to maintain optimal growing conditions, but often at the expense of crop productivity. Two field experiments were conducted to determine the effect of drought on 10 high-yielding sugarcane genotypes [...] Read more.

Drought during the formative stages of a plant’s growth triggers a sequence of responses to maintain optimal growing conditions, but often at the expense of crop productivity. Two field experiments were conducted to determine the effect of drought on 10 high-yielding sugarcane genotypes at two formative stages (the tillering stage (TS) and stalk elongation (SS)), within 30 days after treatment imposition. The experiments followed a split-plot in a randomized complete block design with three replicates per genotype. Agro-physiological responses to drought were observed to compare the differences in the response of sugarcane during the two formative stages. Drought significantly reduced total chlorophyll content (Chl) and stomatal conductance (Gs) for both formative stages, while significantly increasing total scavenging activity (AOA) and electrolyte leakage (EC). A higher level of Chl was observed in the stalk elongation stage compared to the tillering stage; however, lower AOA coupled with higher EC in the stalk elongation stage suggests higher drought susceptibility. Pearson's correlation analysis revealed a stronger correlation between plant height, internode length, Chl, AOA, EC, and Gs at the tillering stage relative to the stalk elongation stage. Moreover, results from the multivariate analysis indicate the different contribution values of each parameter, supplementing the hypothesized difference in response between the two formative stages. Multivariate analysis clustered the 10 genotypes into groups based on the traits evaluated, suggesting the ability of these traits to detect differences in a sample population. The observed relationship among traits during the two formative stages of sugarcane will be significant in screening and identifying drought-susceptible and drought-tolerant genotypes for variety development studies. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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18 pages, 3368 KiB

Open AccessFeature PaperArticle

Characterization of Glutamate-Mediated Hormonal Regulatory Pathway of the Drought Responses in Relation to Proline Metabolism in Brassica napus L.

by Van Hien La, Bok-Rye Lee, Md. Tabibul Islam, Md. Al Mamun, Sang-Hyun Park, Dong-Won Bae and Tae-Hwan Kim

Plants 2020, 9(4), 512; https://doi.org/10.3390/plants9040512 - 16 Apr 2020

Cited by 31 | Viewed by 4977

Abstract

Proline metabolism influences the metabolic and/or signaling pathway in regulating plant stress responses. This study aimed to characterize the physiological significance of glutamate (Glu)-mediated proline metabolism in the drought stress responses, focusing on the hormonal regulatory pathway. The responses of cytosolic Ca²⁺ [...] Read more.

Proline metabolism influences the metabolic and/or signaling pathway in regulating plant stress responses. This study aimed to characterize the physiological significance of glutamate (Glu)-mediated proline metabolism in the drought stress responses, focusing on the hormonal regulatory pathway. The responses of cytosolic Ca²⁺ signaling, proline metabolism, and redox components to the exogenous application of Glu in well-watered or drought-stressed plants were interpreted in relation to endogenous hormone status and their signaling genes. Drought-enhanced level of abscisic acid (ABA) was concomitant with the accumulation of ROS and proline, as well as loss of reducing potential, which was assessed by measuring NAD(P)H/NAD(P)⁺ and GSH/GSSG ratios. Glu application to drought-stressed plants increased both salicylic acid (SA) and cytosolic Ca²⁺ levels, with the highest expression of calcium-dependent protein kinase (CPK5) and salicylic acid synthesis-related ICS1. The SA-enhanced CPK5 expression was closely associated with further enhancement of proline synthesis-related genes (P5CS1, P5CS2, and P5CR) expression and a reset of reducing potential with enhanced expression of redox regulating genes (TRXh5 and GRXC9) in a SA-mediated NPR1- and/or PR1-dependent manner. These results clearly indicate that Glu-activated interplay between SA- and CPK5-signaling as well as Glu-enhanced proline synthesis are crucial in the amelioration of drought stress in Brassica napus. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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17 pages, 2926 KiB

Open AccessArticle

Transcriptomic Response to Water Deficit Reveals a Crucial Role of Phosphate Acquisition in a Drought-Tolerant Common Bean Landrace

by Cristina María López, Manuel Pineda and Josefa M Alamillo

Plants 2020, 9(4), 445; https://doi.org/10.3390/plants9040445 - 2 Apr 2020

Cited by 9 | Viewed by 3678

Abstract

Drought is one of the most critical factors limiting legume crop productivity. Understanding the molecular mechanisms of drought tolerance in the common bean is required to improve the yields of this important crop under adverse conditions. In this work, RNA-seq analysis was performed [...] Read more.

Drought is one of the most critical factors limiting legume crop productivity. Understanding the molecular mechanisms of drought tolerance in the common bean is required to improve the yields of this important crop under adverse conditions. In this work, RNA-seq analysis was performed to compare the transcriptome profiles of drought-stressed and well-irrigated plants of a previously characterized drought-tolerant common bean landrace. The analysis revealed responses related with the abscisic acid signaling, including downregulation of a phosphatase 2C (PP2C) and an abscisic acid-8′ hydroxylase, and upregulation of several key transcription factors and genes involved in cell wall remodeling, synthesis of osmoprotectants, protection of photosynthetic apparatus, and downregulation of genes involved in cell expansion. The results also highlighted a significant proportion of differentially expressed genes related to phosphate starvation response. In addition, the moderate detrimental effects of drought in the biomass of these tolerant plants were abolished by the addition of phosphate, thus indicating that, besides the ABA-mediated response, acquisition of phosphate could be crucial for the drought tolerance of this common bean genotype. These results provided information about the mechanisms involved in drought response of common bean response that could be useful for enhancing the drought tolerance of this important crop legume. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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19 pages, 1779 KiB

Open AccessArticle

Foliar Pre-Treatment with Abscisic Acid Enhances Olive Tree Drought Adaptability

by Cátia Brito, Lia-Tânia Dinis, Helena Ferreira, José Moutinho-Pereira and Carlos M. Correia

Plants 2020, 9(3), 341; https://doi.org/10.3390/plants9030341 - 8 Mar 2020

Cited by 13 | Viewed by 3647

Abstract

Water is the most widely limiting factor for plants distribution, survival and agricultural productivity, their responses to drought and recovery being critical for their success and productivity. Olea europaea L. is a well-adapted species to cyclic drought events, still at considerable expense of [...] Read more.

Water is the most widely limiting factor for plants distribution, survival and agricultural productivity, their responses to drought and recovery being critical for their success and productivity. Olea europaea L. is a well-adapted species to cyclic drought events, still at considerable expense of carbon reserves and CO₂ supply. To study the role of abscisic acid (ABA) as a promoter of drought adaptability, young potted olive trees subjected to three drought-recovery cycles were pre-treated with ABA. The results demonstrated that ABA pre-treatment allowed the delay of the drought effects on stomatal conductance (g_s) and net photosynthesis (A_n), and under severe drought, permitted the reduction of the non-stomatal limitations to A_n and the relative water content decline, the accumulation of compatible solutes and avoid the decline of photosynthetic pigments, soluble proteins and total thiols concentrations and the accumulation of ROS. Upon rewatering, ABA-sprayed plants showed an early recovery of A_n. The plant ionome was also changed by the addition of ABA, with special influence on root K, N and B concentrations. The improved physiological and biochemical functions of the ABA-treated plants attenuated the drought-induced decline in biomass accumulation and potentiated root growth and whole-plant water use efficiency after successive drought-rewatering cycles. These changes are likely to be of real adaptive significance, with important implications for olive tree growth and productivity. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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12 pages, 6520 KiB

Open AccessArticle

Characterization of Trehalose-6-phosphate Synthase and Trehalose-6-phosphate Phosphatase Genes and Analysis of its Differential Expression in Maize (Zea mays) Seedlings under Drought Stress

by Phamela Acosta-Pérez, Bianka Dianey Camacho-Zamora, Edward A. Espinoza-Sánchez, Guadalupe Gutiérrez-Soto, Francisco Zavala-García, María Jazmín Abraham-Juárez and Sugey Ramona Sinagawa-García

Plants 2020, 9(3), 315; https://doi.org/10.3390/plants9030315 - 3 Mar 2020

Cited by 23 | Viewed by 4891

Abstract

Maize is the most important crop around the world and it is highly sensitive to abiotic stress caused by drought, excessive salinity, and extreme temperature. In plants, trehalose has been widely studied for its role in plant adaptation to different abiotic stresses such [...] Read more.

Maize is the most important crop around the world and it is highly sensitive to abiotic stress caused by drought, excessive salinity, and extreme temperature. In plants, trehalose has been widely studied for its role in plant adaptation to different abiotic stresses such as drought, high and low temperature, and osmotic stress. Thus, the aim of this work was to clone and characterize at molecular level the trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP) genes from maize and to evaluate its differential expression in maize seedlings under drought stress. To carry out this, resistant and susceptible maize lines were subjected to drought stress during 72 h. Two full-length cDNAs of TPS and one of TPP were cloned and sequenced. Then, TPS and TPP amino acid sequences were aligned with their homologs from different species, showing highly conserved domains and the same catalytic sites. Relative expression of both genes was evaluated by RT-qPCR at different time points. The expression pattern showed significant induction after 0.5 h in resistant lines and after two to four hours in susceptible plants, showing their participation in drought stress response. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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24 pages, 1290 KiB

Open AccessArticle

Use of Nitric Oxide and Hydrogen Peroxide for Better Yield of Wheat (Triticum aestivum L.) under Water Deficit Conditions: Growth, Osmoregulation, and Antioxidative Defense Mechanism

by Noman Habib, Qasim Ali, Shafaqat Ali, Muhammad Tariq Javed, Muhammad Zulqurnain Haider, Rashida Perveen, Muhammad Rizwan Shahid, Muhammad Rizwan, Mohamed M. Abdel-Daim, Amr Elkelish and May Bin-Jumah

Plants 2020, 9(2), 285; https://doi.org/10.3390/plants9020285 - 22 Feb 2020

Cited by 122 | Viewed by 7333

Abstract

The present experiment was carried out to study the influences of exogenously-applied nitric oxide (NO) donor sodium nitroprusside (SNP) and hydrogen peroxide (H₂O₂) as seed primers on growth and yield in relation with different physio-biochemical parameters, antioxidant activities, and [...] Read more.

The present experiment was carried out to study the influences of exogenously-applied nitric oxide (NO) donor sodium nitroprusside (SNP) and hydrogen peroxide (H₂O₂) as seed primers on growth and yield in relation with different physio-biochemical parameters, antioxidant activities, and osmolyte accumulation in wheat plants grown under control (100% field capacity) and water stress (60% field capacity) conditions. During soaking, the seeds were covered and kept in completely dark. Drought stress markedly reduced the plant growth, grain yield, leaf photosynthetic pigments, total phenolic content (TPC), total soluble proteins (TSP), leaf water potential (Ψ_w), leaf turgor potential (Ψ_p), osmotic potential (Ψ_s), and leaf relative water content (LRWC), while it increased the activities of enzymatic antioxidants and the accumulation of leaf ascorbic acid (AsA), proline (Pro), glycine betaine (GB), malondialdehyde (MDA), and H₂O₂. However, seed priming with SNP and H₂O₂ alone and in combination mitigated the deleterious effects of water stress on growth and yield by improving the Ψ_w, Ψ_s, Ψ_p, photosynthetic pigments, osmolytes accumulation (GB and Pro), TSP, and the antioxidative defense mechanism. Furthermore, the application of NO and H₂O₂ as seed primers also reduced the accumulation of H₂O₂ and MDA contents. The effectiveness was treatment-specific and the combined application was also found to be effective. The results revealed that exogenous application of NO and H₂O₂ was effective in increasing the tolerance of wheat plants under drought stress in terms of growth and grain yield by regulating plant–water relations, the antioxidative defense mechanism, and accumulation of osmolytes, and by reducing the membrane lipid peroxidation. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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17 pages, 1670 KiB

Open AccessArticle

Elucidating the Possible Involvement of Maize Aquaporins and Arbuscular Mycorrhizal Symbiosis in the Plant Ammonium and Urea Transport under Drought Stress Conditions

by Gabriela Quiroga, Gorka Erice, Ricardo Aroca, Antonio Delgado-Huertas and Juan Manuel Ruiz-Lozano

Plants 2020, 9(2), 148; https://doi.org/10.3390/plants9020148 - 23 Jan 2020

Cited by 24 | Viewed by 3199

Abstract

This study investigates the possible involvement of maize aquaporins which are regulated by arbuscular mycorrhizae (AM) in the transport in planta of ammonium and/or urea under well-watered and drought stress conditions. The study also aims to better understand the implication of the AM [...] Read more.

This study investigates the possible involvement of maize aquaporins which are regulated by arbuscular mycorrhizae (AM) in the transport in planta of ammonium and/or urea under well-watered and drought stress conditions. The study also aims to better understand the implication of the AM symbiosis in the uptake of urea and ammonium and its effect on plant physiology and performance under drought stress conditions. AM and non-AM maize plants were cultivated under three levels of urea or ammonium fertilization (0, 3 µM or 10 mM) and subjected or not to drought stress. Plant aquaporins and physiological responses to these treatments were analyzed. AM increased plant biomass in absence of N fertilization or under low urea/ ammonium fertilization, but no effect of the AM symbiosis was observed under high N supply. This effect was associated with reduced oxidative damage to lipids and increased N accumulation in plant tissues. High N fertilization with either ammonium or urea enhanced net photosynthesis (A_N) and stomatal conductance (gs) in plants maintained under well-watered conditions, but 14 days after drought stress imposition these parameters declined in AM plants fertilized with high N doses. The aquaporin ZmTIP1;1 was up-regulated by both urea and ammonium and could be transporting these two N forms in planta. The differential regulation of ZmTIP4;1 and ZmPIP2;4 with urea fertilization and of ZmPIP2;4 with NH₄⁺ supply suggests that these two aquaporins may also play a role in N mobilization in planta. At the same time, these aquaporins were also differentially regulated by the AM symbiosis, suggesting a possible role in the AM-mediated plant N homeostasis that deserves future studies. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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15 pages, 1324 KiB

Open AccessArticle

Exogenously Applied Ascorbic Acid-Mediated Changes in Osmoprotection and Oxidative Defense System Enhanced Water Stress Tolerance in Different Cultivars of Safflower (Carthamus tinctorious L.)

by Ayesha Farooq, Shazia Anwer Bukhari, Nudrat A. Akram, Muhammad Ashraf, Leonard Wijaya, Mohammed Nasser Alyemeni and Parvaiz Ahmad

Plants 2020, 9(1), 104; https://doi.org/10.3390/plants9010104 - 14 Jan 2020

Cited by 105 | Viewed by 5798

Abstract

The present study was conducted to examine the effect of exogenously applied ascorbic acid (AsA) on osmoprotectants and the oxidative defense system in four cultivars (16171, 16183, 16207 and 16246) of safflower under well-watered and water deficit conditions. Water stress (60% field capacity) [...] Read more.

The present study was conducted to examine the effect of exogenously applied ascorbic acid (AsA) on osmoprotectants and the oxidative defense system in four cultivars (16171, 16183, 16207 and 16246) of safflower under well-watered and water deficit conditions. Water stress (60% field capacity) significantly decreased the shoot and root fresh and dry weights, shoot and root lengths and chlorophyll contents in all four safflower cultivars, while it increased the leaf free proline, total phenolics, total soluble proteins, hydrogen peroxide content and activities of catalase, superoxide dismutase and peroxidase enzymes. Foliar-applied (100 mg L⁻¹ and 150 mg L⁻¹) ascorbic acid caused a marked improvement in shoot and root fresh and dry weights, plant height, chlorophyll and AsA contents as well as the activity of peroxidase (POD) enzyme particularly under water deficit conditions. It also increased the accumulation of leaf proline, total phenolics, total soluble proteins and glycine betaine (GB) content in all four cultivars. Exogenously applied AsA lowered the contents of MDA and H₂O_2, and the activities of CAT and SOD enzymes. Overall, exogenously applied AsA had a positive effect on the growth of safflower plants under water deficit conditions which could be related to AsA-induced enhanced osmoprotection and regulation of antioxidant defense system. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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11 pages, 559 KiB

Open AccessArticle

Potassium Application Improves Grain Yield and Alleviates Drought Susceptibility in Diverse Maize Hybrids

by Sami Ul-Allah, Muhammad Ijaz, Ahmad Nawaz, Abdul Sattar, Ahmad Sher, Muhammad Naeem, Umbreen Shahzad, Umar Farooq, Farukh Nawaz and Khalid Mahmood

Plants 2020, 9(1), 75; https://doi.org/10.3390/plants9010075 - 7 Jan 2020

Cited by 54 | Viewed by 6587

Abstract

Maize (Zea mays L.) is an important component of global food security but its production is threatened by abiotic stresses in climate change scenarios, especially drought stress. Many multinational companies have introduced maize hybrids worldwide which have variable performance under diverse environmental [...] Read more.

Maize (Zea mays L.) is an important component of global food security but its production is threatened by abiotic stresses in climate change scenarios, especially drought stress. Many multinational companies have introduced maize hybrids worldwide which have variable performance under diverse environmental conditions. The maize production is likely to be affected by a future water crisis. Potassium (K) is a well-known macronutrient which improves the performance of cereals under abiotic stresses. In this field experiment, we assessed the influence of soil applied K on the productivity of diverse maize hybrids grown under well-watered and drought stress conditions. The study consisted of three K levels viz., control (no KCl), KCl at 50 kg ha⁻¹, and KCI at 75 kg ha⁻¹ factorally combined with two irrigation levels (i.e., normal recommended irrigation, well-watered condition, and half of the recommended irrigation, drought stress condition) and eight maize hybrids. Irrigation was kept in main plots, potassium in subplot, and maize hybrids in sub-subplots. The results revealed that performance of the maize hybrids was significantly influenced by all three factors, and the interaction of irrigation with potassium and irrigation with hybrids was significant; results being non-significant for all other interactions. Potassium application improved yield traits and water productivity under both normal and water stress conditions but effect was more prominent under water stress conditions than normal conditions. Potassium application also alleviated drought susceptibility of all maize hybrids. In all cases, the performance of maize hybrids was maximum under potassium application at 75 kg ha⁻¹. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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20 pages, 2804 KiB

Open AccessArticle

Improved Drought Tolerance by AMF Inoculation in Maize (Zea mays) Involves Physiological and Biochemical Implications

by Naheeda Begum, Muhammad Abass Ahanger, Yunyun Su, Yafang Lei, Nabil Sabet A. Mustafa, Parvaiz Ahmad and Lixin Zhang

Plants 2019, 8(12), 579; https://doi.org/10.3390/plants8120579 - 6 Dec 2019

Cited by 200 | Viewed by 8992

Abstract

The role of arbuscular mycorrhizal fungus (AMF, Glomus versiforme) in amelioration of drought-induced effects on growth and physio-biochemical attributes in maize (Zea mays L.) was studied. Maize plants were exposed to two drought regimes, i.e., moderate drought (MD) and severe drought [...] Read more.

The role of arbuscular mycorrhizal fungus (AMF, Glomus versiforme) in amelioration of drought-induced effects on growth and physio-biochemical attributes in maize (Zea mays L.) was studied. Maize plants were exposed to two drought regimes, i.e., moderate drought (MD) and severe drought (SD), with and without AMF inoculation. Drought at both levels reduced plant height, and chlorophyll and carotenoid content, thereby impeding photosynthesis. In addition, drought stress enhanced the generation of toxic reactive oxygen species (ROS), including H₂O₂, resulting in membrane damage reflected as increased electrolyte leakage and lipid peroxidation. Such negative effects were much more apparent under SD conditions that those of MD and the control, however, AMF inoculation significantly ameliorated the deleterious effects of drought-induced oxidative damage. Under control conditions, inoculation of AMF increased growth and photosynthesis by significantly improving chlorophyll content, mineral uptake and assimilation. AMF inoculation increased the content of compatible solutes, such as proline, sugars and free amino acids, assisting in maintaining the relative water content. Up-regulation of the antioxidant system was obvious in AMF-inoculated plants, thereby mediating quick alleviation of oxidative effects of drought through elimination of ROS. In addition, AMF mediated up-regulation of the antioxidant system contributed to maintenance of redox homeostasis, leading to protection of major metabolic pathways, including photosynthesis, as observed in the present study. Total phenols increased due to AMF inoculation under both MD and SD conditions. The present study advocates the beneficial role of G. versiforme inoculation in maize against drought stress. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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21 pages, 2543 KiB

Open AccessArticle

Qualitative and Quantitative Differences in Osmolytes Accumulation and Antioxidant Activities in Response to Water Deficit in Four Mediterranean Limonium Species

by Sara González-Orenga, Mohamad Al Hassan, Josep V. Llinares, Purificación Lisón, M. Pilar López-Gresa, Mercedes Verdeguer, Oscar Vicente and Monica Boscaiu

Plants 2019, 8(11), 506; https://doi.org/10.3390/plants8110506 - 15 Nov 2019

Cited by 18 | Viewed by 3927

Abstract

Limonium is a genus represented in the Iberian Peninsula by numerous halophytic species that are affected in nature by salinity, and often by prolonged drought episodes. Responses to water deficit have been studied in four Mediterranean Limonium species, previously investigated regarding salt tolerance [...] Read more.

Limonium is a genus represented in the Iberian Peninsula by numerous halophytic species that are affected in nature by salinity, and often by prolonged drought episodes. Responses to water deficit have been studied in four Mediterranean Limonium species, previously investigated regarding salt tolerance mechanisms. The levels of biochemical markers, associated with specific responses—photosynthetic pigments, mono- and divalent ions, osmolytes, antioxidant compounds and enzymes—were determined in the control and water-stressed plants, and correlated with their relative degree of stress-induced growth inhibition. All the tested Limonium taxa are relatively resistant to drought on the basis of both the constitutive presence of high leaf ion levels that contribute to osmotic adjustment, and the stress-induced accumulation of osmolytes and increased activity of antioxidant enzymes, albeit with different qualitative and quantitative induction patterns. Limonium santapolense activated the strongest responses and clearly differed from Limonium virgatum, Limonium girardianum, and Limonium narbonense, as indicated by cluster and principal component analysis (PCA) analyses in agreement with its drier natural habitat, and compared to that of the other plants. Somewhat surprisingly, however, L. santapolense was the species most affected by water deficit in growth inhibition terms, which suggests the existence of additional mechanisms of defense operating in the field that cannot be mimicked in greenhouses. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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16 pages, 2771 KiB

Open AccessArticle

Effect of Wheat Straw as a Cover Crop on the Chlorophyll, Seed, and Oilseed Yield of Trigonella foeunm graecum L under Water Deficiency and Weed Competition

by Nabil Raheem Lahmod, Jawadayn Talib Alkooranee, Ahmed Abed Gatea Alshammary and Jesús Rodrigo-Comino

Plants 2019, 8(11), 503; https://doi.org/10.3390/plants8110503 - 14 Nov 2019

Cited by 9 | Viewed by 4647

Abstract

The effects of water stress on fenugreek crops are well documented. However, little is known about how these plants respond to water deficits under a soil-mulching system when the surface is protected. Therefore, the current research aims to demonstrate the possibility of reducing [...] Read more.

The effects of water stress on fenugreek crops are well documented. However, little is known about how these plants respond to water deficits under a soil-mulching system when the surface is protected. Therefore, the current research aims to demonstrate the possibility of reducing the impact of water stress and weed competition on the fenugreek crop through the use of wheat residues as a cover crop on the soil surface. A field experiment was carried out during the winter season (2016–2017) using a split-plot design arrangement with three replicates. The experiments included four levels of water deficit, which consisted of a 40% depletion treatment as a control plot, and 50%, 60%, and 70% depletion from the field capacity (DFC) for the other studied fields. The subplot division consisted of mulching the soil with wheat residues. The results demonstrated that soil-mulching systems and a water deficit are able to impact the fenugreek yield of seed and oil. Additionally, soil mulching led to a decrease in weed density and biomass, chlorophyll content, and biological yield. Although high water deficit (70% DFC) led to yield and growth reduction, the use of wheat residue as a cover crop moderated the effect of a strong water deficit on plants and showed clear reduction of weed growth. Therefore, the results suggest that soil mulching can mitigate the adverse effects of water deficit by conserving soil moisture and decreasing weeds, which can be considered an acclimation mechanism under water-deficit conditions to avoid yield loss. Moreover, the allelopathic effects of wheat residue were observed on fenugreek crops subjected to irrigation after depleting 40% soil water moisture, but these effects disappeared within 90 days of sowing. We conclude that these results can help future agricultural planning and systems in order to increase productivity, reduce irrigation costs, and conserve soil quality. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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14 pages, 1713 KiB

Open AccessArticle

Silicon Priming Regulates Morpho-Physiological Growth and Oxidative Metabolism in Maize under Drought Stress

by Abida Parveen, Wei Liu, Saddam Hussain, Jaleel Asghar, Shagufta Perveen and Yousheng Xiong

Plants 2019, 8(10), 431; https://doi.org/10.3390/plants8100431 - 20 Oct 2019

Cited by 139 | Viewed by 7211

Abstract

Seed priming with silicon (Si) is an efficient and easy method to regulate plant tolerance against different abiotic stresses. A pot experiment was conducted to examine the Si-mediated changes in oxidative defense and some vital physio-biochemical parameters of maize under a limited water [...] Read more.

Seed priming with silicon (Si) is an efficient and easy method to regulate plant tolerance against different abiotic stresses. A pot experiment was conducted to examine the Si-mediated changes in oxidative defense and some vital physio-biochemical parameters of maize under a limited water supply. For this purpose, two maize varieties (Pearl and Malka) with different Si priming treatments (0, 4 mM, 6 mM) were grown under a control and 60% field capacity for three weeks. At 60% field capacity, significant reductions in plant growth attributes and chlorophyll contents were recorded compared with the control. The negative effects of drought stress were more severe for Malka compared with Pearl. Drought stress increased the malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) contents, altered the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), and triggered the accumulation of soluble sugars, glycine betaine, proline, and phenolics contents. Nevertheless, seed priming with silicon at 4 or 6 mM was effective in alleviating the detrimental effects of drought stress in both cultivars. Si priming particularly at 6 mM significantly enhanced the shoot and root lengths as well as their biomass and improved the levels of photosynthetic pigments. Moreover, Si treatments enhanced the activities of antioxidant enzymes (SOD, POD, and CAT) while it reduced the MDA and H₂O₂ contents in both cultivars under stress conditions. In crux, the present investigation suggests that Si priming mitigates the harmful effects of drought stress and contributes to the recovery of maize growth. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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28 pages, 5107 KiB

Open AccessArticle

Identification of Factors Linked to Higher Water-Deficit Stress Tolerance in Amaranthus hypochondriacus Compared to Other Grain Amaranths and A. hybridus, Their Shared Ancestor

by Tzitziki González-Rodríguez, Ismael Cisneros-Hernández, Jonathan Acosta Bayona, Enrique Ramírez-Chavez, Norma Martínez-Gallardo, Erika Mellado-Mojica, Mercedes G. López-Pérez, Jorge Molina-Torres and John Délano-Frier

Plants 2019, 8(7), 239; https://doi.org/10.3390/plants8070239 - 22 Jul 2019

Cited by 10 | Viewed by 4626

Abstract

Water deficit stress (WDS)-tolerance in grain amaranths (Amaranthus hypochondriacus, A. cruentus and A. caudatus), and A. hybridus, their presumed shared ancestor, was examined. A. hypochondriacus was the most WDS-tolerant species, a trait that correlated with an enhanced osmotic adjustment [...] Read more.

Water deficit stress (WDS)-tolerance in grain amaranths (Amaranthus hypochondriacus, A. cruentus and A. caudatus), and A. hybridus, their presumed shared ancestor, was examined. A. hypochondriacus was the most WDS-tolerant species, a trait that correlated with an enhanced osmotic adjustment (OA), a stronger expression of abscisic acid (ABA) marker genes and a more robust sugar starvation response (SSR). Superior OA was supported by higher basal hexose (Hex) levels and high Hex/sucrose (Suc) ratios in A. hypochondriacus roots, which were further increased during WDS. This coincided with increased invertase, amylase and sucrose synthase activities and a strong depletion of the starch reserves in leaves and roots. The OA was complemented by the higher accumulation of proline, raffinose, and other probable raffinose-family oligosaccharides of unknown structure in leaves and/or roots. The latter coincided with a stronger expression of Galactinol synthase 1 and Raffinose synthase in leaves. Increased SnRK1 activity and expression levels of the class II AhTPS9 and AhTPS11 trehalose phosphate synthase genes, recognized as part of the SSR network in Arabidopsis, were induced in roots of stressed A. hypochondriacus. It is concluded that these physiological modifications improved WDS in A. hypochondriacus by raising its water use efficiency. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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Review

Jump to: Research

18 pages, 1381 KiB

Open AccessReview

The Mode of Cytokinin Functions Assisting Plant Adaptations to Osmotic Stresses

by Ranjit Singh Gujjar and Kanyaratt Supaibulwatana

Plants 2019, 8(12), 542; https://doi.org/10.3390/plants8120542 - 26 Nov 2019

Cited by 40 | Viewed by 6368

Abstract

Plants respond to abiotic stresses by activating a specific genetic program that supports survival by developing robust adaptive mechanisms. This leads to accelerated senescence and reduced growth, resulting in negative agro-economic impacts on crop productivity. Cytokinins (CKs) customarily regulate various biological processes in [...] Read more.

Plants respond to abiotic stresses by activating a specific genetic program that supports survival by developing robust adaptive mechanisms. This leads to accelerated senescence and reduced growth, resulting in negative agro-economic impacts on crop productivity. Cytokinins (CKs) customarily regulate various biological processes in plants, including growth and development. In recent years, cytokinins have been implicated in adaptations to osmotic stresses with improved plant growth and yield. Endogenous CK content under osmotic stresses can be enhanced either by transforming plants with a bacterial isopentenyl transferase (IPT) gene under the control of a stress inducible promoter or by exogenous application of synthetic CKs. CKs counteract osmotic stress-induced premature senescence by redistributing soluble sugars and inhibiting the expression of senescence-associated genes. Elevated CK contents under osmotic stress antagonize abscisic acid (ABA) signaling and ABA mediated responses, delay leaf senescence, reduce reactive oxygen species (ROS) damage and lipid peroxidation, improve plant growth, and ameliorate osmotic stress adaptability in plants. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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17 pages, 2014 KiB

Open AccessEditor’s ChoiceReview

Melatonin Mediated Regulation of Drought Stress: Physiological and Molecular Aspects

by Anket Sharma and Bingsong Zheng

Plants 2019, 8(7), 190; https://doi.org/10.3390/plants8070190 - 26 Jun 2019

Cited by 167 | Viewed by 10538

Abstract

Drought stress adversely effects physiological and biochemical processes of plants, leading to a reduction in plant productivity. Plants try to protect themselves via activation of their internal defense system, but severe drought causes dysfunction of this defense system. The imbalance between generation and [...] Read more.

Drought stress adversely effects physiological and biochemical processes of plants, leading to a reduction in plant productivity. Plants try to protect themselves via activation of their internal defense system, but severe drought causes dysfunction of this defense system. The imbalance between generation and scavenging of reactive oxygen species (ROS) leads to oxidative stress. Melatonin, a multifunctional molecule, has the potential to protect plants from the adverse effects of drought stress by enhancing the ROS scavenging efficiency. It helps in protection of photosynthetic apparatus and reduction of drought induced oxidative stress. Melatonin regulates plant processes at a molecular level, which results in providing better resistance against drought stress. In this review, the authors have discussed various physiological and molecular aspects regulated by melatonin in plants under drought conditions, along with their underlying mechanisms. Full article

(This article belongs to the Special Issue Plant Responses to Water-Deficit Stress)

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