Effects of Temperature Fluctuations on the Growth Cycle of Rice

Abstract

Temperature is a critical environmental factor affecting the growth and development of rice, especially under the backdrop of global climate change, where temperature fluctuations have become increasingly significant in influencing the growth cycle and development rate of rice. To comprehensively assess the impact of temperature variations on the different growth stages of rice, this study integrates data from multiple relevant studies published between 1980 and 2024. By selecting research focused on the influence of temperature changes on the rice development cycle, a meta-analysis is conducted to systematically evaluate the effects of temperature on the growth rates of rice during its six key developmental stages. The results indicate that increased temperatures significantly accelerate the development rate of rice during all growth stages, with a general acceleration in growth speed at different developmental phases. The study further found that when the temperature ranges from 28 °C to 32 °C, the growing conditions for rice are most favorable, exhibiting the optimal development rate. This study provides scientific evidence for understanding how temperature changes affect rice growth and development and offers valuable references for rice cultivation management and climate adaptation strategies.

1. Introduction

With the intensification of global climate change, temperature fluctuations have become one of the key factors affecting agricultural production [1]. Temperature changes have profound effects on crop growth, development, yield, and quality, and particularly for rice, an essential staple crop, temperature plays a critical role throughout its entire growth cycle [2]. The growth and development process of rice is a complex biological process that is generally divided into several stages, including germination, tillering, heading, jointing, grain filling, and maturation [3]. The growth rate at each stage is influenced by various environmental factors, with temperature being one of the most significant factors affecting rice growth.

Existing studies have shown that temperature significantly affects rice growth [4]. For example, during the tillering stage, appropriate temperatures help increase the number of tillers and enhance the tillering ability of rice [5]. In the flowering and grain filling stages, high temperatures may lead to heat stress responses in rice, affecting pollen germination and fertilization, thus influencing the final yield [6]. Moreover, both excessively high and low temperatures can affect the growth rate of rice, causing uneven growth or even developmental stagnation [7]. Elevated temperatures not only accelerate the growth rate but may also alter the growth pattern of rice, thus impacting its overall growth performance.

However, most existing studies are based on single experiments or localized investigations, and the results vary significantly due to regional and environmental differences. The experimental design, temperature treatments, and varietal differences used in different studies lead to inconsistent conclusions regarding the impact of temperature changes on rice development. Some studies suggest that moderate temperature increases help enhance the growth rate of rice [8], while others indicate that excessively high temperatures negatively affect rice development, particularly in the later stages of growth, where high temperatures may cause premature maturation, thus affecting yield and quality [9]. This complex interplay of effects makes important to investigate the specific impacts of temperature on rice growth at different stages.

Meta-analysis, as an effective method of comprehensive analysis, overcomes the limitations of single-study conclusions by integrating experimental data from various studies, providing a more comprehensive and accurate perspective [10]. Meta-analysis has been widely used in agricultural research, particularly in studying the impact of climate change on crop growth, and it helps researchers more precisely reveal the cumulative effects of temperature changes on the various growth stages of crops [11,12]. However, systematic evaluations of the impact of temperature changes on rice growth across different stages are still limited, and most existing meta-analyses focus on specific growth stages or regions. Therefore, conducting a meta-analysis based on global data from various climatic conditions to systematically explore the impact of temperature changes on the six major growth cycles of rice holds significant theoretical and practical value.

The primary objective of this study is to systematically assess the impact of temperature changes on the development rate across the six growth cycles of rice by integrating existing literature data. The aim of the study is to explore the accelerating effects of temperature rise on the developmental speed of rice at each growth stage and to reveal the influence of different temperature ranges on the optimal growing conditions for rice. Specifically, we will use meta-analysis to examine how temperature rise accelerates the development rate of critical growth cycles such as tillering, jointing, grain filling, and maturation in rice, and identify the optimal temperature range for rice growth under different temperature conditions. In addition, the study will provide data support for future rice cultivation management strategies in the context of climate change, especially in terms of the potential impacts of temperature changes on yield and quality, offering essential theoretical guidance and practical directions for the development of agricultural climate adaptation strategies.

2. Materials and Methods

2.1. Data Sources and Literature Selection

A systematic search and selection of relevant literature was conducted in this study, focusing on research examining the impact of temperature changes on rice growth and development. Multiple academic databases, such as Google Scholar, Web of Science, and CNKI, were used to retrieve studies published between 1980 and 2024. The inclusion criteria were as follows: (1) The study subjects were rice; (2) Temperature change was applied as the independent variable in the experiment; (3) The data included growth rate measurements or metrics related to temperature variations for various growth stages. All studies that met these criteria were included in this meta-analysis.

2.2. Data Extraction

The following key information was extracted from the selected studies: experimental design, sample size, temperature treatment range, and the growth rates of rice at various stages (including germination, tillering, heading, jointing, grain filling, and maturation) under different temperatures. When necessary statistical information, such as standard deviations or sample sizes, was not directly provided in the studies, data were extracted from charts using graphic data extraction tools (e.g., WebPlotDigitizer). For multivariable experiments or data from multiple treatments, different treatment results were treated as independent effect values.

2.3. Meta-Analysis

To systematically evaluate the impact of temperature changes on the development rate of rice at various growth stages, meta-analysis was performed using the metafor package in R (version 4.1.0) [13]. The effect sizes reported in different studies (e.g., standardized mean differences or effect size estimates) were first calculated, and these were weighted using their corresponding standard errors. Due to the substantial heterogeneity among studies, a random-effects model was adopted to integrate the results and better account for inter-study variability [14]. In this analysis, temperature fluctuations were treated as the independent variable, and the developmental durations of rice at different growth stages were treated as the dependent variable. The effect size was measured using the Log Response Ratio (LRR) [15], which represents the difference in growth rates between the temperature treatment and control groups. The statistical significance was tested using 95% confidence intervals [16].

To evaluate the effects of different temperature ranges on the growth stages of rice, subgroup analysis was conducted for the experimental results. The initial step in the analysis involved assessing whether temperature changes significantly affected rice growth and development [17]. For this purpose, the effect sizes between temperature changes and growth rates at various stages were calculated, and heterogeneity tests (e.g., I² statistics) were used to evaluate the variability among studies. When high heterogeneity was observed, potential sources of variability were further analyzed to determine the factors influencing the results. The inter-study heterogeneity was assessed using Q statistics and the I² index, with the I² value reflecting the degree of heterogeneity [18]. Higher I² values indicated greater variability among studies. Heterogeneity was statistically tested using a weighted sum of squares distributed across k − 1 degrees of freedom.

The significance of effect sizes was interpreted using their 95% confidence intervals: when the 95% confidence interval included 0, it indicated no significant difference between the experimental and control groups, suggesting comparable effects on the study subject (p > 0.05). When the 95% confidence interval values were all >0, it indicated that the effect size of the experimental group was significantly greater than that of the control group (p < 0.05). Conversely, when the 95% confidence interval values were all <0, it indicated that the effect size of the experimental group was significantly lower than that of the control group (p < 0.05).

2.4. Subgroup Analysis and Mixed-Effects Model

To further explore the impact of temperature changes on different growth stages, the six major growth cycles of rice (germination, tillering, heading, jointing, grain filling, and maturation) were treated as subgroups for analysis. By analyzing each growth stage separately, the specific effects of temperature changes on the developmental rate at each stage could be determined, thus revealing the mechanisms by which temperature affects each stage. To further improve the accuracy of the model and account for the heterogeneity among studies, a mixed-effects model was also employed to investigate the optimal developmental temperature for each growth cycle [19]. The mixed-effects model allows for the consideration of both fixed and random effects, enabling the evaluation of how different factors influence the temperature effect, leading to a more precise developmental temperature response for each growth stage.

2.5. Response Curve Fitting and Analysis

Building on the results of the mixed-effects model, this study further analyzed the impact of temperature changes on the different growth stages of rice by fitting response curves. We employed a nonlinear regression model to examine the relationship between the developmental rate and temperature at each growth stage, revealing the degree to which temperature conditions affect rice growth. During the fitting process, we used the nlme package in R, which is well suited to handling complex nonlinear relationships, ensuring the accuracy of the temperature–development rate curves [20]. By analyzing the response curves for each growth stage and their correspondence with the mixed-effects model results, we identified the optimal temperature ranges for rice development across different growth cycles under varying temperature conditions.

2.6. Sensitivity Analysis and Statistical Testing

To verify the robustness of the research results, we also conducted a sensitivity analysis. By sequentially excluding specific studies, we recalculated the effect sizes and response curves to determine whether any particular study had a significant impact on the overall results. In addition, we used funnel plot analysis, radar plot testing, and fail-safe N analysis to evaluate the goodness of fit of the model and to assess the potential presence of publication bias [21].

3. Results

3.1. Selection Results

A total of 10,593 potentially relevant articles were identified through systematic searching. During the initial screening process, 8635 articles that were unrelated to the research topic were excluded. After a full review of the remaining 1958 articles, 89 studies that met the criteria were ultimately included. These studies examined the effects of different temperature conditions on rice growth and development. Based on the inclusion criteria, 1022 data sets were collected from the 89 selected studies, with the following distribution: Germination Stage (n = 148); Tillering Stage (n = 150); Heading Stage (n = 152); Jointing Stage (n = 136); Grain Filling Stage (n = 152); Maturation Stage (n = 142); and the overall effect of temperature fluctuations on the rice growth cycle (n = 142) (

Table 1. Dataset summary based on inclusion criteria.

TR	CT	N	Each Developmental Cycle
18–35 °C	18 °C	148	Germination Stage
18–35 °C	18 °C	150	Tillering Stage
18–35 °C	18 °C	152	Heading Stage
18–35 °C	18 °C	136	Jointing Stage
18–35 °C	18 °C	152	Grain Filling Stage
18–35 °C	18 °C	142	Maturation Stage
18–35 °C	18 °C	142	Total growth period
18–35 °C	18 °C	1022	Overall development stage

TR: temperature range; CT: control temperature; N: number of data sets.

).

3.2. Effects of Temperature Fluctuations on Rice Development Stages

Based on the data from various studies, a meta-analysis was conducted, and the results indicated that increasing temperatures accelerated the growth and development rate of rice. The overall mean effect size was −1.1444 (CI: −1.4524; −1.3704; Figure 1A,

Table 2. Random-effects model calculation results (SE represents the standard deviation; the Z-value is used to assess the statistical significance of an effect; p represents significance; Ci.LB and CI.UB represent 95% upper and lower confidence intervals; LOGLIK is used to measure the goodness of fit of the model, optimize parameter estimation, and compare the performance between models; AIC is the Akaike Information Criterion, which is used to balance the goodness of fit and complexity of the model; BIC is the Bayesian Information Criterion, which is also an indicator for model selection).

Variable	Estimate	SE	Z	p	Ci.LB	CI.UB	LOGLIK	AIC	BIC
Overall development stage	−1.1444	0.0209	−67.4327	<0.0001	−1.4524	−1.3704	−1105.4811	2214.9622	2224.8999
Germination stage	−1.1364	0.0479	−23.7438	<0.0001	−1.2302	−1.0426	−132.8781	269.7563	275.7908
Tillering stage	−1.2664	0.044	−28.771	<0.0001	−1.3527	−1.1801	−119.1809	242.3617	248.3963
Heading stage	−1.7671	0.0564	−31.359	<0.0001	−1.8775	−1.6566	−160.8919	325.7838	331.8184
Jointing stage	−1.3204	0.0462	−28.5829	<0.0001	−1.411	−1.2299	−133.8815	271.763	277.7976
Grain filling stage	−1.2246	0.0463	−26.4291	<0.0001	−1.3154	−1.1338	−129.0545	262.1089	268.1435
Maturation stage	−1.8471	0.0649	−28.4593	<0.0001	−1.9743	−1.7199	−181.8966	367.7931	373.8277
Total growth period	−1.1623	0.0466	−24.9658	<0.0001	−1.2535	−1.071	−131.0792	266.1584	272.193

, Supplementary Figure S1). Significant differences were observed in the responses of different rice growth stages to temperature changes (Figure 1B). Specifically, the effect sizes for the jointing and maturation stages were relatively small, at −1.77 and −1.85, respectively, suggesting that temperature increases had the most notable accelerating effects during these stages. As the temperature increased, the development rates during these two stages exhibited a distinct acceleration, with higher temperatures having a stronger impact. Although the effect sizes for the germination stage (−1.14) and the grain filling stage (−1.22) were larger, their responses were weaker compared to the jointing and maturation stages. Overall, increasing temperatures shortened the rice growth cycle and speeded up the development rate (Figure 1C). When temperature was treated as a continuous variable, it was observed that as the temperature rose above 25 °C, compared to lower temperatures (below 25 °C), the development cycles of rice in all stages were significantly shortened (Figure 1D).

3.3. The Impact of Temperature Increase on the Developmental Stages of Rice

This study assessed the impact of temperature variations on the development rate across six major growth stages of rice (germination, tillering, heading, jointing, grain filling, and maturation) using meta-analysis. The analysis of the response curves for each growth stage indicated that as temperature increases, the developmental cycles of rice significantly shorten. The effect sizes for all stages were negative, and when the individual case effect sizes were fitted to a nonlinear regression model, the results showed a clear intensifying trend with rising temperatures (Figure 2). This indicates that higher temperatures significantly accelerate the growth rate of rice.

3.4. Best Developmental Temperature for Each Growth Stage of Rice

In this study, the effect of temperature variations on the developmental cycles of six major growth stages of rice (germination, tillering, heading, jointing, grain filling, and maturation) was assessed using a meta-analysis with a mixed-effects model. The study also predicted the optimal developmental temperature for each stage. The results indicate that, in general, increasing the temperature accelerated the developmental processes across all growth stages of rice, though the optimal temperature for each stage varied.

As the temperature increases, the developmental period of the germination stage significantly shortens, and the growth rate accelerates. The overall average effect size is −1.1364 (CI: −1.2302; −1.0426; Figure S2, Table 2). The model predicts that the germination stage reaches its fastest development rate at 30 °C. Beyond 30 °C, the effect of temperature on this stage begins to diminish, suggesting that 30 °C is the optimal temperature for germination (Figure 3A, Table S1). Above 30 °C, the acceleration effect of temperature on germination noticeably declines.

Similarly, the tillering stage accelerates with increasing temperature, with an overall average effect size of −1.2664 (CI: −1.3527; −1.1801; Figure S3, Table 2). Although the optimal development temperature for this stage was not precisely calculated in this study, the results indicate that when the temperature exceeds 22 °C, the response of the tillering stage to temperature gradually intensifies, exhibiting significant temperature sensitivity (Figure 3B, Table S1).

In the heading stage, an increase in temperature also significantly shortens the developmental period, reflected by an accelerated growth rate, with an overall average effect size of −1.7671 (CI: −1.8775; −1.6566; Figure S4, Table 2). When the temperature exceeds 22 °C, the response of the heading stage to temperature intensifies, and as the temperature rises to 30 °C, the developmental period is its shortest, with the fastest growth rate (Figure 3C, Table S1). Beyond 30 °C, the influence of temperature on the heading stage begins to weaken.

During the internode elongation stage, an increase in temperature significantly shortens the developmental period and accelerates the growth rate, with an overall average effect size of −1.3204 (CI: −1.411; −1.2299; Figure S5, Table 2). According to the model predictions, the optimal developmental temperature for this stage is 32 °C. When temperatures exceed 32 °C, the influence of temperature on the internode elongation stage begins to weaken, showing a declining trend in its effect on this stage (Figure 3D, Table S1).

During the grain filling stage, an increase in temperature also accelerated the developmental rate, with an overall average effect size of −1.2246 (CI: −1.3154; −1.1338; Figure S6, Table 2). Although the optimal developmental temperature for this stage was not precisely calculated, the results indicate that when temperatures exceed 22 °C, the response of the grain filling stage to temperature gradually intensifies, demonstrating a strong temperature sensitivity (Figure 3E, Table S1).

The development of rice during the maturation stage is also significantly affected by increased temperatures, with a shortened developmental period and accelerated developmental rate. The overall average effect size is −1.8471 (CI: −1.9743; −1.7199; Figure S7, Table 2). Specifically, when temperatures exceed 22 °C, the response of the maturation stage to temperature intensifies, and when the temperature reaches 30 °C, the developmental period is the shortest, with the fastest developmental rate (Figure 3F, Table S1). Beyond 30 °C, the influence of temperature on the maturation stage begins to decrease.

In general, the increase in temperature accelerated the developmental cycles of rice at all growth stages, although the optimal development temperature varied for each stage. For the germination, jointing, and maturation stages, temperatures around 30 °C provided the best growth conditions, while the optimal temperature for the elongation stage was 32 °C. Although the precise optimal developmental temperature for the tillering and grain filling stages could not be calculated, we observed a clear accelerating effect of higher temperatures on these stages.

3.5. Impact of Temperature Fluctuations on the Total Growth Period

This study further explored the effects of temperature on the total growth duration of rice and conducted a mixed-effects model analysis based on indica and japonica rice. The results indicate that elevated temperatures significantly shorten the total development period of rice and accelerate the growth rate across all stages. Within the temperature range of 18–35 °C, temperature increases had a pronounced effect on the overall growth cycle of rice. As the temperature rose, the total development period of rice gradually shortened, with the growth rate accelerating (Figure 4A). Specifically, when temperatures exceeded 22 °C, the effect on the total growth cycle intensified, reaching its peak at 32 °C, where the development period was shortest and the growth rate fastest. However, temperatures above 32 °C resulted in a diminishing effect on the acceleration of the growth cycle, showing a saturation trend in the temperature effect (Figure 4B, Table S1). After analyzing the growth cycles of both the Indica and Japonica varieties, the results reveal that when temperatures are between 28 and 32 °C, both varieties reach their maximum growth rates (Figure 4C). Within this temperature range, all six growth stages and the total growth period exhibit a significant acceleration. Furthermore, once temperatures exceed 32 °C, the impact on both varieties begins to gradually decrease.

3.6. Sensitivity Analysis

Funnel plots and radar charts were used to assess whether the results were influenced by publication bias. Additionally, the reliability of our results was validated through the calculation of the fail-safe number. The findings indicate that the funnel plot (Figure 5A) showed a z-value of −11.6625 (p < 0.0001), while the radar chart (Figure 5B) and the fail-safe number (n = 652,412) both confirmed the reliability of our results.

4. Discussion

This study used a meta-analysis approach, combined with a mixed-effects model, to investigate the effects of rising temperatures on the growth stages and total development cycle of rice, while also predicting the optimal development temperatures for different growth stages. The results show that higher temperatures significantly accelerated the development rate of rice across all growth stages and revealed varied responses to different temperature ranges during development. Notably, in the temperature range of 28–32 °C, the development rate of rice was maximized. These findings provide scientific support for rice cultivation strategies in the face of future climate change.

4.1. The General Acceleration Effect of Temperature on Rice Growth

One of the core findings of this study is that higher temperatures generally accelerate the developmental rate of rice at all growth stages. In particular, when the temperature is in the range of 28–32 °C, the developmental rate of all six growth stages and the total growth period shows the fastest increase. This result is consistent with many related studies, further confirming the critical role of optimal temperature ranges in crop growth [22,23,24]. Previous studies have shown that temperature variations have different impacts on the growth stages of rice. This study conducts a meta-analysis to systematically integrate temperature variables from multiple studies and explores the extent of temperature’s impact on the rice growth cycle and its six distinct growth stages. Optimal temperatures can promote physiological processes such as cell division and photosynthesis, thereby accelerating crop growth. However, excessively high temperatures can inhibit crop growth, which is also reflected in our study [25,26,27]. Specifically, when the temperature exceeds 32 °C, the acceleration effect on the developmental stages gradually weakens, indicating that high temperatures have a threshold effect on rice growth.

4.2. Temperature Response Differences Across Growth Stages

Through the analysis of temperature response curves for each developmental stage, we found that the sensitivity to temperature varies across different growth stages. For example, 30 °C and 32 °C were predicted to be the optimal temperatures for the germination and heading stages, respectively, while 32 °C was identified as the best temperature for the jointing stage. These findings are consistent with existing research, which has shown that rice exhibits different temperature responses at various growth stages. For instance, the germination stage is highly sensitive to temperature, with suitable temperatures promoting seed germination, while excessively high temperatures can inhibit this process [28,29,30,31]. During the heading stage, high temperatures may accelerate pollen division and flowering, but temperatures that are too high can reduce pollen viability, thus impacting yield [32,33,34]. Therefore, understanding the optimal development temperature for each stage is crucial for improving rice yield.

4.3. Temperature Response Differences Between Rice Varieties

This study also analyzed the temperature response of indica and japonica rice. The results showed that both varieties reached their maximum growth rates within the temperature range of 28–32 °C. This indicates that both varieties exhibit similar growth responses in the optimal temperature range. However, due to the genetic differences between varieties, their adaptability to temperature changes may vary subtly. Previous studies have shown that Japonica rice is more cold-tolerant than Indica rice, while under high-temperature conditions, Indica rice may exhibit a higher growth rate [35,36]. Therefore, future research should focus on exploring the optimal growing environments for different rice varieties in varying temperature ranges, taking into account the specific characteristics of each variety.

4.4. Potential Impacts of Climate Change on Rice Growth

The results of this study provide important insights into rice production under climate change. As global temperatures continue to rise, the impact of increased temperatures on rice growth will become more pronounced. In particular, when temperatures exceed 32 °C, the accelerated growth effects of high temperatures will gradually weaken or even reverse, potentially negatively affecting future rice production [37,38]. Therefore, it is recommended that rice cultivation practices be adjusted in response to future climate forecasts. This could include measures such as modifying sowing dates, optimizing water management, and selecting heat-resistant varieties, in order to mitigate the adverse effects of high temperatures on rice growth.

4.5. Limitations of the Study and Future Directions

Although this study integrates a large amount of data through meta-analysis, there are still some limitations. Firstly, the data used in the study primarily come from the published literature, which may introduce data bias, especially in regions or time periods with small sample sizes. Secondly, while the mixed-effects model controls for heterogeneity between studies, it cannot completely eliminate the influence of other environmental factors such as light, soil moisture, and others, which may have significant effects on rice growth in real cultivation settings. Future research could combine laboratory and field experiments to further validate the impact of different temperature ranges on the various growth stages of rice and explore the interaction effects between temperature and other environmental factors.

5. Conclusions

This study, through a meta-analysis combined with insights from various studies on the impact of temperature variations on rice growth, reveals the specific effects of temperature changes on the development rate of rice. Subgroup analysis was conducted to further explore the differential impacts of various temperature ranges on the different growth stages of rice. The results indicate that as temperatures increase, the developmental rate of rice significantly accelerates across all growth stages. Within the temperature threshold range of 18–35 °C, the optimal temperature for maximum growth speed and the shortest overall developmental cycle across all growth stages was identified as 28–32 °C. With the growing impact of climate change, optimizing rice cultivation environments has become a critical strategy to ensure stable and increased yields. This study provides robust data support and a solid theoretical foundation for developing more precise strategies to optimize rice-growing conditions.