High temperature is one of the most important environmental factors influencing rice growth, development, and yield. Therefore, it is important to understand how rice plants cope with high temperatures. Herein, the heat tolerances of T2 (Jinxibai) and T21 (Taizhongxianxuan2hao) were evaluated at 45 °C, and T21 was found to be sensitive to heat stress at the seedling stage. Analysis of the H₂O₂ and proline content revealed that the accumulation rate of H₂O₂ was higher in T21, whereas the accumulation rate of proline was higher in T2 after heat treatment. Meanwhile, transcriptome analysis revealed that several pathways participated in the heat response, including “protein processing in endoplasmic reticulum”, “plant hormone signal transduction”, and “carbon metabolism”. Additionally, our study also revealed that different pathways participate in heat stress responses upon prolonged stress. The pathway of “protein processing in endoplasmic reticulum” plays an important role in stress responses. We found that most genes involved in this pathway were upregulated and peaked at 0.5 or 1 h after heat treatment. Moreover, sixty transcription factors, including the members of the AP2/ERF, NAC, HSF, WRKY, and C2H2 families, were found to participate in the heat stress response. Many of them have also been reported to be involved in biotic or abiotic stresses. In addition, through PPI (protein–protein interactions) analysis, 22 genes were identified as key genes in the response to heat stress. This study improves our understanding of thermotolerance mechanisms in rice, and also lays a foundation for breeding thermotolerant cultivars via molecular breeding.

Drought stress is a major environmental constraint that limits rice (Oryza sativa L.) production worldwide. In this study, we investigated the effects of drought stress at the booting stage on rice leaf physiological characteristics and yield. The results showed that drought stress would lead to a significant decrease in chlorophyll content and photosynthesis in rice leaves, which would affect rice yield. Three different rice varieties were used in this study, namely Hanyou73 (HY73), Huanghuazhan (HHZ), and IRAT109. Under drought stress, the chlorophyll content of all cultivars decreased significantly: 11.1% and 32.2% decreases in chlorophyll a and chlorophyll b in HHZ cultivars, 14.1% and 28.5% decreases in IRAT109 cultivars, and 22.9% and 18.6% decreases in HY73 cultivars, respectively. In addition, drought stress also led to a significant decrease in leaf water potential, a significant increase in antioxidant enzyme activity, and an increase in malondialdehyde (MDA) content, suggesting that rice activated a defense mechanism to cope with drought-induced oxidative stress. This study also found that drought stress significantly reduced the net photosynthetic rate and stomatal conductance of rice, which, in turn, affected the yield of rice. Under drought stress, the yield of the HHZ cultivars decreased most significantly, reaching 30.2%, while the yields of IRAT109 and HY73 cultivars decreased by 13.0% and 18.2%, respectively. The analysis of yield composition showed that the number of grains per panicle, seed-setting rate, and 1000-grain weight were the key factors affecting yield formation. A correlation analysis showed that there was a significant positive correlation between yield and net photosynthetic rate, stomatal conductance, chla/chlb ratio, Rubisco activity, and Fv/Fm, but there was a negative correlation with MDA and non-photochemical quenching (NPQ). In summary, the effects of drought stress on rice yield are multifaceted, involving changes in multiple agronomic traits. The results highlight the importance of selecting and nurturing rice varieties with a high drought tolerance, which should have efficient antioxidant systems and high photosynthetic efficiency. Future research should focus on the genetic mechanisms of these physiological responses in order to develop molecular markers to assist in the breeding of drought-tolerant rice varieties.

Cytokinins are key regulators of plant root development, but their dose-dependent effects on rice seedling roots and their physiological association with ethylene-related responses remain incompletely understood. In this study, rice seedlings were exposed to two exogenous cytokinins, 6-benzyladenine (6-BA) and kinetin (KT), at different concentrations for 3 and 6 d, and Ag⁺ was used as an inhibitor of ethylene action to evaluate its alleviating effect. Both 6-BA and KT significantly inhibited primary root elongation in a concentration- and time-dependent manner. At high cytokinin concentrations, primary root length was reduced by more than 60% relative to the control, accompanied by reductions in total root length, lateral root number, absorptive area, and root vigor, as well as increased MDA and ethylene levels. Ag⁺ partially alleviated cytokinin-induced primary root inhibition, with the strongest rescue effect observed near 0.08 μM. The recovery effect was particularly evident under moderate and high cytokinin concentrations. Correlation and principal component analyses further indicated that root morphological traits were negatively associated with MDA and ethylene but positively associated with root vigor. These results suggest that exogenous cytokinins restrict rice seedling root growth through a coordinated physiological response associated with ethylene accumulation and increased membrane lipid peroxidation, while Ag⁺ partially relieves this inhibition in association with mitigation of ethylene-related restriction. Because the study was based on short-term exogenous treatments and pharmacological inhibition, the findings should be interpreted as physiological evidence for ethylene-related involvement rather than direct proof of a complete signaling mechanism.

Sorghum (Sorghum bicolor), a drought- and salt-tolerant staple cereal, supports over 500 million people globally as food, fiber, and fuel. Auxin/Indole-3-Acetic Acid (Aux/IAA) proteins regulate auxin signaling for plant growth and stress responses. However, the Aux/IAA gene family in sorghum has not yet been comprehensively analyzed. In this study, a total of 42 SbAUX genes were identified, and phylogenetic analysis revealed that the SbAUXs could be clustered into five subfamilies. Structural analysis further revealed that these subfamilies exhibit distinct structural features, while structures remain relatively conserved within each subfamily. The expansion of SbAUX genes has been mediated by multiple duplication types, with whole-genome duplication (WGD) events identified as the predominant driving force. Interspecific collinearity analysis revealed that AUX genes have undergone purifying selection. Promoter analysis revealed that the SbAUX gene promoters contain stress-responsive elements including as-1 and STRE, and transcriptome analysis combined with RT-qPCR data implied a potential involvement of SbAUX genes in the response to salt and PEG stresses. These findings provide a preliminary theoretical basis for exploring sorghum’s molecular responses to stress, and the SbAUX genes identified herein might represent potential candidate genes for genetic improvement in sorghum.