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Melatonin plays an important role in plant growth and development. However, little information is available about melatonin regulating rice panicle structure and yield. This study explored the regulatory effects and mechanisms of melatonin spraying before the panicle differentiation stage on rice panicle structure and grain quality. The results showed that spraying melatonin before panicle differentiation increased rice yield, which was mainly reflected in the increase in spikelets per panicle and the percentage of filled grains. In addition, melatonin treatment significantly increased the panicle length. The results of panicle structure analysis showed that the increase in spikelets per panicle caused by melatonin was attributed to the significant increase in the number of secondary branches, total number of secondary branch spikelets, and number of spikelets per secondary branch. The results showed that melatonin can increase the content of zeatin, auxin, and gibberellin, and reduce the content of abscisic acid. These results showed that melatonin affected panicle structure by regulating hormone content, thereby improving yield. In addition, melatonin improves the processing quality, appearance quality, and nutritional quality of secondary branch grains. The above results indicate that application of melatonin improves the number of secondary branches and the quality of grainss on secondary branches. [ABSTRACT FROM AUTHOR]

Melatonin and abscisic acid, as major plant hormones, play important roles in the physiological and biochemical activities of crops, but the interaction between the two under salt stress is not yet clear. This study investigated the endogenous levels of melatonin and abscisic acid in rice by using exogenous melatonin, abscisic acid, and their synthetic inhibitors, and examined their interactions under salt stress. The research results indicate that melatonin and abscisic acid can improve rice salt tolerance. Melatonin alleviated the salt sensitivity caused by abscisic acid deficiency, increased antioxidant enzyme activity and antioxidant content in rice treated with abscisic acid synthesis inhibitors, and reduced total reactive oxygen species content and thiobarbituric acid reactive substance accumulation. Melatonin also increased the activity of key photosynthetic enzymes and the content of photosynthetic pigments, maintaining the parameters of photosynthetic gas exchange and chlorophyll fluorescence. In summary, melatonin alleviated the effects of abscisic acid deficiency on photosynthesis and antioxidant systems in rice and improved salt tolerance. This study is beneficial for expanding the understanding of melatonin regulation of crop salt tolerance. [ABSTRACT FROM AUTHOR]

Persistent organic pollutants seriously affect the growth and development of crops. 1,2,4-Trichlorobenzene (TCB), as one of the most widely used chlorobenzenes, can affect the yield of japonica rice. However, existing research on the effect of TCB on japonica rice yield is not in-depth, and a basic understanding of commonality has not yet been formed. In this study, 28 conventional japonica rice varieties were selected to investigate the effects of TCB stress on their yield, yield composition, and TCB accumulation. This study also evaluated the efficiency of conventional tolerance indices in evaluating the TCB stress tolerance of japonica rice. The results showed that TCB caused sustained inhibition of the growth of japonica rice, which was considerably manifested in plant height, root length, soil plant analysis development (SPAD), and dry weight at different growth stages. Under TCB stress, TCB accumulation in various tissues of japonica rice increased sharply. TCB stress reduces the yield of japonica rice by reducing the number of panicles per hill, the number of spikelets per panicle, the grain filling percentage, and the grain weight. Overall, the results of this study indicate that TCB stress can cause a decrease in the yield of japonica rice, and the decrease in panicle number is the main reason. The conventional tolerance index can effectively evaluate the tolerance of japonica rice to TCB. The results of this study are substantial for the breeding and cultivation of japonica rice., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yan, Zhang, Liu, Wang, Zhao, Huang and Niu.)