Salt stress severely restricts the growth of plants and threatens the development of agriculture throughout the world. Worldwide studies have shown that exogenous melatonin (MT) can effectively improve the growth of plants under salt stress. Through a meta-analysis of 549 observations, this study first explored the effects of salt stress characteristics and MT application characteristics on MT regulated plant growth under salt stress. The results show that MT has a wide range of regulatory effects on plant growth indicators under salt stress, of which the regulatory effect on root indexes is the strongest, and this regulatory effect is not species-specific. The intensity of salt stress did not affect the positive effect of MT on plant growth, but the application effect of MT in soil was stronger than that in rooting medium. This meta-analysis also revealed that the foliar application of a concentration between 100–200 μM is the best condition for MT to enhance plant growth under salt stress. The results can inspire scientific research and practical production, while seeking the maximum improvement in plant salt tolerance under salt stress.

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.

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.

Aerotaxis, the oxygen-directed motile behavior intrinsically linked to bacterial energy metabolism, serves as a fundamental survival and adaptive strategy for motile prokaryotes, including bacteria and archaea. This behavior enables these microorganisms to navigate along oxygen gradients and colonize metabolically optimal ecological niches. This review systematically synthesizes the latest research advancements in bacterial aerotaxis, focusing on the diverse signal-sensing mechanisms of aerotaxis receptors, which are primarily categorized into energy-dependent and direct oxygen-sensing types. Furthermore, we elucidate the distinct molecular mechanisms that underlie their oxygen signal perception and transduction. We also discuss the two major adaptive regulatory mechanisms of aerotaxis and its critical ecological functions in mediating microbe-host interactions, facilitating host colonization, and modulating biofilm formation. This work clarifies the evolutionary and ecological significance of aerotaxis in prokaryotic environmental adaptation and provides a comprehensive theoretical framework for future relevant research.