Melatonin, a key indoleamine compound intrinsic to life, is ubiquitously distributed across the plant kingdom in plants. As a plant growth regulator and biostimulant, melatonin plays a pivotal role in both increasing plant growth and bolstering resilience to stress. This review provides a comprehensive analysis of regulatory mechanisms plant growth and development and addresses biotic and abiotic stressors. We dissect the biosynthetic and metabolic pathways of melatonin in plants and elaborate on its roles in catalyzing plant growth, development, and antioxidant activities. Furthermore, our discussion delves into the ways in which melatonin manipulates plant morphology, physiology, redox systems, ion homeostasis, biomolecular content levels, and the expression of stress resistance genes or proteins. We additionally highlight its cooperative interaction with other endogenous hormones in mitigating the deleterious impacts of challenging environments. In essence, melatonin, as a multifunctional biological signaling molecule, offers the potential to increase crop yield even under adverse conditions by plant seed germination rates and promoting robust growth. Consequently, it as a compelling candidate for ecofriendly crop production strategies. This review is intended to serve as a theoretical guide to unravel the multifaceted regulatory mechanisms of melatonin in governing plant growth, development, and stress resistance.

Eucommia ulmoides Oliver. (E. ulmoides) is a species of small tree native to China. It is a valuable medicinal herb that can be used to treat Alzheimer’s disease, diabetes, hypertension, and other diseases. In addition, E. ulmoides is a source of rubber. It has both medicinal and ecological value. As ecological problems become increasingly prominent, accurate information on the cultivated area of E. ulmoides is important for understanding the carbon sequestration capacity and ecological suitability zoning of E. ulmoides. In previous tree mapping studies, no studies on the spectral characteristics of E. ulmoides and its remote sensing mapping have been seen. We use Ruyang County, Henan Province, China, as the study area. Firstly, using the 2021 Gao Fen-6 (GF-6) Wide Field of View (WFV) time series images covering the different growth stages of E. ulmoides based on the participation of red-edge bands, several band combination schemes were constructed. The optimal time window to identify E. ulmoides was selected by calculating the separability of E. ulmoides from other land cover types for different schemes. Secondly, a random forest algorithm based on several band combination schemes was investigated to map the E. ulmoides planting areas in Ruyang County. Thirdly, the annual NPP values of E. ulmoides were estimated using an improved Carnegie Ames Stanford Approach (CASA) to a light energy utilization model, which, in turn, was used to assess the carbon sequestration capacity. Finally, the ecologically suitable distribution zone of E. ulmoides under near current and future (2041–2060) climatic conditions was predicted using the MaxEnt model. The results showed that the participation of the red-edge band of the GF-6 data in the classification could effectively improve the recognition accuracy of E. ulmoides, making its overall accuracy reach 96.62%; the high NPP value of E. ulmoides was mainly concentrated in the south of Ruyang County, with a total annual carbon sequestration of 540.104835 t CM⁻²·a⁻¹. The ecological suitability zone of E. ulmoides can be divided into four classes: unsuitable area, low suitable area, medium suitable area, and high suitable area. The method proposed in this paper applies to the real-time monitoring of E. ulmoides, highlighting its potential ecological value and providing theoretical reference and data support for the reasonable layout of E. ulmoides.