Abiotic stress-by-competition interactions drive hormone and nutrient changes to regulate Suaeda salsa growth

Abstract

During the growth cycle, complex and variable environmental conditions, such as salinity, moisture, nutrients, and plant-plant interactions, may prompt plants to modulate ecological strategies. As a typical halophyte, the response mechanism and adaptation strategy of Suaeda salsa to various abiotic stress-by-competition interactions are still unclear. In this study, we aimed to explore the responses of S. salsa to combined abiotic stress and competition conditions to gain further insights into the ecological adaptation of halophytes to stress conditions. In this study, we aimed to explore the responses of S. salsa to combined abiotic stress and competition conditions to gain further insights into the ecological adaptation of halophytes to stress conditions. In a pot experiment, we set five density gradients of 1, 3, 6, 9, and 12 plants and conducted salt and drought stress experiments to explore the ecological adaptation strategies under abiotic stress-by-competition and the direct and/or indirect effects of key endogenous hormones and nutrients on plant growth. The results demonstrated that drought and planting density were the main environmental factors that restricted growth. Drought decreased biomass accumulation and competition intensity and delayed reproductive phenology and senescence. Competition promoted early anthesis and fructescence and reduced the vegetative organ to reproductive organ ratio to improve fitness. Changes in hormone and nutrient levels driven by the environment directly and/or indirectly affected growth independently and/or jointly. Total leaf phosphorus content and the endogenous hormone strigolactones directly affected biomass in different interaction modes and had positive and negative effects, respectively. This study improves our understanding of the importance of hormones and nutrients in plant ecological adaptation strategies and provides an effective reference for explaining the physiological mechanisms of plant ecological adaptation.