The changes in growth and metabolic adaptation responses in Java plum seedlings exposed to Cassia javanica extract under salinity

Developing and employing new, sustainable, and eco-friendly biostimulants that enhance plant growth and alleviate the harmful effects of environmental challenges is a major focus for many researchers. Salt stress is a critical constraint on plant growth and a limiting factor in crop productivity, particularly during the early developmental stages in the nurseries. Syzygium cumini (L.) Skeels (Java plum) is an important fruit tree and widely cultivated in gardens as an ornamental plant. This study was designed to develop Cassia javanica subsp. nodosa leaf extract (CLE) as a new sustainable and eco-friendly biostimulant capable of triggering the metabolic adaptation to salt stress in Java plum seedlings grown in nurseries. CLE successfully mitigated reductions in growth, biomass yield, and secondary metabolite production caused by salinity. Although salt stress depressed morphological characters and biomass yield, CLE foliar spray enhanced these parameters. Moreover, CLE enhanced the ferric reducing antioxidant potential, catalase, and superoxide dismutase enzyme activities, increased phenolic content, and reduced hydrogen peroxide (H2O2) accumulation and lipid peroxidation. Additionally, CLE application increased seedling biomass and stimulated antioxidant activity, osmoprotectant accumulation, and overall tolerance to salinity stress. These observations provide new insights into CLE's potential as an eco-friendly biostimulant for enhancing salt tolerance in Java plum seedlings.