Role of Polyamines in Mitigating Salinity Stress in Ornamental and Food Crops.

Soil and irrigation salinity continue to have a major impact on the world's agriculture and horticulture, and loss of plant production is likely to worsen with global warming and climate change. Efforts to mitigate salinity stress and breed better salt-tolerant plants rely on our knowledge of plant response to abiotic stress at the physiological and molecular levels. Salinity usually leads to the accumulation of free and conjugated polyamines (PAs) in plant tissues. Putrescine (Put), and its derivatives spermine (Spm) and spermidine (Spd), perform critical functions by activating biochemical, physiological and molecular defense systems, thus reducing damage caused by salinity stress. Promoting endogenous levels of PAs can improve the salt tolerance of plants. Furthermore, the application of exogenous PAs has been shown to effectively mitigate salt stress across a range of commercially important plant species. This review critically examines the biosynthesis of PAs and their associated physiological, phytochemical, and molecular responses in plants under saline conditions. In addition, it evaluates the potential of PAs as a strategic tool for enhancing salinity tolerance. The review also highlights key gaps in current knowledge and proposes directions for future research to optimize the use of PAs in salinity stress management.