Foliar sprays of 1-MCP, CPPU, or KNO3 improve mango physiology following chilling by promoting stomatal opening

Chilling is a major abiotic stress that impairs physiological functions and reduces crop productivity, particularly in tropical and subtropical species. Mango trees (Mangifera indica L.) are especially sensitive to chilling events, notably when cold nights are followed by bright, sunny days—a condition referred to as ‘Cold Night–Bright Day’. Under these conditions, stomatal opening is impaired, leading to restricted gas exchange, disruption of the photosynthetic machinery, and subsequent physiological damage. The purpose of this study was to evaluate whether foliar sprays of agriculturally approved compounds could restore stomatal function and mitigate chilling-associated damage in mango. Following a night-chilling event (4 °C for 12 h), young and orchard-grown mango trees were sprayed with one of three treatments:(A) 1-Methylcyclopropene (gaseous release, 3.8 % 1-MCP, Rimi, LTD), N-(2-Chloro-4-pyridyl)-N'-phenylurea (CPPU; 240 µM with surfactant), or potassium nitrate (KNO₃; 100 mM with surfactant). Across independent experiments, all treatments significantly increased stomatal conductance, improved CO₂ assimilation, and reduced chilling-induced physiological impairment compared with untreated cold-stressed controls. No negative effects on PSII efficiency or chlorophyll content were observed.
These findings demonstrate that post-chilling foliar sprays with 1-MCP, CPPU, or KNO₃ effectively alleviate stress symptoms in mango by promoting stomatal reopening and photosynthetic recovery. By offering simple, practical treatments based on compounds already registered for agricultural use, this study highlights sustainable strategy to improve resilience of mango and other chilling-sensitive crops under increasingly variable climatic conditions.