Exogenous spermidine enhances chilling tolerance of tomato (Solanum lycopersicum L.) seedlings via involvement in polyamines metabolism and physiological parameter levels

摘要

The aim of the study was to elucidate the effect of exogenous spermidine (Spd) on polyamines (PAs) metabolism and physiological parameter levels in the leaves of tomato under chilling stress. Chilling-sensitive cultivar cv. Moneymaker seedlings were treated with Spd under chilling stress (15/6 degrees C). In this study, exogenous Spd could alleviate the damage induced by chilling stress, which was involved in the increase of maximum fluorescence ratio (F-v/F-m) and compatible solutes (soluble sugars and proline) contents, as well as the decrease of malondialdehyde (MDA) and reactive oxygen species (ROS) accumulation in leaves. Exogenous Spd caused much greater increases in free and conjugated endogenous Spd and spermine (Spm) concentrations. Moreover, during chilling stress conditions, exogenous Spd enhanced the activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), as well as diamine oxidase (DAO) and polyamine oxidase (PAO). Additionally, exogenous application of Spd enhanced the activities and expressions of antioxidant enzymes and genes. All of these suggested that Spd decreases chilling stress in tomato plants, through increasing compatible solute content, modulating PAs metabolism and ROS scavenging system.