Effects of different types of polyamine on growth, physiological and biochemical nature of lettuce under drought stress

This study explored the effects of drought stress on scattered leaf lettuce seedlings and the effects of different types of polyamines (PAs) on the morphological indexes and antioxidant enzyme activities of scattered leaf lettuce. The drought-sensitive variety Victoria crispy was used as the plant material, and 10% Polyethylene Glycol (PEG) 6000 was used to simulate drought stress. Foliar applications of 0.1 millimoles per litre of three polyamines [putrescine (Put), spermidine (Spd) and spermine (Spm)] were performed at the seedling stage (the control group was sprayed with water). The morphological indices and antioxidant enzyme activity were recorded on the eighth day after treatment. The results showed that drought stress significantly decreased the morphological indices of scattered leaf lettuce, and spraying different types of PAs had a mitigating effect. Drought stress significantly reduced the ascorbic acid peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activity, increased the content of malondialdehyde (MDA), and exogenous polyamine spraying significantly affected the antioxidant enzyme activity. Among the polyamines, Put showed the most noticeable effect of mitigation. Drought stress had a significant effect on the morphological and antioxidant enzyme activities of scattered leaves lettuce, and Put was the most effective PA to increase drought tolerance.