Chilling tolerance improving of tomato seedling by drought stress pretreatment

Low temperatures lead to numerous physiological disturbances in the cells of chilling-sensitive plants, resulted in chilling injuries and death of tropical and subtropical plants such as tomatoes. In this study, the possibility of cold stress tolerance enhancement of tomato seedlings byimposing drought stress with 10 or 20 percent of polyethylene glycol (PEG) for 10 days was investigated in the greenhouse of agricultural faculty of Bu-Ali Sina University, Hamedan, Iran. The layout was factorial experiment in CRD design with four replications. After drought pretreatment, the seedlings were subjected to chilling 6 h/day at 3°C for 6 days. Drought pretreatment improved growth rate of tomato seedlings subjected to chilling stress as well as RWC, phenol, chlorophyll content and chlorophyll fluorescence ratio (Fv/Fm) when compared with the controls un-chilled seedlings. Interaction effects showed that highest value of root (2.25 g) and shoot fresh (4.4 g) weight, RWC (88.31 %), Fv/Fm(0.834) and total chlorophyll (1.62 mg/g F.W) were obtained in 0 % PEG under the chilling control. In contrast, the highest amounts of MDA (1.46 µm/g F.W) and phenol (10.86 mg/g F.W) content were obtained from 20% PEG and non-chilling stress. In general, results indicated that drought pretreatment could be used effectively to protect tomato seedlings from damaging effects of low temperatures stress at the early stages of growth.