Improvement of some physiological parameters of lily (Lilium spp.) under deficit irrigation conditions using foliar application of spermidine

Polyamines including spermidine play an important role in the tolerance of plants to water deficit stress. In order to investigate the effect of spermidine on physiological traits of Lilium under deficit irrigation stress, a factorial experiment was conducted in a completely randomized design with three replications. Treatments were four levels of water deficit (100, 75, 50 and 25% of Field Capacity) and different levels of spermidine (0, 1 and 2mM). Based on these results, severe deficit irrigation (25% of FC) increased proline and electrolyte leakage than control respectively by 174% and 55%. In contrast, decrease of carotenoids and proteins content (33% and 26%, respectively) were observed under severe deficit irrigation conditions compared to the well-watered conditions. Results showed that lower availability to water in the lilium plants, higher activities of enzymes (catalase, ascorbate peroxidase, peroxidase) and malondialdehyde stimulated, but decreased chlorophyll content of leaves. Also, under severe stress (25% of FC), exogenous application of spermidine (2mM) enhanced the the activity of enzymes and decreased the level of malondialdehyde. Therefore, foliar application of spermidine (2mM) and mild stress level (75% of FC) are a procedure capable to save water consumption and maintain the quality of Lilium shoot.