Spermidine induces physiological and biochemical changes in southern highbush blueberry under drought stress

Drought stress is one of the main environmental stresses that have effect on plant growth and development. Spermidine (SPD) plays an important role in the defense responses to drought stress in plants. In this study, we investigated the effects of exogenous SPD on plant growth, net photosynthetic rate (Pn), antioxidant enzyme activities, chlorophyll, malondialdehyde (MDA) and phytohormone contents in leaves of blueberry (Vaccinium corymbosum 'Misty') seedlings under drought stress. Drought stress severely reduced the relative water content (RWC), chlorophyll, Pn, specific leaf weight (SLW), indole-3-acetic acid, gibberellic acid and polyamine contents, while increased relative electrolyte conductivity (REC), MDA, total soluble sugar and abscisic acid (ABA) contents, the activities of SOD and POD. Compared with seedlings without SPD treatment, SPD increased the RWC, chlorophyll content, Pn, SLW, SOD and POD activities and decreased REC, MDA, total soluble sugar and ABA contents in seedlings. These results signified the role of SPD in alleviating the negative effects of drought stress on plants and suggested that SPD could be used as a potential growth regulator for improving plant growth under drought stress.