Differential responses to drought stress in leaves and roots of wild jujube, Ziziphus lotus

摘要

The aim of this study was to investigate the effects of drought stress induced by polyethylene glycol-6000 in wild jujube, Ziziphus lotus. One-month-old, hydroponically grown seedlings were subjected to three treatments, i.e. normal watering (-0.2 MPa), moderate (-1.2 MPa) and severe (-2.1 MPa) drought stress for 14 days under controlled climatic conditions. Plant growth was markedly reduced with increasing osmotic stress. The shoot water potential (PHI w) and leaf relative water content followed similar patterns and significantly decreased with increasing osmolality of solutions. As a consequence of drought, contents in proline and soluble sugars were found to be more elevated in leaves than in roots. The level of lipid peroxidation in terms of malonyldialdehyde contents increased in both leaves and roots of drought-stressed plants. Wild jujube displayed higher activities of antioxidant enzymes in the roots than in the leaves. Catalase and guaiacol peroxidase activities increased significantly indrought-stressed roots, whereas ascorbate peroxidase activity showed a slight decline with no significant changes. These findings suggest that Z. lotus was able to adapt to severe drought stress by accumulation of compatible solutes and by activation offree radical-scavenging enzymes. Overall, defence mechanisms in Z. lotus against oxidative stress are organized differently in plant tissues, with higher solute accumulation in leaves and increased activity of antioxidants in roots, during drought stress.