The Influence of Water-Deficit Stress on Growth, Water Relations and Solute Accumulation in Wild Jujube (Ziziphus lotus)

Wild jujube, Ziziphus lotus, is a multipurpose xerophytic shrub of the Rhamnaceae family widely distributed in arid and semi-arid regions of Tunisia, where it occupies most soil types. The fruit is the edible part of the plant by local population. The reintroduction of this shrub requires the control of its multiplication in response to water shortage. This study aims to evaluate growth and water relations of wild jujube seedlings under water deficit stress. After multiplication and growth under well-watered conditions, water deficit stress was imposed to seedlings by controlled deficit irrigation to 40 and 70% of field capacity (FC) for 15, 30 and 45 days. Soil of control plants was maintained at 100% FC throughout the experiments. Best growth was recorded for control plants, while water deficit successively reduced dry matter production and leaf number per plant. In addition, relative water content of leaves and branch water potential decreased significantly under severe drought stress. Plants subjected to 40% FC, accumulated respectively, 1.5 and 15-fold more soluble sugars and proline in leaves than controls. There was a strong negative relationship identified between leaf proline concentration and branch water potential with R2 = 0.85, reflecting the importance of this amino acid ability for osmotic adjustment in Z. lotus.