NUTRIENT STATUS AND ENZYME ACTIVITY ALTERATION IN CUCUMBER SEEDLINGS AS A RESPONSE TO BORON DEFICIENCY

摘要

Cucumber (Cucumus sativus L. var. Beit alpha) seedlings were grown in two groups on boron-deficient (traces of boron) and boron-sufficient (10.0 μM boron) hydroponic media for 30 days under controlled conditions. At harvest, the concentrations of magnesium (Mg), iron (Fc), manganese (Mn), zinc (Zn) and copper (Cu) were determined in addition to boron (B) in the dry tissues of roots and leaves. The concentration of phenolic compounds in the roots was also determined. Peroxidase (POD) and catalase (CAT) enzyme activity was assayed in the fresh plant material. In addition, changes in the peroxidase and catalase isozyme patterns were also identified. The results showed that the vegetative growth of cucumber plants was negatively affected by boron deficiency. Biomass accumulation decreased by as much as 24.3% in the shoots and 49.1% in the roots. The nutrient concentrations in both the leaves and roots of B-stressed plants were substantially lower. Phenolic compounds were accumulated in significant amounts in the roots of deficient plants. The peroxidase and catalase enzyme activities were significantly increased in the tissues of deficient plants and new isozymes were induced or activated. The irregular biochemical changes occurring in B-deficient plants were explained as a plant physiological response to B-deficient conditions.