Biochemical responses of sugar beet plant to phytoprotectants and vermicompost under moisture stress

In recent years, with the spread of drought and increasing demand for water, the need for water management in irrigation of plants has become more apparent. Present investigation studied yield-related biochemical responses of sugar beet to vermicompost and phytoprotectants to mitigate drought stress based on a split-plot-factorial design with three replications. The main plots consisted of irrigation at 90%, 70%, 50%, and 30% field capacity (FC). The subplots subjected to treatments comprised a factorial combination of vermicompost (0 and 7 Mg/ha) and foliar application of phytoprotectants [distilled water as a control, zinc (5μM), silicon (4mM), glycine betaine (4mM) and ascorbic acid (0.5mM)]. The findings showed that concentration of ascorbate peroxidase, catalase, dehydroascorbate reductase, glutathione peroxidase, and superoxide dismutase, were significantly enhanced under stress conditions. Despite the higher sugar percentage, the lower root yield and biomass were recorded in the plants irrigated with 30 and 50% FC. Sugar content increased gradually in response to increasing in water deficit (from 70% to 30% FC). Root yield increased insignificantly with zink, glycine betaine, and ascorbic acid treatments. The highest root yield was obtained at 70% FC that followed by other water regimes (90, 50, and 30% FC, respectively). Malondialdehyde increased with increasing stress level but it decreased when phytoprotectants, especially glycine betaine, were applied. Vermicompost treatment had positive effect on the prevention of lipid peroxidation.  It can be concluded that phytoprotectants and vermicompost protect sugar beet plants from drought-induced oxidative stress, and improve root and sugar yield by enhancing plant water-stress tolerance.