Biochemical Responses of Grape cvs Sahani and Bidane-Sefid, Subjected to Progressive Drought

The influence of water deprivation on potted grape (Vitis vinifera L.) was investigated. Leaf Mass Area (LMA) and biochemical responses, including chlorophyll, total protein, peroxidase activity, soluble carbohydrates, photosynthesis and stomatal conductance were assessed in leaves of ‘Sahani’ and ‘Bidane sefid’ grape cultivars subjected to progressive drought (soil water potentials of: -0.2, -0.6, -1 and -1.5 MPa). The results indicated temporary reduction in the level of chlorophyll content under drought stress conditions. ‘Sahani’ contained a higher level of chlorophyll in comparison with ‘Bidane sefid’. Leaf Mass Area (LMA) was significantly decreased in ‘Bidane sefid’ under drought stress. LMA in ‘Sahani’ was recorded as higher than in ‘Bidane sefid’. Protein content was significantly reduced in -1 and -1.5 MPa treatment as compared with control (-0.2MPa), and the -0.6 MPa treatment. Peroxidase activity increased with increase in soil water potential. Increase in peroxidase activity in ‘Sahani’ was higher than in ‘Bidane sefid’ in comparison with control. The study revealed that mild drought stress (-0.6 MPa) affects photosynthesis while moderate (-1 MPa) and severe (-1.5 MPa) drought stresses affected chlorophyll, protein, peroxides activity as well as soluble carbohydrate levels. The results, in total indicated that ‘Sahani’ was of a higher tolerance to drought conditions as compared with ‘Bidane sefid’.