Influence of Soil Water Deficit on the Growth and Root Growth Potential of Dalbergia sissoo Seedlings in an Arid Environment

Leaf, shoot, ischolar_main growth and ischolar_main growth potential of Dalbergia sissoo Roxb. ex. DC. Prodr seedlings were studied at irrigation levels of 20 (W₁), 14 (W₂), 10 (W₃), and 8 (W₄) mm with a view to determine the optimum level of irrigation for better growth and development. Treatments were maintained by re-irrigation when water content of the soil reached 7.4 % in W₁, 5.6 % in W₂, 4.3 % in W₃, and 3.2 % in W₄. Seedlings in a control (W₅) were left without irrigation after maintaining the soil field capacity (10.7 %). Height, collar diameter, number of branches, leaves and ischolar_main growth potential decreased (P<0.01) with soil water stress. The differences in height and collar diameter between W₁ and W₂ treatments were not significant but the seedlings of W₃ had less height, collar diameter, number of branches, leaves, ischolar_main growth potential and ischolar_main dry weight. The stressed seedlings tended to maximize leaf area before the environmental condition become more adverse. Leaf area/ischolar_main dry weight ratio was high whereas ischolar_main/ shoot dry mass ratio was low for the seedlings under W₂ treatment. With increasing stress from W₂ to W₃, growth reduction was high and may be the critical point. Seedlings of W₅ treatment survived till ψs of -1.96 MPa. Thus W₂ treatment was the best where seedlings showed high above ground/ischolar_main dry weight ratio and was maintained by addition of half quantity of water than that in W₁. The results indicate that D. sissoo seedlings is moderately tolerant to water stress and had high growth when soil water status was >50% of soil field capacity.