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

Abstract

Leaf, shoot, root growth and root 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 root 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, root growth potential and root dry weight. The stressed seedlings tended to maximize leaf area before the environmental condition become more adverse. Leaf area/root dry weight ratio was high whereas root/ 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/root 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.