Drought induced changes in growth, leaf gas exchange and biomass production in Albizia lebbeck and Cassia siamea seedlings.

ABSTRACT

Diurnal trends in net photosynthesis rate (PN ), stomatal conductance (gs ), water use efficiency (WUE) and biomass were compared in six-month-old seedlings of Albizia lebbeck and Cassia siamea, under different levels of drought stress. The potted plants were subjected to four varying drought treatment by withholding watering for 7 (D1), 14 (D2) and 25 (D3) days. The fourth group (C) was watered daily and treated as unstressed (control). Species differed significantly (p<0.001) in their physiological performance under varying stress conditions. Higher PN of 11.6 ± 0.05 in control followed by 4.35 ± 0.4 in D1 and 2.83 ± 0.18 @mol m-2 s-1 in D2 was observed in A. lebbeck. A significant (p<0.001) reduction in PN was observed in C. siamea ( C 7.65 ± 0.5 @mol m-2 s-1, D1, 2.56 ± 0.33 @mol m-2 s-1 and D2, 1.4 ± 0.01 @mol m-2 s-1 ) at 9 hr. A positive correlation was seen between PN and gs (A. lebbeck, r2= 0.84; C. siamea, r2= 0.82). Higher WUE was observed in C. siamea (D2, 7.1± 0.18 @mol m-2 s-1; D3, 8.39 ± 0.11 @mol m-2 s-1) than A. lebbeck, (control, 7.58 ± 0.3 @mol m-2 s-1 and D3, 8.12 ± 0.15 @mol m-2 s-1). The chlorophyll and relative water content (RWC) was more in A. lebbeck than C. siamea. Maximum biomass was produced by A. lebbeck than C. siamea. From the study, one could conclude that A. lebbeck is better than C. siamea in adopting suitable resource management strategy and be best suited for the plantation programs in the semi-arid dry lands.