Abstract
The experiment was conducted to observe the influence of Sea salt salinity (0, 0.15, 0.3, 0.6, 0.9 and 1.2% Sea salt corresponding to ECiw of 0.6, 3.51, 5.23, 9.23, 12.81 and 16.67dS.m-1 , respectively) on seedling growth and the physiological, biochemical and mineral parameters of growth in Vachellia nilotica subsp indica (Benth.) Kyal & Boatwr. (Syn. Acacia nilotica var. indica (Benth.) A.F. Hill). The ECiw of the irrigation medium corresponding to 50% reduction in various growth parameters, varied substantially from 8.16dS.m-1 (based on number of leaves) to 19.07dS.m-1 (based on stem length). On average basis 50% reduction in seedling growth performance, when all morphological parameters were taken into consideration corresponded to 10.64 ± 1.71 dS.m-1 . Excluding the parameter of stem length that gave relatively higher value, 50% reduction in other parameters corresponded to an average value of 8.76 ± 0.338 dS.m-1 . The salt tolerance index (STI) was high (> 90) in control and low salinity, moderate (50-90) in salinity from 5.23 to 12.81dS.m-1 and low (< 50) in extreme salinity. STI slightly increased under low salinity and related to ECiw in a quadratic fashion. The response breadths of V. nilotica on the basis of different parameters of seedling growth ranged from 0.6198 to 0.9497 (mean niche breadth = 0.7701 ± 0.0469) on salinity gradient of 0.6 to 16.67dS.m-1 . Foliar concentrations of protein, sugars, proline and phenols increased significantly with the salt stress and the pigments (chlorophylls and carotenoids) concentrations posed a declining behaviour. There was very high increase in foliar Na and Cl contents (317.88 and 253.07% over control, respectively) under extreme salinity of ECiw: 16.67dS.m-1 . Foliar K concentration although increased substantially with salinity but K/Na ratio declined in treatments of higher salinities (ECiw: ≥ 9.23 dS.m-1 ).
