The effect of humic acid on growth and some physiological responses in bermuda ‎grass subjected to salinity stress

In order to investigate effect of humic acid (HA) on growth and some physiological parameters of bermuda grass under salinity stress, a factorial experiment was cinducted. The first factor was humic acid at four levels ( 0, 50, 100 and 150 mg/l )  and the second factor was salinity at  four levels (0, 5, 7 and 9 ds/m ).  Results of variance analysis showed significant effects of the salinity and HA on plant growth parameters, photosynthetic pigments, malondialdehyde (MDA), proline and antioxidant enzyme activity. Results showed that salinity stress imposed negative effects on plant growth and productivity. In salinity conditions, fresh and dry weight, leaf area and photosynthetic pigments reduced, but proline, malondialdehyde, catalase and superoxide dismutase activities increased. HA application improved growth parameters and increased chlorophyll content, catalase and superoxide dismutase activities of bermuda grass subjected to salinity and provided significant protection against salinity stress compared to non-HA-treated plants. The highest salinity tolerance was obtained with 150 mg/l HA application. In general, the results indicated that HA application, by altering in some tolerant responses, could be effectively used to protect plants from the adverse effects of high salt concentration.