Physiological effects of the brown seaweed Ascophyllum nodosum) and humic substances on plant growth, enzyme activities of certain pepper plants grown under salt stress.

This study was aimed to examine the effects of seaweed extract (SW) and humic acid on the fruit yield, dry weight (DW%), protein, proline, lipid peroxidation (LPO) and antioxidative enzyme activity of pepper plants (Capsicum annuum L.) grown under saline conditions (100 mM). The obtained results indicated that salinity stress affected deleteriously plant growth and all other parameters. Besides, the treatment of seaweed (SW) and humic acid (HA) improved vegetative growth in the plant at all concentration levels applied under salinity conditions. Leaf fresh and dry weight was increased by all SW and HA applications in salinity stressed plant compared to those of control. Furthermore, there was a significant improvement in antioxidant enzyme activity, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) activities in the plant under salt stress and treated with SW and HA compounds. It suggests that seaweed and humic acid can enhance salt stress tolerance and leads to conservation of pepper plant against oxidative stress.