Effect of L-Ornithine application on improving drought tolerance in sugar beet plants

The objective of this research was to determine the foliar application of L-ornithine (0.0, 0.30 and 0.60 mM) as a precursor of polyamines, at vegetative stage was on antioxidant defense and growth of drought stressed sugar beet plants grown under clay and sandy soil conditions. Two water irrigation treatments (80% and 40% Field capacity) were carried out on sugar beet plants grown in pots under greenhouse conditions. Water stress resulted in significantly decrement in growth parameters including root diameter, root and shoot weights per plant compared with corresponding control plants. The results showed that drought stress significantly affected most biochemical characteristics of plants. Photosynthetic pigments contents, free amino acids and peroxidase enzyme activity were decreased, while catalase enzyme activity and lipid peroxidation was increased with drought stress. On the other hand, foliar application of L-ornithine effectively alleviated harmful effects caused by drought stress on root length, root and shoot weights of sugar beet plants, especially under sandy soil conditions. The results cleared that ameliorating the negative effects of drought stress through exogenously applied L-ornithine associated with improved photosynthetic pigments, protein profile, lipid peroxidation, antioxidant enzymes; catalase and peroxidase, total soluble sugars and total amino led to increasing drought tolerance of sugar beet plants.