Effect of Salinity on Growth and Development of Date Palm

Although date palm is classified as a salt resistant tree, however high level of salt in the soil or irrigation water has a considerable negative impact on its growth and productivity besides the reduction of survival rate of offshoots cultured in salty soil. This presentation will focus on the current aspects of our research work at the University of Basra to improve salt tolerance of date palm by exogenous application of some chemicals that have a positive effect on growth and fruiting of date palm under saline condition. Also we have done a series of research work to produce salt resistant date palm plantlets through callus culture and somatic embryogenesis under high concentration of NaCl salt. Sulfur is an essential nutrient that play role in plant development in reversing the adverse effects of abiotic stress because of its ability to scavenge free radicals that produced under salt stress and stimulate the anti-oxidative defense system. Sulfur also plays role in activation of several enzymes and the acidity that produced during elemental sulfur oxidation increases the availability of nutrients which enhance plant growth. To study the effect of sulfur on growth of offshoots of two date palm cultivars (‘Barhi’ and ‘Sayer’) grown in Basra, sulfur was added at three rates (0, 100 gm and 200 gm per offshoots). The offshoots cultured in salty soil (EC 15.9 ds/m). Results were taken after 7 months of treatment which showed that sulfur at level of 200gm caused a significant increase of offshoot height, leaf area, number of leaves and girth compared with control treatment. Also, sulfur application influenced biochemical characteristics of offshoots such as total chlorophyll, dry weight, carbohydrates, proline, protein, peroxidase enzyme activity and endogenous indolacetic acid content compared with control treatment. Sulfur at 200gm rate decreased catalase enzyme activity and abscisic acid content. Level of Na and Cl ions were decreased in leaves by sulfur treatment and improved salinity tolerance of offshoots by maintaining high ratio of K /Na ions. Calcium also used as a foliar spray or soil application by Polixal (8% Ca) and Rexene (9.7% Ca) which are a liquid commercial product as a source of Ca. Polixal added to the soil around the offshoots by rate of 15 and 30 ml per offshoot while Rexene used as a foliar spray at concentrations of 1000 and 2000 ppm. Results showed that Polixal at 30 ml per offshoots increased all vegetative criteria and biochemical contents of offshoots by the improvement of antioxidant defense system under salt stress. Another experiment was conducted on adult trees of ‘Sayer’ date palm cultivar grown in salty soil (Ec 17.2 ds/m). Treatments included addition of sulfur (200 and 400 gm/tree), calcium as calcium nitrate (100 and 200gm/tree)