Document Type : Research Paper
Department of Agronomy and Plant Breeding, Faculty of Agriculture, University of Zanjan, Zanjan, P.O.Box 313-45195, Iran
Department of Soil Science, Faculty of Agriculture, University of Tehran, Tehran, Iran
Depertment of Soil Science and Water Management, Faculty of Horticulture, Szent István University, Budapest, 29-43 Villányi ut, H-1118 Budapest, Hungary
Salinity stress is a brutal environmental stress which decreases the yield production of plants. Questions rise on which of the ionic stress or lack of water has deleterious effects on plants forage dry yield. Also, questions remain on whether the K+ reduction or Na+ accumulation is more important in forage dry yield reduction under salinity stress. The present experiment was conducted to answer the above questions in four alfalfa ecotypes. To do so, 6-7 weeks seedlings were irrigated with high salty water (EC=20dS m-1) and RWC, MSI, height, forage dry yield, Na+ and K+ were measured 1, 3, 6, 10, and 16 days after the salt shock. The results showed that one day after irrigation with saline water, all measured traits changed adversely. Salinity stress by decreasing K+ and increasing Na+ content reduced the growth of alfalfa plants. RWC reduction was less than K+ reduction or Na+ accumulation, so ionic stress had more deleterious effects on forage dry yield of alfalfa plants. Root cells had a higher content of K+ and Na+ ions compared with leaves, hence, they had a major defensive role against salinity stress. The K+/Na+ ratio reduction in saline condition was the main element for decreasing plant forage dry yield. The application of high salty water for irrigation of alfalfa plants is possible if there is a good subsoil drainage system to remove the leached saline water regularly from the soil. It is also suggested that foliar application of potassium may be ameliorate harmful effects of salinity stress in plant growth.