Salinity Effects on Growth and Water Relations of some Desert Range Plants

Abstract

The present work was carried out on a number of range species, namely Chloris gayana, Panicum turgidum, Panicum antidotale, Panicum maximum, Panicum coloratum, Oryzopsis miliacea, Medicago sativa, and Crotalaria aegyptiaca. The study concerned growth and water relations, of the species grown under different conditions of NaCl salinisation ranged between 0.36 and 10.06 atm. osmotic pressure of the culture solution. The species exhibited great reduction in their vegetative as well as yield of dry matter with increasing salinity of the external soil solution. The percentage decrease in yield (on dry wt. basis) at the fuiting stage was 65% in Chloris gayana, 80% in Panicum antidotale, 72% in Panicum maximum, and 75% in Panicum chloratum. Water expenditure was greatly suppressed with increase in concentration of the external soil solution. Such increase reduced transpiration rate to about 50% of that of the control in most of the species. This may be chiefly due to the considerable increase in water saturation deficit at these higher levels of salinity. The osmotic pressure of shoot sap increased progressively with increasing salinity in all the species and in all stages of development. The magnitude of variation in the osmotic pressure also differed in the different species and at the different stages of development being wider in the mature stages than in the young ones. The present investigation visualizes the significance of Chloris gayana as a salt tolerant range species that could be grown in areas where saline irrigation is applied. At the highest level of salinity (10 atm). the dry matter production in Chloris gayana was greater than in the other sepcies and even than that in Medicago sativa growing under nonsaline conditions. The salt tolerance of Chloris gayana may be due to its relatively high osmtoic pressure and its ability to accumulate more salts in the cell sap.