SODIUM RELATIONS IN DESERT PLANTS

Atriplex confertifolia (Torr, Frem.) Wats. seedlings were grown in soil irrigated with different salt levels. Maximum yields were obtained with a 50 me/liter NaCl treatment. Higher salt levels produced large, succulent leaves showing symptoms of nitrogen deficiency. Physiological effects of salt were noted as decreased chlorophyll, soluble protein, and nitrate and loss of nitrate reductase activity. Salt also reduced the uptake of Mg, K, and P. Net carbon assimilation rates were reduced presumably from salt-induced increases in respiration. Leaf water potential was decreased greatly by the salt levels, but transpiration levels at leaf temperature of 20°C did not correspond in that they were quite insensitive to salt levels. At 30°C, transpiration rates decreased with increasing salt indicating an improved water use efficiency.