Growth and Physiology of Salicornia bigelovii Torr. at Suboptimal Salinity

Abstract

Salicornia bigelovii Torr. plants were grown in 5, 200, or 600 mol m-3 NaCl, representing suboptimal, optimal, and supraoptimal salinities, respectively. Shoot fresh and dry mass of plants grown at optimal salinity were more than 2 x higher than those grown at the other two salinities. In spite of the comparable growth reductions at sub- and supraoptimal salinities, the physiological responses, and presumably the causes of the growth reductions, were not the same at those two salinities. Water and osmotic potentials of the shoots decreased significantly with increasing salinity, but turgor potentials did not differ significantly among treatments. Differences in photosynthetic rates were not consistent with the differences in growth. Rates were significantly higher in plants grown at 5 mol m-3 NaCl when expressed relative to photosynthetic area, but when photosynthesis was expressed relative to the amount of chlorophyll, no significant differences were found among salinities. Stomatal conductance decreased with increasing salinity, resulting in a significantly higher transpiration rate at the lowest salinity than at the other two levels. Dark respiration was not significantly affected by salinity. Sodium concentration in shoots and roots increased with salinity. Potassium, calcium, and magnesium were highly concentrated in shoots and roots of plants grown at 5 mol m-3 NaCl. Excessive NaCl, however, induced calcium and magnesium deficiencies in plants grown at supraoptimal salinity.