Irradience,  Temperature and Salinity Effects on Growth, Leaf Anatomy and Photosynthesis of Distichlis spicata (L.) Greene

The effects of irradiance, temperature, and salinity on growth, net CO ₂  exchange, and leaf anatomy of Distichlis spicata were investigated in controlled environment chambers. When plants were grown at low irradiance, growth rates were significantly reduced by high substrate salinity or low temperature. However, when plants were grown at high irradiance, growth rates were not significantly affected by temperature or salinity. The capacity for high irradiance to overcome depressed growth at high salinity cannot be explained completely by rates of net photosynthesis, since high salinity caused decreases in net photosynthesis at all environmental conditions. This salinity induced decrease in net photosynthesis was caused largely by stomatal closure, although plants grown at low temperature and low irradiance showed significant increases in internal leaf resistance to CO ₂  exchange. Increased salinity resulted in generally thicker leaves with lower stomatal density but no significant differences in the ratio of mesophyll cell surface area to leaf area. Salinity and irradiance during growth did not affect rates of dark respiration. The mechanisms by which Distichlis spicata tolerates salt appear to be closely coupled to the utilization of light energy. Salt-induced leaf succulence is of questionable importance to gas exchange at high salinity in this C ₄  species.

Project No. B-058-NMEX