Effect of Light, Temperature and Water Stress on Net Photosynthesis in Two Populations of Honey Mesquite

Abstract

Net carbon dioxide assimilation rates (PN) were measured for individuals from two Texas honey mesquite populations grown under controlled water stress, temperature, and light treatments. Maximum (PN) observed for the various tests ranged from 0.69 to 0.82 mg m-2 s-1. Net assimilation rates were significantly lower in the west Texas population than in the east Texas population under high and low water stress. Maximum (PN) at 1.35 mmol m-2 s-1 photon flux density were reached under low water stress at 20 degrees C and 30 degrees C for east and west Texas populations, respectively. The response of (PN) to light was similar to responses reported for other C3 species; and 81 to 99% of the variability in the data was accounted for by using a hyperbolic light response model. Light use efficiency was lower for the west Texas population, and for high temperature and water stress. High temperature and water stress treatments also caused substantial decreases in the estimated theoretical maximum net assimilation rates. Finally, the light saturation point of mesquite varied depending on population and water stress.