Great Basin Naturalist Memoirs


Rates of gaseous exchange were measured on selected desert shrubs native to the northern Mojave Desert to determine effects of varying chamber temperature, CO2 concentration, relative humidity, and root temperature in preliminary studies. Results indicate that changes in these parameters produced differences in the rates of photosynthesis and transpiration. Ceratoides lanata (Pursh) took up CO2 almost equally at 25 and 39 C. Doubling the CO2 concentration in the below-ambient range roughly doubled photosynthesis rates in C. lanata. Very small changes in relative humidity had marked changes in the photosynthesis and transpiration rates of four species studied, with greater effect on transpiration. Photosynthesis and transpiration increased, and water-use efficiency decreased in two species as soil temperature was increased from 9 to 29 C.