The Water Relations of Some Desert Plants in Death Valley, California

Abstract

The seasonal water relations of four plant species native to Death Valley were studied which were growing under both natural and irrigated conditions. These species included the winter annual, Camissonia claviformis , a summer-active herbaceous perennial, Tidestromia oblongifolia , and two evergreen perennials, Atriplex hymenelytra and, Larrea tridentata. Camissonia a plant with a high photosynthetic capacity had characteristics typical of most mesophytes under natural conditions and maintained high tissue water contents as well as high water and osmotic potential. Irrigation had little effect on these parameters for Camissonia. Tidestromia , which also has an unusually high photosynthetic capacity as well as a high rate of transpiration under natural conditions also has water balance characteristics not unlike many mesophytes although not to the same degree as Camissonia . The evergreen drought-enduring species which have a comparatively low photosynthetic capacity maintain low water and solute potentials at all seasons. Even at dawn when irrigated these species have low water potentials especially during the summer. In these xerophytes solute potential decreases during the course of the day. During the summer the plants under natural conditions have turgor pressures close to zero. The differential inherent photosynthetic capacities of these species are apparently strongly related to their inherent water balance characteristics.