Seasonal Water Potential Components of Sonoran Desert Plants

Monson, R.; Smith, S.

Seasonal water potential components were measured for 7 Sonoran Desert plant species representing a variety of growth forms. Three of the species (Amsinckia intermedia, Erodium cicutarium and Baccharis sarothroides), which occupy the most mesic microhabitats, possessed the highest osmotic potentials and lowest pressure potentials with very litte seasonal adjustment in either parameter. Two species (Larrea tridentata and Atriplex polycarpa), which experienced substantial periods of water stress, had relatively low osmotic potentials and high pressure potentials with seasonal adjustments occurring in both. Two species (Encelia farinosa and Olneya tesota) exhibited intermediate responses for dawn plant water potential. Encelia exhibited intermediate osmotic and pressure potential values. In Olneya these latter values were very similar to those for Larrea and Atriples. The capacity for osmoregulation was noted in 4 of the 7 spp., with fluctuations in the osmotic potential at full turgor ranging form 0.3-0.8 Mpa [pascals]. Adjustments in tissue elasticity and pressure potential were noted in 4 of the species. In general these adjustments allow the species to maintain higher gurgor pressures at most relative water contents during periods of drought stress. Apparently, a plant's capacity to avoid wate stress is reflected in its water potential components.

Seasonal Water Potential Components of Sonoran Desert Plants

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