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Larrea tridentata is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States. We examined relationships between gasexchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of L. tridentata over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA. The soil wetting front did not reach 0.6 m, and soils at depths of 0.6 and 0.9 m remained dry throughout the summer, suggesting that L. tridentata extracts water largely from soil near the surface. Surface soil layers (max) occurred in early summer (21.3 � mol m-2 s-1), when pre-dawn xylem water potential (XWP) reached ca. -1 MPa. Although both...
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1. Windblown dust, an environmental problem in many disturbed arid lands, has the potential to affect the physiological performance of desert shrubs. Physiological parameters of gas exchange for three species (Larrea tridentata, Hymenoclea salsola and Atriplex canescens) were measured at a Mojave Desert site, at which both undisturbed and heavily dusted individual shrubs occurred. 2. Maximum rates of net photosynthesis (A) of dusted organs were reduced to 21% of those of control plants in resinous leaflets of Larrea, to 44% in resinous leaves and photosynthetic stems of Hymenoclea, and to 58% in non-resinous C4 leaves of Atriplex, which have vesiculated trichomes. Dusted plants of all three species showed reduced...
Turgor maintenance, solute content and recovery from water stress were examined in the drought-tolerant shrub Artemisia tridentata. Predawn water potentials of shrubs receiving supplemental water remained above ?2 MPa throughout summer, while predawn water potentials of untreated shrubs decreased to ?5 MPa. Osmotic potentials decreased in conjunction with water potentials maintaining turgor pressures above 0 MPa. The decreases in osmotic potentials were not the result of osmotic adjustment (i.e. solute accumulation). Leaf solute contents decreased during drought, but leaf water volumes decreased more than 75% from spring to summer, thereby passively concentrating solutes within the leaves. The maintenance of positive...
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Seedlings of the succulent crassulacean acid metabolism (CAM plant Agave deserti in the northwestern Sonoran Desert were found only in sheltered microhabitats, nearly all occurring under the canopy of a desert bunchgrass, Hilaria rigida. Apparently because soil surface temperatures can reach 71@?C in exposed areas, seedlings were generally located near the center or on the northern side of this nurse plant. Both species have shallow root systems, about half of the roots of H. rigida and all those for seedlings of A. deserti occurring above soil depths of 0.08 m. To examine competition for water between the nurse plant and an associated seedling, a three-dimensional model for root water uptake was developed. The...
The seasonality of Glomus fasciculatum associated with Bouteloua gracilis and Pascopyrum smithii was contrasted in the field, as well as the effects of this vesicular-arbuscular mycorrhizal (VAM) fungus on physiological parameters of these grasses in the greenhouse Arbuscule formation was earlier in P smithii, which has C3 photophysiology, than in the C1 B gracilis Soil spore densities were highest in fall samples of both grasses Both grasses exhibited lower stomatal resistance and increased photosynthesis with VAM formation, but these changes were 36% greater for B gracilis B gracilis has a greater percentage of VAM infection than P smithii in the field, but % of the root length infected in the two grasses was...


map background search result map search result map Surface Dust Impacts on Gas Exchange in Mojave Desert Shrubs Interactions Between Seedlings of Agave Deserti and the Nurse Plant Hilaria Rigida Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata Interactions Between Seedlings of Agave Deserti and the Nurse Plant Hilaria Rigida Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata Surface Dust Impacts on Gas Exchange in Mojave Desert Shrubs