WATER RELATIONS AND GROWTH CHARACTERISTICS OF PROSOPIS GLANDULOSA VAR. TORREYANA IN A SIMULATED PHREATOPHYTIC ENVIRONMENT |
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| Authors: | Erik T Nilsen R A Virginia W M Jarrell |
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| Institution: | 1. Biology Department, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, 24061;2. Biology Department and Systems Ecology Research Group, San Diego State University, San Diego, California, 92182;3. Department of Soils and Environmental Sciences, University of California, Riverside, California, 92521 |
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| Abstract: | Recent studies of Prosopis glandulosa have demonstrated a unique system of a deeply rooted species with significant water stress tolerance. Several growth and developmental characteristics have been correlated with water stress and nitrogen availability during field studies. Here we present a lab experiment in which a phreatophytic regime is simulated and the availability of nitrogen and water are varied. Increased ground water salinity caused lower plant water potentials and greater osmotic adjustment without significant increases in leaf Na+ concentrations. Leaf conductance was higher in the higher salinity treatments. Low water potential was also associated with reduced leaf size, reduced leaf area per plant and increased root to shoot ratio. Specific leaf weight and the transpiration ratio were unaffected by the low water potentials induced by increased salinity. Increasing nitrogen availability caused increased growth rates but did not influence water use efficiency. Net assimilation rates increased with increasing nitrogen availability but relative growth rates were more dependent on overall plant size than treatment conditions. The responses of P. glandulosa to the simulated phreatophytic environment were similar to those predicted by field measurements. |
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