Carbon dioxide enrichment improves growth, water relations and survival of droughted honey mesquite (Prosopis glandulosa) seedlings
1996
Polley, H.W. | Johnson, H.B. | Mayeux, H.S. | Tischler, C.R. | Brown, DA.
Low water availability reduces the establishment of the invasive shrub Prosopis on some grasslands. Water deficit survival and traits that may contribute to the postponement or tolerance of plant dehydration were measured on seedlings of P. glandulosa Torr. var. glandulosa (honey mesquite) grown at CO2 concentrations of 370 (ambient), 710, and 1050 micromole mol-1. Because elevated CO2 decreases stomatal conductance, the number of seedlings per container in the elevated CO2 treatments was increased to ensure that soil water content was depleted at similar rates in all treatments. Seedlings grown at elevated CO2 had a greater root biomass and a higher ratio of lateral root to total root biomass than those grown at ambient CO2 concentration; however, these seedlings also shed more leaves and retained smaller leaves. These changes, together with a reduced transpiration/leaf area ratio at elevated CO2, may have contributed to a slight increase in xylem pressure potentials of seedlings in the 1050 micromole mol-1 CO2 treatment during the first 37 days of growth (0.26 to 0.40 MPa). Osmotic potential was not affected by CO2 treatment. Increasing the CO2 concentration to 710 and 1050 micromole mol-1 more than doubled the percentage survival of seedlings from which water was withheld for 65 days. Carbon dioxide enrichment significantly increased survival from 0% to about 40% among seedlings that experienced the lowest soil water content. By increasing seedling survival of drought, rising atmospheric CO2 concentration may increase abundance of P. glandulosa on grasslands where low water availability limits its establishment.
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