Polley H W, Johnson H B, Mayeux H S, Tischler C R, Brown D A
Grassland, Soil and Water Research Laboratory, USDA, Agricultural Research Service, Temple, Texas 76502, USA.
Tree Physiol. 1996 Oct;16(10):817-23. doi: 10.1093/treephys/16.10.817.
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 CO(2) concentrations of 370 (ambient), 710, and 1050 micro mol mol(-1). Because elevated CO(2) decreases stomatal conductance, the number of seedlings per container in the elevated CO(2) treatments was increased to ensure that soil water content was depleted at similar rates in all treatments. Seedlings grown at elevated CO(2) had a greater root biomass and a higher ratio of lateral root to total root biomass than those grown at ambient CO(2) concentration; however, these seedlings also shed more leaves and retained smaller leaves. These changes, together with a reduced transpiration/leaf area ratio at elevated CO(2), may have contributed to a slight increase in xylem pressure potentials of seedlings in the 1050 micro mol mol(-1) CO(2) treatment during the first 37 days of growth (0.26 to 0.40 MPa). Osmotic potential was not affected by CO(2) treatment. Increasing the CO(2) concentration to 710 and 1050 micro mol 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 CO(2) concentration may increase abundance of P. glandulosa on grasslands where low water availability limits its establishment.
低水分可利用性会减少某些草原上入侵灌木牧豆树属植物的定植。在370（环境浓度）、710和1050微摩尔/摩尔（-1）的二氧化碳浓度下生长的腺叶牧豆树（蜜豆树）幼苗，测定了其水分亏缺存活率以及可能有助于推迟或耐受植物脱水的性状。由于二氧化碳浓度升高会降低气孔导度，因此在高二氧化碳处理中每个容器的幼苗数量增加，以确保所有处理中土壤水分含量以相似的速率耗尽。与在环境二氧化碳浓度下生长的幼苗相比，在高二氧化碳浓度下生长的幼苗具有更大的根生物量以及更高的侧根与总根生物量之比；然而，这些幼苗也脱落了更多的叶子且保留的叶子更小。这些变化，再加上高二氧化碳浓度下蒸腾作用/叶面积比的降低，可能导致了在生长的前37天中，处于1050微摩尔/摩尔（-1）二氧化碳处理的幼苗木质部压力势略有增加（从0.26兆帕增加到0.40兆帕）。渗透势不受二氧化碳处理的影响。将二氧化碳浓度提高到710和1050微摩尔/摩尔（-1），使水分 withheld 65天的幼苗存活率提高了一倍多。在土壤水分含量最低的幼苗中，二氧化碳富集显著将存活率从0%提高到了约40%。通过提高干旱条件下的幼苗存活率，大气二氧化碳浓度升高可能会增加在低水分可利用性限制其定植的草原上腺叶牧豆树属植物的丰度。
