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Responses of C 4 Grasses to Atmospheric CO 2 Enrichment. II. Effect of Water Stress 1

1985; Wiley; Volume: 25; Issue: 3 Linguagem: Inglês

10.2135/cropsci1985.0011183x002500030024x

1435-0653

Nasser Sionit, David T. Patterson,

Plant Water Relations and Carbon Dynamics

Changes in leaf water potential, photosynthesis, and stomatal conductance in response to atmospheric CO s enrichment at two watering regimes were studied in :Four species of C 4 grasses: Echinochloa crusgalli, Digitaria sanguinalis, Eleusine indica , and Setaria faberi . Plants were grown in controlled environment chambers at 350 and 675 μmol mol ‐1 CO 2 with 1000 μmol m ‐2 s‐ 1 photosynthetic photon tux density (PPFD). One group plants of each of the COs concentrations was subjected to water stress by withholding irrigation for 10 days starting 21 days after planting. Water potentials of the leaves of plants grown at 350 #tool mol ‐1 CO 2 declined more rapidly and reached lower values at the end of the stress period than the water potential of those grown at 675 μmol mol ‐1 CO 2 . High COs‐grown plants maintained higher turgor pressures than low CO 2 ‐grown plants. All plants had lower rates of photosynthesis during water stress compared to non‐stressed conditions. However, the net photosynthetic rates of the plants grown at high CO 2 concentration did not decline as rapidly as the rates of plants grown at low CO 2 when subjected to water stress. The maintenance of turgor along with CO 2 enrichment during water stress development in plant leaves may be responsible for the higher rates of net photosynthesis observed in high CO 2 ‐grown plants compared to those in low CO 2 ‐grown plants.