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Variability in stomatal characteristics of C4 grasses native to the Nebraska Sandhills.
MOSER, LOWELL1, AWADA, TALA1, SCHACHT, WALTER1, REECE, PATRICK1, 1
ABSTRACT- We examined intra- and interspecific variability in stomatal characteristics and drought tolerance in sand bluestem (Andropogon hallii), little bluestem (Schizachyrium scoparium), prairie sandreed (Calamovilfa longifolia) and switchgrass (Panicum virgatum). Ramets were collected during the dormant season across an aridity gradient (ranging from 560 mm in the east to 430 mm in the west in average annual precipitation) in the Sandhills of Nebraska. Plants were grown under greenhouse conditions. There was not significant intraspecific variability in stomatal characteristics across the gradient, but there was a significant interspecific difference. Leaves of switchgrass and prairie sandreed were amphistomatic (stomata on both leaf surfaces) while leaves of little bluestem and sand bluestem were hypostomatic (stomata on the lower leaf surface). In the absence of drought, stomatal conductance (gs) was 17 to 31% higher in little bluestem than in other species. Differences among species in gs were mainly found at the beginning of drought and disappeared as the dry-down progressed. There was a positive relationship between stomatal density and conductance in all species except prairie sandreed. Prairie sandreed maintained 45% of the initial absolute water content of its leaves after 17 days of dry-down, possibly due to the tight rolling of its leaves, compared to 21% for sand bluestem, 18% for switchgrass, and 7% for little bluestem. Stomatal traits of local populations of the grasses studied did not vary across the wide range of environmental conditions represented in the Nebraska Sandhills.
KEY WORDS: Ecotypic variability, drought, C4 grasses , Sandhills of Nebraska