02239nas a2200217 4500008004100000245015000041210006900191300001200260490001200272520147500284100002301759700002201782700002401804700002301828700002001851700002001871700001501891700002501906700002301931856006701954 2018 eng d00aDrought tolerance in ecotypes of big bluestem (Andropogon gerardii) relates to above-ground surface area: Results from a common garden experiment0 aDrought tolerance in ecotypes of big bluestem Andropogon gerardi a52 - 600 v246-2473 a

Big bluestem (Andropogon gerardii Vitman) is a dominant tallgrass species that has a wide range in North America with numerous genetically-distinct ecotypes, each adapted to conditions in their native habitat. In an evolutionary context, it was hypothesized that drought adaptation in A. gerardii would relate to plant surface area, where drought-adapted ecotypes were expected to be short with narrow leaves, thin stems, and few leaves per tiller. In the context of individual plants acclimating to reduced rainfall, rainout shelters were hypothesized to cause morphological reductions in surface area of individual plants. Morphological measurements were taken from four genetically-distinct ecotypes of A. gerardii across a precipitation gradient ranging from 500 to 900 mm rain per year at three common garden sites in Colby, Hays, and Manhattan, Kansas, USA. Evolutionary responses to drier soils in A. gerardii resulted in reduction of evaporative surface area from leaves, as drought-adapted plants had fewer and smaller leaves. The most mesic ecotype of A. gerardii had the highest maximum leaf width, stem diameter, and leaf count across sites. There were few effects of environment on morphology in A. gerardii with reduced rainfall, however, indicating genetics plays a more prominent role than environment to influence morphology. We conclude that increased drought tolerance is related to an evolutionary reduction in evaporative surface area.

1 aKramer, Diedre, L.1 aMaricle, Keri, L.1 aHilt, Christina, J.1 aMartin, Nicole, M.1 aUrban, Adam, D.1 aSmart, Cera, M.1 aBaer, S.G.1 aJohnson, Loretta, C.1 aMaricle, Brian, R. uhttps://linkinghub.elsevier.com/retrieve/pii/S036725301830246902494nas a2200181 4500008004100000245009100041210006900132300001400201490000800215520189200223100002102115700002402136700002502160700002202185700001502207700002302222856006702245 2018 eng d00aGenetic and environmental influences on stomates of big bluestem (Andropogon gerardii)0 aGenetic and environmental influences on stomates of big bluestem a477 - 4870 v1553 a

Big bluestem (Andropogon gerardii) is a dominant C4 prairie grass that has wide distribution and several genetically distinct ecotypes. Many of the ecotypic adaptations are related to water availability in the native environment. Stomates facilitate photosynthetic gas exchange and regulate water loss from the plant. As such, stomatal size and density represent possible adaptations to conserve water. We hypothesized drought-tolerant ecotypes of big bluestem would have fewer or smaller stomates compared to more mesic ecotypes. Five ecotypes of big bluestem were planted in four common gardens from western Kansas to southern Illinois, USA to determine genetic and environmental influences on stomates. Leaves of all ecotypes of A. gerardii were largely hypostomatous and genetics was a greater influence than environment for stomatal size and density. The drought-tolerant Sand bluestem had larger stomates on abaxial surfaces of leaves, but a lower density compared to most other ecotypes. The most mesic Illinois ecotype and the Kaw cultivar had the greatest density of stomates on abaxial surfaces of leaves. Sand Bluestem had a greater density of stomates on adaxial surfaces of leaves compared to all other ecotypes. Gas exchange measures followed patterns of stomate distribution, where abaxial CO2 uptake rates were greater than adaxial CO2 uptake rates, although differences between leaf surfaces was more pronounced in stomatal density than in CO2 uptake. There were minor differences in size and density of stomates among sites that corresponded with precipitation, although these differences were minor, illustrating the genetic underpinnings of stomates in big bluestem. There is a genetic predisposition for drought-tolerant ecotypes to have fewer stomates, illustrating an evolutionary adaptation to drought tolerance in an important prairie species.
 

1 aVarvel, Nick, A.1 aHilt, Christina, J.1 aJohnson, Loretta, C.1 aGalliart, Matthew1 aBaer, S.G.1 aMaricle, Brian, R. uhttps://linkinghub.elsevier.com/retrieve/pii/S0098847218300807