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Genetic Variability for Stomatal Conductance in Pima Cotton and its Relation to Improvements of Heat Adaptation

John W. Radin, Zhenmin Lu, Richard G. Percy and Eduardo Zeiger
Proceedings of the National Academy of Sciences of the United States of America
Vol. 91, No. 15 (Jul. 19, 1994), pp. 7217-7221
Stable URL: http://www.jstor.org/stable/2365251
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Genetic Variability for Stomatal Conductance in Pima Cotton and its Relation to Improvements of Heat Adaptation
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Abstract

Responses of stomata to environment have been intensively studied, but little is known of genetic effects on stomatal conductance or their consequences. In Pima cotton (Gossypium barbadense L.), a crop that is bred for irrigated production in very hot environments, stomatal conductance varies genetically over a wide range and has increased with each release of new higher-yielding cultivars. A cross between heat-adapted (high-yielding) and unadapted genotypes produced F2 progeny cosegregating for stomatal conductance and leaf temperature. Within segregating populations in the field, conductance was negatively correlated with foliar temperature because of evaporative cooling. Plants were selected from the F2 generation specifically and solely for differing stomatal conductance. Among F3 and F4 populations derived from these selections, conductance and leaf cooling were significantly correlated with fruiting prolificacy during the hottest period of the year and with yield. Conductance was not associated with other factors that might have affected yield potential (single-leaf photosynthetic rate, leaf water potential). As breeders have increased the yield of this crop, genetic variability for conductance has allowed inadvertent selection for "heat avoidance" (evaporative cooling) in a hot environment.

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