title: Inflorescences contribute more than rosettes to lifetime carbon gain in Arabidopsis thaliana (Brassicaceae).
abstract: A metamorphosis from rosette to inflorescence in many annuals shifts photosynthetic tissue from a two-dimensional array in the soil boundary layer during cool months to a three-dimensional structure in the troposphere as spring progresses. We propose that this shift allows escape from both self-shading and an increasingly stressful boundary layer microclimate, permitting continued increases in growth. As a first step in exploring this hypothesis, we compared the lifetime C gain, water loss, and instantaneous water use efficiency (WUE) of five Arabidopsis thaliana genotypes by measuring gas exchange across the life cycle. On average, the inflorescence contributed 55% (± 5% SE) of lifetime C gain, but only 25% of lifetime water loss. Mean inflorescence WUE was nearly fourfold that of the rosette. The inflorescence continued to fix C after rosette senescence. The percentage inflorescence: total C gain varied among genotypes, from 36% to 93%. Genotypes differed in WUE for both structures. We suggest that local climates may have selected for divergence in these traits. For many annuals and winter annuals, understanding C and water budgets and their evolution must include measures of both rosette and inflorescence gas exchange.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, 162B Crawford Hall, 4249 Fifth Avenue, Pittsburgh, Pennsylvania 15260.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Earley
authors.forename: Bronson
authors.initials: B
authors.lastname: Ingland
authors.forename: Jacob
authors.initials: J
authors.lastname: Winkler
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Tonsor