Department of Biological Sciences, University of Pittsburgh, 162B Crawford Hall, 4249 Fifth Avenue, Pittsburgh, Pennsylvania 15260.
Am J Bot. 2009 Apr;96(4):786-92. doi: 10.3732/ajb.0800149. Epub 2009 Mar 20.
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.
在许多一年生植物中，从花冠状结构到花序的转变将光合作用组织从凉爽月份土壤边界层中的二维排列转移到春季进展时的对流层中的三维结构。我们提出，这种转变可以避免自遮蔽和边界层微气候日益紧张的情况，从而允许持续增长。作为探索这一假设的第一步，我们通过测量整个生命周期的气体交换，比较了五个拟南芥（Arabidopsis thaliana）基因型的终生 C 增益、水分损失和瞬时水分利用效率（WUE）。平均而言，花序贡献了 55%（± 5% SE）的终生 C 增益，但仅贡献了 25%的终生水分损失。花序的平均 WUE 几乎是花冠状结构的四倍。花序在花冠状结构衰老后继续固定 C。花冠状结构与总 C 增益的比例在基因型之间有所不同，从 36%到 93%不等。两种结构的 WUE 在基因型之间也存在差异。我们认为，局部气候可能已经选择了这些性状的差异。对于许多一年生植物和冬季一年生植物，理解 C 和水预算及其演变必须包括对花冠状结构和花序气体交换的测量。
