Martin B, Ruiz-Torres N A
Department of Agronomy, Oklahoma State University, Stillwater, Oklahoma 74078-0507.
Plant Physiol. 1992 Oct;100(2):733-9. doi: 10.1104/pp.100.2.733.
It is of theoretical as well as practical interest to identify the components of the photosynthetic machinery that govern variability in photosynthesis rate (A) and water-use efficiency (WUE), and to define the extent by which the component processes limit A and WUE during developing water-deficit stress. For that purpose, leaf exchange of CO(2) and H(2)O was determined in two growth-chamber-grown wheat cultivars (Triticum aestivum L. cv TAM W-101 and cv Sturdy), and the capacity of A was determined and broken down into carboxylation efficiency (c.e.), light- and CO(2)-saturated A, and stomatal conductance (g(s)) components. The limitations on A measured at ambient CO(2) concentration (A(350)) were estimated. No cultivar difference was observed when A(350) was plotted versus leaf water potential (Psi(w)). Light- and CO(2)-saturated A, c.e., and g(s) decreased with decreasing leaf Psi(w), but of the corresponding photosynthesis limitations only those caused by insufficient c.e. and g(s) increased. Thus, reduced stomatal aperture and Calvin cycle activity, but not electron transport/photophosphorylation, appeared to be major reasons for drought stress-induced inhibition of A(350). WUE measured as A(350)/g(s) first increased with stomatal closure down to a g(s) of about 0.25 mol H(2)O m(-2) s(-1) (Psi(w) = -1.6 MPa). However, it was predicted that A(350)/g(s) would decrease with more severe stress due to inhibition of c.e.
确定光合机构中控制光合速率（A）和水分利用效率（WUE）变异性的组成部分，并确定在发育中的水分亏缺胁迫期间这些组成过程限制A和WUE的程度，这在理论和实践上都具有重要意义。为此，测定了在两个生长箱中种植的小麦品种（普通小麦品种TAM W - 101和Sturdy）叶片的CO₂和H₂O交换，并测定了A的能力，并将其分解为羧化效率（c.e.）、光和CO₂饱和的A以及气孔导度（g(s)）组成部分。估计了在环境CO₂浓度（A(350)）下测量的对A的限制。当绘制A(350)与叶片水势（Ψ(w)）的关系图时，未观察到品种差异。光和CO₂饱和的A、c.e.和g(s)随叶片Ψ(w)的降低而降低，但在相应的光合作用限制中，只有那些由c.e.和g(s)不足引起的限制增加。因此，气孔孔径减小和卡尔文循环活性降低，而不是电子传递/光合磷酸化，似乎是干旱胁迫诱导抑制A(350)的主要原因。以A(350)/g(s)衡量的WUE最初随着气孔关闭增加，直到g(s)约为0.25 mol H₂O m⁻² s⁻¹（Ψ(w) = -1.6 MPa）。然而，据预测，由于c.e.受到抑制，A(350)/g(s)在更严重的胁迫下会降低。
