Faculty of Agriculture, Food and Natural Resources, The University of Sydney, Private Bag 4011, Narellan NSW 2567, Australia.
Plant Cell Environ. 2011 May;34(5):792-9. doi: 10.1111/j.1365-3040.2011.02282.x. Epub 2011 Mar 15.
Leaf intrinsic water-use efficiency (WUE), the ratio of photosynthetic rate to stomatal conductance (A/g(s) ), is a key plant trait linking terrestrial carbon and water cycles. A rapid, integrative proxy for A/g(s) is of benefit to crop breeding programmes aiming to improve WUE, but also for ecologists interested in plant carbon-water balance in natural systems. We hypothesize that the carbon isotope composition of leaf-respired CO(2) (δ(13) C(Rl) ), two hours after leaves are transferred to the dark, records photosynthetic carbon isotope discrimination and so provides a proxy for A/g(s) . To test this hypothesis, δ(13) C(Rl) was measured in four barley cultivars grown in the field at two levels of water availability and compared to leaf-level gas exchange (the ratio of leaf intercellular to ambient CO(2) partial pressure, C(i) /C(a) , and A/g(s) ). Leaf-respired CO(2) was more (13) C-depleted in plants grown at higher water availability, varied between days as environmental conditions changed, and was significantly different between cultivars. A strong relationship between δ(13) C(Rl) and δ(13) C of sucrose was observed. δ(13) C(Rl) was converted into apparent photosynthetic discrimination (Δ(13) C(Rl) ) revealing strong relationships between Δ(13) C(Rl) and C(i) /C(a) and A/g(s) during the vegetative stage of growth. We therefore conclude that δ(13) C(Rl) may provide a rapid, integrative proxy for A/g(s) in barley.
叶片内在水分利用效率（WUE），即光合速率与气孔导度的比值（A/g(s)），是连接陆地碳和水循环的关键植物特性。A/g(s)的快速综合替代物对于旨在提高 WUE 的作物育种计划以及对自然系统中植物碳-水平衡感兴趣的生态学家都很有好处。我们假设，叶片暗呼吸 CO2 的碳同位素组成（δ(13) C(Rl)），在叶片转移到黑暗后两小时记录了光合作用的碳同位素分馏，因此提供了 A/g(s)的替代物。为了验证这一假设，我们在两个水分可利用水平下，对四个大麦品种进行了田间生长实验，测量了 δ(13) C(Rl)，并将其与叶片水平的气体交换（叶片胞间与环境 CO2 分压的比值，C(i) /C(a)，和 A/g(s)）进行了比较。在水分供应较高的条件下，生长的植物中叶片暗呼吸 CO2 的（13）C 更贫化，随着环境条件的变化，它在不同的天数之间发生变化，并且在品种之间存在显著差异。δ(13) C(Rl)与蔗糖的δ(13) C 之间存在很强的相关性。将 δ(13) C(Rl)转换为表观光合分馏（Δ(13) C(Rl)），揭示了在生长的营养阶段，Δ(13) C(Rl)与 C(i) /C(a)和 A/g(s)之间存在很强的关系。因此，我们得出结论，δ(13) C(Rl)可能为大麦中 A/g(s)提供快速综合的替代物。
