Bolger T P, Turner N C
CSIRO Plant Industry, Centre for Mediterranean Agricultural Research, PO Wembley, WA 6014, Australia, , , , , , AU.
Oecologia. 1998 Jun;115(1-2):32-38. doi: 10.1007/s004420050488.
Attempts to improve water use efficiency in regions with Mediterranean climates generally focus on increasing plant transpiration relative to evaporation from the soil and increasing transpiration efficiency. Our aim was to determine if transpiration efficiency differs among key species occurring in annual pastures in southern Australia. Two glasshouse experiments were conducted with three key pasture species, subterranean clover (Trifolium subterraneum L.), capeweed [Arctotheca calendula (L.) Levyns] and annual ryegrass (Lolium rigidum Gaudin), and wheat (Triticum aestivum L.). Transpiration efficiency was assessed at the levels of␣whole-plant biomass and water use (W), leaf gas exchange measurements of the ratio of CO assimilation to leaf conductance to water vapour (A/g), and carbon isotope discrimination (Δ) in leaf tissue. In addition, Δ was measured on shoots of the three pasture species growing together in the field. In the glasshouse studies, annual ryegrass had a consistently higher transpiration efficiency than subterranean clover or capeweed by all methods of measurement. Subterranean clover and capeweed had similar transpiration efficiencies by all three methods of measurement. Wheat had W values similar to ryegrass but A/g and Δ values similar to subterranean clover or capeweed. The high W of annual ryegrass seems to be related to a conservative leaf gas exchange behaviour, with lower assimilation and conductance but higher A/g than for the other species. In contrast to the glasshouse results, the three pasture species had similar Δ values when growing together in mixed-species swards in the field. Reasons for these differing responses between glasshouse and field-grown plants are discussed in terms of the implications for improving the transpiration efficiency of mixed-species annual pasture communities in the field.
在地中海气候地区，提高水分利用效率的尝试通常集中在相对于土壤蒸发增加植物蒸腾作用以及提高蒸腾效率上。我们的目的是确定澳大利亚南部一年生牧场中主要物种的蒸腾效率是否存在差异。我们用三种主要的牧场物种——地下三叶草（Trifolium subterraneum L.）、海角草[Arctotheca calendula (L.) Levyns]和一年生黑麦草（Lolium rigidum Gaudin）以及小麦（Triticum aestivum L.）进行了两项温室试验。在整株生物量和水分利用（W）水平、叶片气体交换中二氧化碳同化与叶片水汽导度之比（A/g）以及叶片组织中的碳同位素分馏（Δ）等方面评估了蒸腾效率。此外，还对田间一起生长的三种牧场物种的地上部分进行了Δ测量。在温室研究中，通过所有测量方法，一年生黑麦草的蒸腾效率始终高于地下三叶草或海角草。通过所有三种测量方法，地下三叶草和海角草的蒸腾效率相似。小麦的W值与黑麦草相似，但A/g和Δ值与地下三叶草或海角草相似。一年生黑麦草的高W值似乎与保守的叶片气体交换行为有关，其同化和导度较低，但A/g高于其他物种。与温室结果相反，这三种牧场物种在田间混播草地中一起生长时，Δ值相似。本文根据对提高田间混播一年生牧场群落蒸腾效率的影响，讨论了温室植物和田间生长植物之间这些不同反应的原因。
