Holloway-Phillips Meisha-Marika, Brodribb Timothy J
Tasmanian Institute of Agricultural Research, University of Tasmania, Private Bag 98, Hobart, Tas. 7001, Australia.
School of Plant Science, University of Tasmania, Private Bag 55, Hobart, Tas. 7001, Australia.
Funct Plant Biol. 2011 Jul;38(7):594-605. doi: 10.1071/FP11029.
Plant traits that improve crop water use efficiency are highly sought after but difficult to isolate. Here, we examine the integrated function of xylem and stomata in closely related forage grasses to determine whether quantitative differences in water transport properties could be used to predict plant performance under limited water conditions. Cultivars of two forage grass species with different drought tolerance ratings, Lolium multiflorum Lam. and Festuca arundinacea Schreb., were assessed for maximum hydraulic conductivity (Kmax), vulnerability of xylem to hydraulic dysfunction (P50) and stomatal sensitivity to leaf water potential. Species-specific differences were observed in several of these traits, and their effect on whole-plant performance was examined under well-watered and restricted watering conditions. It was shown that although P50 was comparable between species, for F. arundinacea cultivars, there was greater hydraulic risk associated with reduced stomatal sensitivity to leaf hydration. In contrast, L. multiflorum cultivars expressed a higher capacity for water transport, but more conservative stomatal regulation. Despite different susceptibilities to leaf damage observed during acute drought, under the sustained moderate drought treatment, the two strategies were balanced in terms of water conservation and hydraulic utilisation, resulting in similar dry matter production. Characterisation of water use patterns according to the key hydraulic parameters is discussed in terms of implications to yield across different environmental scenarios as well as the applicability of water transport related traits to breeding programs.
提高作物水分利用效率的植物性状备受关注，但难以分离。在此，我们研究了亲缘关系相近的饲草中木质部和气孔的综合功能，以确定水分运输特性的定量差异是否可用于预测有限水分条件下的植物表现。对两种具有不同耐旱等级的饲草品种，即多花黑麦草（Lolium multiflorum Lam.）和高羊茅（Festuca arundinacea Schreb.），评估了最大水力传导率（Kmax）、木质部对水力功能障碍的脆弱性（P50）以及气孔对叶片水势的敏感性。在这些性状中的几个方面观察到了种间差异，并在充分浇水和限制浇水条件下研究了它们对整株植物表现的影响。结果表明，尽管种间P50相当，但对于高羊茅品种，气孔对叶片水合作用敏感性降低会带来更大的水力风险。相比之下，多花黑麦草品种表现出更高的水分运输能力，但气孔调节更为保守。尽管在急性干旱期间观察到对叶片损伤的易感性不同，但在持续中度干旱处理下，这两种策略在水分保持和水力利用方面达到了平衡，导致干物质产量相似。根据关键水力参数对水分利用模式进行了表征，并讨论了其对不同环境情景下产量的影响以及水分运输相关性状在育种计划中的适用性。
