There is very little robust, experimentally based knowledge comparing drought tolerance of one legume species with another. Dehydration tolerance and plant survival of the perennial legumes white clover (Trifolium repens L., considered quite sensitive to drought) and lucerne (Medicago sativa L., considered drought tolerant) were compared in a drying cycle experiment conducted in pots in a glasshouse, with the deep rooting of lucerne constrained. White clover used more soil water, drying the pots to a final soil gravimetric water content (θ_g) of 4.7%, compared with 8.3% in lucerne pots. Rates of water use were also different: white clover used 0.47% of θ_g per day and lucerne 0.3%. The more conservative water use allowed lucerne to survive for longer into the drying cycle than white clover. Lucerne partitioned more of its total dry matter into root growth and had much higher root:shoot ratios than white clover. Leaf/stolon elongation is one of the first plant processes to cease as water deficit increases; however, elongation was greater in white clover than lucerne at the beginning of the drying cycle, and this trend continued until lower soil water contents were reached. Conversely, leaf senescence generally commenced at quite high levels of water stress and progressed more rapidly to complete senescence in white clover than in lucerne. Lucerne retained tissue relative water content at a higher level than white clover, with final minimum values of 25% and 13.6%, respectively. In lucerne, 50% mortality was observed at θ_g of 9%, compared with 6% in white clover, albeit with greater variability. In conclusion, lucerne maintained a higher relative water content than white clover even though it endured the drying cycle for longer and without access to water at depth, evidence of its superior dehydration avoidance and better adaptation to dry conditions. However, white clover was more able to extract water from surface soil layers. This study provides valuable insight into the adaptive traits of both species and identifies some traits that might be useful in the quest to improve white clover adaptation.

比较一种豆科植物物种与另一种豆科植物的耐旱性的可靠的，基于实验的知识很少。在温室温室的干燥循环试验中，比较了多年生豆科植物三叶草（Trifolium repens L.，被认为对干旱非常敏感）和卢塞恩（Medicago sativa L.，被认为是抗旱）的耐旱性和植物存活率。卢塞恩的根深蒂固。白三叶草使用了更多的土壤水，使花盆干燥至最终土壤重量水含量（_θg）为4.7％，而卢塞恩花盆为8.3％。耗水率也有所不同：白三叶草的耗水量为_θg的0.47％每天和卢塞恩0.3％。与白三叶草相比，更保守的用水方式使卢塞恩在干燥循环中的存活时间更长。卢塞恩将更多的总干物质分配到根部生长，并且比白三叶草具有更高的根：茎比率。叶片/ deficit茎的伸长是随着水分亏缺增加而停止的第一个植物过程。然而，在干燥周期开始时，白三叶草的伸长率比卢塞恩大，并且这种趋势一直持续到土壤水含量降低为止。相反，在三叶草中，叶片衰老通常始于较高水平的水分胁迫，并且比卢塞恩中的叶片衰老进展更快，以完成衰老。卢塞恩将组织的相对水含量保持在比白三叶草更高的水平，最终最小值分别为25％和13.6％。在卢塞恩，_g的含量为9％，而白三叶草为6％，尽管变异性更大。总之，尽管紫罗兰忍受了更长的干燥周期且没有深水接触，但仍保持了比白三叶草更高的相对水分含量，这证明了其出色的避免脱水性能和对干燥条件的更好适应性。但是，白三叶草更能够从表层土壤中提取水。这项研究提供了对这两个物种的适应性状的宝贵见解，并确定了一些对改善白三叶草适应性可能有用的性状。