Fernández R J, Reynolds J F
Department of Botany, Duke University, Durham, NC 27708, USA, , , , , , US.
Oecologia. 2000 Apr;123(1):90-98. doi: 10.1007/s004420050993.
Eight perennial C-4 grasses from the Jornada del Muerto Basin in southern New Mexico show five-fold differences in relative growth rates under well- watered conditions (RGR). In a controlled environment, we tested the hypothesis that there is an inverse relationship (trade-off) between RGR and the capacity of these species to tolerate drought. We examined both physiological (gas exchange) and morphological (biomass allocation, leaf properties) determinants of growth for these eight species under three steady-state drought treatments (none=control, moderate, and severe). When well watered, the grasses exhibited a large interspecific variation in growth, which was reflected in order-of-magnitude biomass differences after 5 weeks. The species had similar gas-exchange characteristics, but differed in all the measured allocation and morphological characteristics, namely tiller mass and number, root:shoot ratio, dry-matter content, and specific leaf area (SLA). Drought affected tillering, morphology, and allocation, and reduced growth by 50 and 68% (moderate and severe drought, respectively) compared to the well-watered controls. With the exception of SLA, none of these variables showed a significant species-by-treatment interaction. We calculated three indices of drought tolerance, defined as the ratio in final biomass between all the possible "dry"/"wet" treatment pairs: severe/moderate, moderate/control, and severe/control. We found no significant correlation between these drought tolerance indices, on the one hand, and three indices of growth potential (greenhouse RGR, final biomass in the control treatment, and final:initial biomass ratio in controls), on the other. Based on these controlled-environment results, we hypothesize that the commonly reported correlation between plant growth potential and drought tolerance in the field may in some cases be explained by differential effects of plants on soil-water content rather than by differences in species responses to drought.
来自新墨西哥州南部乔纳达德尔穆埃托盆地的8种多年生C4草本植物在水分充足的条件下，相对生长率（RGR）呈现出5倍的差异。在可控环境中，我们检验了以下假设：这些物种的RGR与耐旱能力之间存在负相关关系（权衡）。我们在三种稳态干旱处理（无干旱=对照、中度干旱和重度干旱）下，研究了这8种植物生长的生理（气体交换）和形态（生物量分配、叶片特性）决定因素。水分充足时，这些草本植物在生长方面表现出较大的种间差异，5周后生物量差异达数量级。这些物种具有相似的气体交换特征，但在所有测量的分配和形态特征上存在差异，即分蘖质量和数量、根冠比、干物质含量和比叶面积（SLA）。干旱影响分蘖、形态和分配，与水分充足的对照相比，生长分别降低了50%和68%（中度和重度干旱）。除SLA外，这些变量均未显示出显著的物种×处理交互作用。我们计算了三个耐旱性指标，定义为所有可能的“干旱”/“湿润”处理对之间最终生物量的比值：重度/中度、中度/对照和重度/对照。一方面，我们发现这些耐旱性指标与三个生长潜力指标（温室RGR、对照处理中的最终生物量以及对照中的最终：初始生物量比值）之间没有显著相关性。基于这些可控环境结果，我们推测，田间常见的植物生长潜力与耐旱性之间的相关性在某些情况下，可能是由植物对土壤水分含量的不同影响而非物种对干旱的反应差异所解释。
