Valladares F, Sánchez-Gómez D
Instituto de Recursos Naturales, CCMA-CSIC, Serrano 115, 28006 Madrid, Spain.
Plant Biol (Stuttg). 2006 Sep;8(5):688-97. doi: 10.1055/s-2006-924107. Epub 2006 Jun 13.
Species differ regarding their drought tolerance and individuals of a given species can modify their morphology and physiology in response to drought. However, since evolutionary and ecological selective pressures differ, individual and interspecific responses to drought might not match. We determined summer survival and a number of ecophysiological variables in two factorial experiments with seedlings of eleven tree species present in Mediterranean ecosystems, grown under slowly imposed water stress and control conditions. Plants experiencing drought exhibited reduced growth, low specific leaf area, chlorophyll content, and photosynthetic rate when compared to the controls, and species-specific drought tolerance was associated with an analogous set of trait values. However, while species with high leaf area ratio and shoot-root ratio exhibited greater drought tolerance, drought induced the reversed response within species. Contrary to expectations, water use efficiency was lower in drought-tolerant species and decreased in water-stressed individuals compared to the control plants. There was a distinctive phylogenetic signal in the functional grouping of species, with oaks, pines, and other genera being clearly different from each other in their drought tolerance and in their functional responses to drought. However, all relationships between ecophysiological variables and drought tolerance were significant after accounting for phylogenetic effects, with the exception of the relationship between drought tolerance and photochemical efficiency. Our results show that drought tolerance is not achieved by a single combination of trait values, and that even though evolutionary processes and individual responses tend to render similar results in terms of functional traits associated with drought, they do not necessarily match.
不同物种的耐旱能力存在差异，同一物种的个体也会因干旱而改变其形态和生理特征。然而，由于进化和生态选择压力不同，个体和种间对干旱的反应可能并不一致。我们在两个析因实验中，测定了地中海生态系统中11种树木幼苗在缓慢施加水分胁迫和对照条件下的夏季存活率以及一些生态生理变量。与对照相比，经历干旱的植物生长减缓，比叶面积、叶绿素含量和光合速率降低，物种特异性耐旱性与一组类似的性状值相关。然而，虽然叶面积比和茎根比高的物种表现出更强的耐旱性，但干旱在物种内部却引发了相反的反应。与预期相反，耐旱物种的水分利用效率较低，与对照植物相比，水分胁迫个体的水分利用效率下降。物种的功能分组存在明显的系统发育信号，栎属、松属和其他属在耐旱性及其对干旱的功能反应方面明显不同。然而，在考虑系统发育效应后，除了耐旱性与光化学效率之间的关系外，所有生态生理变量与耐旱性之间的关系均具有显著性。我们的结果表明，耐旱性并非由单一的性状值组合实现，而且尽管进化过程和个体反应在与干旱相关的功能性状方面往往产生相似的结果，但它们不一定匹配。
