Blackman Chris J, Aspinwall Michael J, Tissue David T, Rymer Paul D
Hawkesbury Institute for the Environment, Western Sydney University, Hawkesbury Campus, Locked Bag 1797, Penrith, NSW 2751, Australia.
Tree Physiol. 2017 May 1;37(5):583-592. doi: 10.1093/treephys/tpx005.
The ability of plants to maintain an intact water transport system in leaves under drought conditions is intimately linked to survival and can been be seen as adaptive in shaping species climatic limits. Large differences in leaf hydraulic vulnerability to drought are known among species from contrasting climates, yet whether this trait varies among populations within a single species and, furthermore, whether it is altered by changes in growth conditions, remain unclear. We examined intraspecific variation in both leaf water transport capacity (Kleaf) and leaf hydraulic vulnerability to drought (P50leaf) among eight populations of Corymbia calophylla (R. Br.) K.D. Hill & L.A.S. Johnson (Myrtaceae) from both cool and warm climatic regions grown reciprocally under two temperature treatments representing the cool and warm edge of the species distribution. Kleaf did not vary between cool and warm-climate populations, nor was it affected by variable growth temperature. In contrast, population origin and growth temperature independently altered P50leaf. Using data pooled across growth temperatures, cool-climate populations showed significantly higher leaf hydraulic vulnerability (P50leaf = -3.55 ± 0.18 MPa) than warm-climate populations (P50leaf = -3.78 ± 0.08 MPa). Across populations, P50leaf decreased as population home-climate temperature increased, but was unrelated to rainfall and aridity. For populations from both cool and warm climatic regions, P50leaf was lower under the warmer growth conditions. These results provide evidence of trait plasticity in leaf hydraulic vulnerability to drought in response to variable growth temperature. Furthermore, they suggest that climate, and in particular temperature, may be a strong selective force in shaping intraspecific variation in leaf hydraulic vulnerability to drought.
植物在干旱条件下维持叶片完整水分运输系统的能力与生存密切相关，可视为塑造物种气候极限的适应性表现。已知来自不同气候的物种在叶片对干旱的水力脆弱性方面存在很大差异，但该性状在单一物种的不同种群间是否变化，以及是否会因生长条件的改变而变化，仍不清楚。我们研究了来自凉爽和温暖气候区域的8个红胶桉（Corymbia calophylla (R. Br.) K.D. Hill & L.A.S. Johnson，桃金娘科）种群在两种温度处理（分别代表该物种分布的凉爽和温暖边缘）下相互种植时，叶片水分运输能力（Kleaf）和叶片对干旱的水力脆弱性（P50leaf）的种内变异。Kleaf在凉爽和温暖气候种群之间没有差异，也不受生长温度变化的影响。相比之下，种群来源和生长温度独立改变了P50leaf。综合不同生长温度的数据来看，凉爽气候种群的叶片水力脆弱性（P50leaf = -3.55 ± 0.18 MPa）显著高于温暖气候种群（P50leaf = -3.78 ± 0.08 MPa）。在所有种群中，P50leaf随着种群原生气候温度的升高而降低，但与降雨量和干旱程度无关。对于来自凉爽和温暖气候区域的种群，在较温暖的生长条件下P50leaf更低。这些结果提供了叶片对干旱的水力脆弱性性状可塑性的证据，以响应可变的生长温度。此外，它们表明气候，尤其是温度，可能是塑造叶片对干旱的水力脆弱性种内变异的强大选择力量。
