Valladares Fernando, Martinez-Ferri Elsa, Balaguer Luis, Perez-Corona Esther, Manrique Esteban
1 Centro de Ciencias Medioambientales, C. S. I. C. Serrano 115, E-28006 Madrid, Spain.
New Phytol. 2000 Oct;148(1):79-91. doi: 10.1046/j.1469-8137.2000.00737.x.
We have explored leaf-level plastic response to light and nutrients of Quercus ilex and Q. coccifera, two closely related Mediterranean evergreen sclerophylls, in a factorial experiment with seedlings. Leaf phenotypic plasticity, assessed by a relative index (PI = (maximum value - minimum)/maximum) in combination with the significance of the difference among means, was studied in 37 morphological and physiological variables. Light had significant effects on most variables relating to photosynthetic pigments, chlorophyll fluorescence and gas exchange, whereas nutrient treatment had a significant effect in only 10% of the variables. Chlorophyll content was higher in the shade whereas carotenoid content and nonphotochemical quenching increased with light. Nutrient limitations increased the xanthophyll-cycle pool but only at high light intensities, and the same interaction between light and nutrients was observed for lutein. Predawn photochemical efficiency of PSII was not affected by either light or nutrients, although midday photochemical efficiency of PSII was lower at high light intensities. Photosynthetic light compensation point and dark respiration on an area basis decreased with light, but photosynthetic capacity on a dry mass basis and photochemical quenching were higher in low light, which translated into a higher nitrogen use efficiency in the shade. We expected Q. ilex, the species of the widest ecological distribution, to be more plastic than Q. coccifera, but differences were minor: Q. ilex exhibited a significant response to light in 13% more of the variables than Q. coccifera, but mean PI was very similar in the two species. Both species tolerated full sunlight and moderate shade, but exhibited a reduced capacity to enhance photosynthetic utilization of high irradiance. When compared with evergreen shrubs from the tropical rainforest, leaf responsiveness of the two evergreen oaks was low. We suggest that the low leaf-level responsiveness found here is part of a conservative resource use strategy, which seems to be adaptive for evergreen woody plants in Mediterranean-type ecosystems.
我们通过对幼苗进行析因实验，探究了两种近缘的地中海常绿硬叶植物冬青栎和胭脂虫栎叶片水平对光照和养分的可塑性响应。通过相对指数（PI =（最大值 - 最小值）/最大值）结合均值差异的显著性来评估叶片表型可塑性，研究了37个形态和生理变量。光照对大多数与光合色素、叶绿素荧光和气体交换相关的变量有显著影响，而养分处理仅对10%的变量有显著影响。叶绿素含量在遮荫条件下较高，而类胡萝卜素含量和非光化学猝灭随光照增加。养分限制增加了叶黄素循环库，但仅在高光强下如此，并且叶黄素也观察到光照和养分之间的相同相互作用。PSII的黎明前光化学效率不受光照或养分的影响，尽管PSII的午间光化学效率在高光强下较低。基于面积的光合光补偿点和暗呼吸随光照降低，但基于干质量的光合能力和光化学猝灭在低光下较高，这导致在遮荫条件下氮利用效率更高。我们预期生态分布最广的冬青栎比胭脂虫栎具有更高的可塑性，但差异较小：冬青栎对光照有显著响应的变量比胭脂虫栎多13%，但两个物种的平均PI非常相似。两个物种都能耐受全日照和适度遮荫，但增强对高辐照光合利用的能力有所降低。与热带雨林的常绿灌木相比，这两种常绿栎树的叶片响应性较低。我们认为这里发现的低叶片水平响应性是保守资源利用策略的一部分，这似乎是地中海型生态系统中常绿木本植物的一种适应性特征。
