Manetas Yiannis, Petropoulou Yiola, Psaras George K, Drinia Antonia
Department of Biology, Laboratory of Plant Physiology, Section of Plant Biology, University of Patras, Patras 265 00, Greece. Corresponding author; e-mail:
Department of Biology, Laboratory of Plant Physiology, Section of Plant Biology, University of Patras, Patras 265 00, Greece.
Funct Plant Biol. 2003 Mar;30(3):265-270. doi: 10.1071/FP02226.
Young leaves in some plants are transiently red due to the presence of anthocyanins, which disappear upon maturation. We investigated the hypothesis that light attenuation by anthocyanins may lead to a shade acclimation of the photosynthetic machinery in red leaves. We took advantage of the intra-species variation in anthocyanin levels of young, exposed leaves of Quercus coccifera. Thus, photosynthetic and photoprotective characteristics were compared in young green and red leaves of the same age, sampled from the corresponding phenotypes occupying the same habitat. Red leaves displayed several shade attributes like thinner laminae, lower Chl a/b ratios and lower levels of the xanthophyll cycle components and β-carotene. In addition, although both leaf kinds had the same area based levels of chlorophylls, these pigments were excluded from the sub-epidermic anthocyanic cell layers, leading to a further reduction of effective mesophyll thickness and an increase in chlorophyll density. Accordingly, red leaves had higher absolute chlorophyll fluorescence signals. In spite of these apparent shade characters, red leaves were less prone to photoinhibition under mild laboratory conditions and displayed slightly but significantly higher PS II photochemical efficiencies at pre-dawn in the field. No differences in all the above measured parameters were found in mature green leaves of the two phenotypes. The results confirm the light acclimation hypothesis and are also compatible with a photoprotective function of anthocyanins.
一些植物的幼叶因含有花青素而短暂呈现红色，花青素在叶片成熟时会消失。我们研究了这样一种假说：花青素造成的光衰减可能会使红叶中的光合机构适应遮荫环境。我们利用了欧洲栓皮栎幼嫩、暴露在外的叶片中花青素含量的种内差异。因此，对从占据相同生境的相应表型中采集的同龄幼嫩绿叶和红叶的光合及光保护特性进行了比较。红叶呈现出几种遮荫特征，如叶片较薄、叶绿素a/b比值较低、叶黄素循环组分和β-胡萝卜素含量较低。此外，尽管两种叶片基于面积的叶绿素水平相同，但这些色素被排除在表皮下含花青素的细胞层之外，导致有效叶肉厚度进一步减小，叶绿素密度增加。因此，红叶具有更高的绝对叶绿素荧光信号。尽管有这些明显的遮荫特征，但在温和的实验室条件下，红叶更不容易受到光抑制，并且在田间黎明前显示出略高但显著更高的PS II光化学效率。在两种表型的成熟绿叶中，未发现上述所有测量参数存在差异。这些结果证实了光适应假说，也与花青素的光保护功能相符。
