C3-CAM中间型植物冰叶日中花叶片中脉和叶脉间叶片的光合作用相关特性
Photosynthesis-related characteristics of the midrib and the interveinal lamina in leaves of the C3-CAM intermediate plant Mesembryanthemum crystallinum.
作者信息
Kuźniak Elżbieta, Kornas Andrzej, Kaźmierczak Andrzej, Rozpądek Piotr, Nosek Michał, Kocurek Maciej, Zellnig Günther, Müller Maria, Miszalski Zbigniew
机构信息
Department of Plant Physiology and Biochemistry, Faculty of Biology and Environmental Protection, University of Lodz, Banacha 12/16, 90-237 Łódź, Poland.
Institute of Biology, Pedagogical University, Podchorążych 2, 30-084 Kraków, Poland.
出版信息
Ann Bot. 2016 Jun;117(7):1141-51. doi: 10.1093/aob/mcw049. Epub 2016 Apr 18.
BACKGROUND AND AIMS
Leaf veins are usually encircled by specialized bundle sheath cells. In C4 plants, they play an important role in CO2 assimilation, and the photosynthetic activity is compartmentalized between the mesophyll and the bundle sheath. In C3 and CAM (Crassulacean acid metabolism) plants, the photosynthetic activity is generally attributed to the leaf mesophyll cells, and the vascular parenchymal cells are rarely considered for their role in photosynthesis. Recent studies demonstrate that enzymes required for C4 photosynthesis are also active in the veins of C3 plants, and their vascular system contains photosynthetically competent parenchyma cells. However, our understanding of photosynthesis in veins of C3 and CAM plants still remains insufficient. Here spatial analysis of photosynthesis-related properties were applied to the midrib and the interveinal lamina cells in leaves of Mesembryanthemum crystallinum, a C3-CAM intermediate plant.
METHODS
The midrib anatomy as well as chloroplast structure and chlorophyll fluorescence, diurnal gas exchange profiles, the immunoblot patterns of PEPC (phosphoenolpyruvate carboxylase) and RubisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase), H2O2 localization and antioxidant enzyme activities were compared in the midrib and in the interveinal mesophyll cells in leaves of C3 and CAM plants.
KEY RESULTS
Leaf midribs were structurally competent to perform photosynthesis in C3 and CAM plants. The midrib chloroplasts resembled those in the bundle sheath cells of C4 plants and were characterized by limited photosynthetic activity.
CONCLUSIONS
The metabolic roles of midrib chloroplasts differ in C3 and CAM plants. It is suggested that in leaves of C3 plants the midrib chloroplasts could be involved in the supply of CO2 for carboxylation, and in CAM plants they could provide malate to different metabolic processes and mediate H2O2 signalling.
背景与目的
叶脉通常被特化的维管束鞘细胞环绕。在C4植物中，它们在二氧化碳同化过程中发挥重要作用，光合作用活性在叶肉细胞和维管束鞘细胞之间进行区室化。在C3和景天酸代谢（CAM）植物中，光合作用活性通常归因于叶肉细胞，维管束薄壁细胞在光合作用中的作用很少被考虑。最近的研究表明，C4光合作用所需的酶在C3植物的叶脉中也具有活性，并且它们的维管系统包含具有光合能力的薄壁细胞。然而，我们对C3和CAM植物叶脉光合作用的理解仍然不足。在此，将光合作用相关特性的空间分析应用于C3-CAM中间植物冰叶日中花叶片的中脉和脉间叶肉细胞。
方法
比较了C3和CAM植物叶片中脉和脉间叶肉细胞的中脉解剖结构、叶绿体结构和叶绿素荧光、昼夜气体交换曲线、磷酸烯醇式丙酮酸羧化酶（PEPC）和核酮糖-1,5-二磷酸羧化酶/加氧酶（RubisCO）的免疫印迹模式、过氧化氢定位和抗氧化酶活性。
主要结果
在C3和CAM植物中，叶片中脉在结构上具备进行光合作用的能力。中脉叶绿体类似于C4植物维管束鞘细胞中的叶绿体，其特点是光合活性有限。
结论
C3和CAM植物中脉叶绿体的代谢作用不同。有人提出，在C3植物叶片中，中脉叶绿体可能参与为羧化作用提供二氧化碳，而在CAM植物中它们可以为不同的代谢过程提供苹果酸并介导过氧化氢信号传导。
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