Crassulacean acid metabolism-cycling in Euphorbia milii.
Crassulacean acid metabolism-cycling in Euphorbia milii.
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DOI：
10.1093/aobpla/plt014
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发表时间：
2013
期刊：
影响因子：
2.9
通讯作者：
Herrera A
中科院分区：
文献类型：
--
作者：
Herrera A
首次报道了小米大戟的光合特性。CAM循环的发生被证明是一种节水机制。这是一个详细的和新的报告，这种CAM模式的属，这是丰富的组成CAM和C4物种。解剖学证据的可能运作的CO2集中机制周围的维管束，C2路线，提供。这些发现对于我们理解CAM在该属中的进化具有重要意义。景天科酸代谢（CAM）发生在许多大戟科，特别是大戟属，C3和C4物种以及。与我们的知识的CAM在这一属的进化的目的，本研究探讨了可能发生的CAM在大戟，一个物种的叶片肉质和耐旱性暗示这一碳固定途径。叶片解剖结构包括一个栅栏薄壁组织，海绵薄壁组织和一个维管束鞘与叶绿体，这表明可能的功能C2光合作用。没有证据表明，夜间CO2固定在植物的E。milii无论是浇水或干旱;浇水的植物有低的夜间呼吸速率（R）。12天不浇水后，光合速率（PN）下降85%，夜间R几乎为零.在浇水的植物中，夜间H+积累（ΔH+）为18 ± 2（对应于苹果酸）和18 ± 4（柠檬酸）μmol H+（g鲜重）−1。通过酸合成的呼吸CO2再循环有助于夜间节水2%和86%，分别在浇水的植物和植物在干旱下。碳同位素组成（δ 13 C）：叶为−25.2 ± 0.7 ‰，茎为−24.7 ± 0.1 ‰。在E. milii，具有统计学显著的ΔH+，无夜间CO2吸收，δ 13 C值介于C3和组成型CAM植物之间; ΔH+明显归因于苹果酸和柠檬酸。结果表明，苹果酸的日积累是部分夜间呼吸CO2再循环的结果，这有助于解释叶片δ 13 C中间值的出现。小米大戟可以被认为是CAM循环的物种。本文还讨论了在大肠杆菌中进行CAM循环的意义。关键在于节约用水，而不是获取碳。C2光合作用的可能发生值得研究。
Photosynthetic characteristics of Euphorbia milii are reported for the first time. The occurrence of CAM-cycling is shown to serve as a mechanism of water conservation. This is a detailed and novel report of such CAM mode in the genus, which is abundant in constitutive CAM and C4 species. Anatomical evidence for the possible operation of a CO2-concentrating mechanism around the vascular bundle, the C2 route, is provided. Findings are important for our understanding of evolution of CAM in the genus. Crassulacean acid metabolism (CAM) occurs in many Euphorbiaceae, particularly Euphorbia, a genus with C3 and C4 species as well. With the aim of contributing to our knowledge of the evolution of CAM in this genus, this study examined the possible occurrence of CAM in Euphorbia milii, a species with leaf succulence and drought tolerance suggestive of this carbon fixation pathway. Leaf anatomy consisted of a palisade parenchyma, a spongy parenchyma and a bundle sheath with chloroplasts, which indicates the possible functioning of C2 photosynthesis. No evidence of nocturnal CO2 fixation was found in plants of E. milii either watered or under drought; watered plants had a low nocturnal respiration rate (R). After 12 days without watering, the photosynthetic rate (PN) decreased 85 % and nocturnal R was nearly zero. Nocturnal H+ accumulation (ΔH+) in watered plants was 18 ± 2 (corresponding to malate) and 18 ± 4 (citrate) μmol H+ (g fresh mass)−1. Respiratory CO2 recycling through acid synthesis contributed to a night-time water saving of 2 and 86 % in watered plants and plants under drought, respectively. Carbon isotopic composition (δ13C) was −25.2 ± 0.7 ‰ in leaves and −24.7 ± 0.1 ‰ in stems. Evidence was found for the operation of weak CAM in E. milii, with statistically significant ΔH+, no nocturnal CO2 uptake and values of δ13C intermediate between C3 and constitutive CAM plants; ΔH+ was apparently attributable to both malate and citrate. The results suggest that daily malate accumulation results from recycling of part of the nocturnal respiratory CO2, which helps explain the occurrence of an intermediate value of leaf δ13C. Euphorbia milii can be considered as a CAM-cycling species. The significance of the operation of CAM-cycling in E. milii lies in water conservation, rather than carbon acquisition. The possible occurrence of C2 photosynthesis merits research.
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影响因子：
7.4
作者：
Cushman, JC
通讯作者：
Cushman, JC
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