QUANTUM YIELDS OF PHOTOSYSTEM-II ELECTRON-TRANSPORT AND CARBON-DIOXIDE FIXATION IN C4-PLANTS
QUANTUM YIELDS OF PHOTOSYSTEM-II ELECTRON-TRANSPORT AND CARBON-DIOXIDE FIXATION IN C4-PLANTS
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DOI：
10.1071/pp9900579
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发表时间：
1990-01-01
期刊：
影响因子：
--
通讯作者：
EDWARDS, GE
中科院分区：
文献类型：
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作者：
KRALL, JP;EDWARDS, GE
在21%和2%O2条件下，在C4植物的三个亚组[玉米、大黍、黍]的代表性物种中，测定了光系统II非循环电子传递的量子产率（由叶绿素a荧光测定）和CO2合成（NADP-苹果酸酶、NAD-苹果酸酶和PEP-羧激酶），以及一系列胞间CO2浓度（Ci）。在所有三个C4亚组中，CO2同化率在整个Ci范围内（高达500 . mu.bar）与O2浓度无关。PS II电子传递的量子产率是相似的，或仅略大，在21%对25 O2在所有Ci值。与此相反，在C3种小麦有一个大的O2依赖增加PS II量子产率在低CO2，这反映了高水平的光呼吸。在C4植物中，PS II电子传递的量子产率与CO2固定的量子产率的关系是线性的，这表明PS II吸收的能量的光化学利用与C4植物中的CO2固定紧密相关。这种关系是几乎相同的，在所有三个亚组，并允许估计的光合速率的C4植物PS II光化学效率的测量的基础上。结果表明，在C4植物的光还原O2和光呼吸是低的，即使在非常有限的CO2浓度。
The quantum yields of non-cyclic electron transport from photosystem II (determined from chlorophyll a fluorescence) and carbon dioxide assmilation were measured in vivo in representative species of the three subgroups of C4 plants [Zea mays, Panicum maximum, P. miliaceum] (NADP-malic enzyme, NAD-malic enzyme and PEP-carboxykinase) over a series of intercellular CO2 concentrations (Ci) at both 21% and 2% O2. The CO2 assimilation rate was independent of O2 concentration over the entire range of Ci (up to 500 .mu.bar) in all three C4 subgroups. The quantum yield of PS II electron transport was similar, or only slightly greater, in 21% v. 25 O2 at all Ci values. In contrast, in the C3 species wheat there was a large O2 dependent increase in PS II quantum yield at low CO2, which reflects a high level of photorespiration. In the C4 plants, the relationship of the quantum yield of PS II electron transport to the quantum yield of CO2 fixation is linear suggesting that photochemical use of energy absorbed by PS II is tightly linked to CO2 fixation in C4 plants. This relationship is nearly identical in all three subgroups and may allow estimates of photosynthetic rates of C4 plants based on measurements of PS II photochemical efficiency. The results suggest that in C4 plants both the photoreduction of O2 and photorespiration are low, even at very limiting co2 concentrations.