Charles F. Kettering Research Laboratory, Yellow Springs, Ohio 45387.
Plant Physiol. 1971 May;47(5):600-5. doi: 10.1104/pp.47.5.600.
Isolated mesophyll cells and bundle sheath cells of Digitaria sanguinalis were used to study the light-absorbing pigments and electron transport reactions of a plant which possesses the C(4)-dicarboxylic acid cycle of photosynthesis. Absorption spectra and chlorophyll determinations are presented showing that mesophyll cells have a chlorophyll a-b ratio of about 3.0 and bundle sheath cells have a chlorophyll a-b ratio of about 4.5. The absorption spectrum of bundle sheath cells has a greater absorption in the 700 nm region at liquid nitrogen temperature, and there is a relatively greater amount of a pigment absorbing at 670 nm in the bundle sheath cells compared to the mesophyll cells. Fluorescence emission spectra, at liquid nitrogen temperature, of mesophyll cells have a fluorescence 730 nm-685 nm ratio of about 0.82 and bundle sheath cells have a ratio of about 2.84. The reversible light-induced absorption change in the region of P(700) absorption is similar in both cell types but bundle sheath cells exhibit about twice as much total P(700) change as mesophyll cells on a total chlorophyll basis. The delayed light emission of bundle sheath cells is about one-half that of mesophyll cells. Both mesophyll cells and bundle sheath cells evolve oxygen in the presence of Hill oxidants with the mesophyll cells exhibiting about twice the activity of bundle sheath cells, and both activities are inhibited by 1 muM 3-(3,4-dichlorophenyl)-1, 1-dimethylurea. Ferredoxin nicotinamide adenine dinucleotide phosphate reductase is present in both cells although it is about 3- or 4-fold higher in mesophyll cells than in bundle sheath cells. Glyceraldehyde 3-P dehydrogenases, both nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate, are equally distributed in the two cell types on a chlorophyll basis. Malic enzyme is localized in the bundle sheath cells.We interpret the data as evidence for the presence of a complete chloroplast electron transport system from oxygen evolution to pyridine nucleotide reduction in both mesophyll and bundle sheath cells. However, there is a quantitative difference in the distribution of photosystem I and photosystem II components in the two photosynthetic cells with about a 3-fold higher photosystem I-II ratio in the bundle sheath cells than in the mesophyll cells. A scheme is proposed to accommodate photosynthetic CO(2) fixation and electron transport activities in the mesophyll cells via a beta-carboxylation and in the bundle sheath cells via carboxylation of ribulose-1, 5-diphosphate.
使用分离的狗牙根叶片的叶肉细胞和维管束鞘细胞来研究具有光合作用 C(4)-二羧酸循环的植物的光吸收色素和电子传递反应。呈现吸收光谱和叶绿素测定结果表明，叶肉细胞的叶绿素 a-b 比值约为 3.0，维管束鞘细胞的叶绿素 a-b 比值约为 4.5。维管束鞘细胞的吸收光谱在液氮温度下在 700nm 区域具有更大的吸收，并且与叶肉细胞相比，维管束鞘细胞中吸收在 670nm 的色素的量相对较大。叶肉细胞的液氮温度下的荧光发射光谱，其荧光 730nm-685nm 比值约为 0.82，维管束鞘细胞的比值约为 2.84。在两种细胞类型中，可逆的光诱导吸收变化在 P(700)吸收区域相似，但基于总叶绿素，维管束鞘细胞的总 P(700)变化是叶肉细胞的两倍。维管束鞘细胞的延迟荧光发射约为叶肉细胞的一半。在 Hill 氧化剂存在的情况下，叶肉细胞和维管束鞘细胞都产生氧气，叶肉细胞的活性约为维管束鞘细胞的两倍，并且这两种活性都被 1μm 3-(3,4-二氯苯基)-1,1-二甲基脲抑制。尽管在叶肉细胞中 ferredoxin NADP 还原酶的含量是维管束鞘细胞的 3-或 4 倍，但它存在于这两种细胞中。甘油醛 3-P 脱氢酶，无论是 NAD 还是 NADP，在两种细胞类型中的分布都是基于叶绿素相等的。苹果酸酶定位于维管束鞘细胞中。我们将这些数据解释为证据，表明在叶肉细胞和维管束鞘细胞中都存在完整的叶绿体电子传递系统，从氧气产生到吡啶核苷酸还原。然而，在这两种光合作用细胞中，光系统 I 和光系统 II 成分的分布存在定量差异，维管束鞘细胞的光系统 I-II 比值比叶肉细胞高约 3 倍。提出了一个方案，以适应叶肉细胞中通过β羧化作用和维管束鞘细胞中通过核酮糖-1,5-二磷酸羧化作用进行的光合作用 CO2 固定和电子传递活动。
