Leaf Functional Anatomy in Relation to Photosynthesis
Leaf Functional Anatomy in Relation to Photosynthesis
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DOI：
10.1104/pp.110.165472
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发表时间：
2011-01-01
期刊：
影响因子：
7.4
通讯作者：
Niinemets, Uelo
中科院分区：
文献类型：
--
作者：
Terashima, Ichiro;Hanba, Yuko T.;Niinemets, Uelo
Rubisco是一种分子量约为550kd的大型酶。二氧化碳固定的最大速度(即核酮糖1 5 5-bisphosphate, [RuBP]羧化作用)在二氧化碳饱和只有15到30摩尔二氧化碳摩尔21二磷酸核酮糖羧化酶蛋白s 21 25 C .亲和力二氧化碳也低,公里,Kc, 25 C在缺乏氧气与二氧化碳浓度与空气水平衡包含39 Pa二氧化碳(大约390毫升L 21), 13毫米。此外,RuBP羧化作用是由RuBP竞争性抑制氧化,这是能量消耗过程的第一步，光呼吸。当叶绿体基质中CO2浓度较低时，羧化速率降低，氧合速率增加。在这种条件下，光能和其他资源，包括氮和水，都被浪费了，最终导致植物的适应性下降。根据这些数据，我们可以认为叶片的结构特征有助于维持叶绿体基质中的高浓度二氧化碳，这可能是在进化过程中选择的。在这篇更新中，我们关注影响叶绿体基质中CO2浓度的关键结构特征。首先，我们分析了CO2从气孔下腔向叶绿体基质扩散的导度（叶肉导度[gm]，也称为内部导度）。由于低gm限制了光合作用，因此应最大限度地增加叶肉暴露于细胞间隙的表面积（Smes，单位叶面积暴露于细胞间隙的叶肉表面积），以增加CO2溶解的面积和CO2扩散的有效途径，从而增加光合作用。其次，我们分析叶片内的光环境，因为为了最大限度地发挥光合作用，光应该被传递到叶片中的所有叶绿体，沿着细胞壁分布。关于叶片内的光环境，我们也指出了一些
Rubisco is a large enzyme with a molecular mass of approximately 550 kD. The maximum rate of CO2 fixation (ie ribulose-1, 5-bisphosphate [RuBP] carboxylation) at CO2 saturation is only 15 to 30 mol CO2 mol 21 Rubisco protein s 21 at 25 C. Affinity to CO2 is also low, and the Km, Kc, at 25 C in the absence of oxygen is comparable to the CO2 concentration in water equilibrated with air containing 39 Pa CO2 (approximately 390 mL L 21), 13 mM. Moreover, RuBP carboxylation is competitively inhibited by RuBP oxygenation, which is the primary step of the energy-wasting process, photorespiration. If the CO2 concentration in the chloroplast stroma is low, the carboxylation rate will decrease while the oxygenation rate will increase. Under such conditions, light energy and other resources, including nitrogen and water, are all wasted, eventually leading to a decrement of fitness of the plants. From these data, we may consider that structural features of the leaf contributing to the maintenance of the high CO2 concentration in the chloroplast stroma may have been selected during evolution.In this Update, we focus on the key structural features that affect CO2 concentration in the chloroplast stroma. First, we analyze the conductance for CO2 diffusion from the substomatal cavity to the chloroplast stroma (mesophyll conductance [gm], also called internal conductance). Because the low gm limits photosynthesis, the mesophyll surface area exposed to the intercellular spaces (Smes, mesophyll surface area exposed to intercellular spaces per unit leaf area) should be maximized to increase the area for CO2 dissolution and the effective pathway for CO2 diffusion, and thereby photosynthesis. Second, we analyze the light environment within a leaf, because, for maximizing photosynthesis, light should be delivered to all the chloroplasts in the leaf, distributing along the cell walls. In relation to the light environment within a leaf, we also point out some