Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia.
Protoplasma. 2010 Sep;245(1-4):49-73. doi: 10.1007/s00709-010-0135-7. Epub 2010 May 7.
The localization of the key photoreductive and oxidative processes and some stress-protective reactions within leaves of mesophytic C(3) plants were investigated. The role of light in determining the profile of Rubisco, glutamate oxaloacetate transaminase, catalase, fumarase, and cytochrome-c-oxidase across spinach leaves was examined by exposing leaves to illumination on either the adaxial or abaxial leaf surfaces. Oxygen evolution in fresh paradermal leaf sections and CO(2) gas exchange in whole leaves under adaxial or abaxial illumination was also examined. The results showed that the palisade mesophyll is responsible for the midday depression of photosynthesis in spinach leaves. The photosynthetic apparatus was more sensitive to the light environment than the respiratory apparatus. Additionally, examination of the paradermal leaf sections by optical microscopy allowed us to describe two new types of parenchyma in spinach-pirum mesophyll and pillow spongy mesophyll. A hypothesis that oxaloacetate may protect the upper leaf tissue from the destructive influence of active oxygen is presented. The application of mathematical modeling shows that the pattern of enzymatic distribution across leaves abides by the principle of maximal ecological utility. Light regulation of carbon metabolism across leaves is discussed.
研究了中生型 C3 植物叶片中关键光还原和光氧化过程以及一些应激保护反应的定位。通过将叶片暴露于叶片的腹面或背面进行光照，研究了光在确定菠菜叶片中 Rubisco、谷氨酸草酰乙酸转氨酶、过氧化氢酶、延胡索酸酶和细胞色素 c 氧化酶的分布中的作用。还检查了新鲜表皮叶段中的氧气释放和整个叶片在腹面或背面光照下的 CO2 气体交换。结果表明，栅栏叶肉是导致菠菜叶片光合作用中午下降的原因。光合器官比呼吸器官对光照环境更敏感。此外，通过光学显微镜检查表皮叶段，我们能够描述菠菜中的两种新类型的组织-扁果组织和枕状海绵组织。提出了草酰乙酸可能保护上叶组织免受活性氧破坏性影响的假说。数学模型的应用表明，酶在叶片中的分布模式符合最大生态效用的原则。讨论了叶片间碳代谢的光调节。
