Grodzinski B, Woodrow L, Leonardos E D, Dixon M, Tsujita M J
Department of Horticultural Science, University of Guelph, Canada.
Adv Space Res. 1996;18(4-5):203-11. doi: 10.1016/0273-1177(95)00879-j.
When higher plants are exposed to elevated levels of CO2 for both short- and long-term periods photosynthetic C-gain and photoassimilate export from leaves are generally increased. Water use efficiency is increased on a leaf area basis. During long-term exposures, photosynthesis rates on leaf and whole plants bases are altered in a species specific manner. The most common pattern in C3 plants is an enhanced rate of whole plant photosynthesis in a well irradiated canopy. Nevertheless, in some herbaceous species prolonged exposure to high CO2 results in remobilization of nitrogenous reserves (i.e., leaf protein degradation) and reduced rates of mature leaf photosynthesis when assayed at ambient CO2 and O2 levels. Both short- and long-term exposures to those CO2 levels (i.e., 100 to 2,000 microliter l-1) which modify photosynthesis and export, also modify both endogenous ethylene gas (C2H4) release, and substrate, 1-aminocyclopropane-1-carboxylic acid (ACC), saturated C2H4 release rates from irradiated leaves. Photosynthetically active canopy leaves contribute most of the C2H4 released from the canopy. Prolonged growth at high CO2 results in a persistent increase in the rate of endogenous C2H4 release from leaves which can, only in part, be attributed to the increase of the endogenous pools of C2H4 pathway intermediates (e.g., methionine, M-ACC, and ACC). The capacity for increasing the rate of C2H4 release in response to short-term exposures to varying CO2 levels does not decline after prolonged growth at high CO2. When leaves, whole plants, and model canopies of tomato plants are exposed to exogenous C2H4 a reduction in the rate of photosynthesis can, in each case, be attributed to the classical effects of C2H4 on plant development and morphology. The effect of C2H4 on CO2 gas exchange of plant canopies is shown to be dependent on the canopy leaf area index.
当高等植物短期和长期暴露于高浓度二氧化碳时，叶片的光合碳同化和光合产物输出通常会增加。基于叶面积的水分利用效率会提高。在长期暴露过程中，叶片和整株植物的光合速率会以物种特异性的方式发生改变。C3植物中最常见的模式是在光照良好的冠层中整株植物的光合速率提高。然而，在一些草本物种中，长时间暴露于高浓度二氧化碳会导致含氮储备的重新分配（即叶片蛋白质降解），并且在环境二氧化碳和氧气水平下测定时，成熟叶片的光合速率会降低。短期和长期暴露于那些改变光合作用和输出的二氧化碳水平（即100至2000微升/升），也会改变内源性乙烯气体（C2H4）的释放以及底物1-氨基环丙烷-1-羧酸（ACC）从受照射叶片的饱和C2H4释放速率。光合活性冠层叶片贡献了冠层释放的大部分C2H4。在高浓度二氧化碳下长期生长会导致叶片内源性C2H4释放速率持续增加，这只能部分归因于C2H4途径中间产物（例如蛋氨酸、M-ACC和ACC）内源性池的增加。在高浓度二氧化碳下长期生长后，响应短期暴露于不同二氧化碳水平而增加C2H4释放速率的能力不会下降。当番茄植株的叶片、整株植物和模型冠层暴露于外源C2H4时，在每种情况下，光合作用速率的降低都可归因于C2H4对植物发育和形态的经典影响。结果表明，C2H4对植物冠层二氧化碳气体交换的影响取决于冠层叶面积指数。
