LIGHT DEPENDENCE OF QUANTUM YIELDS OF PHOTOSYSTEM-II AND CO(2) FIXATION IN C(3) AND C(4) PLANTS
LIGHT DEPENDENCE OF QUANTUM YIELDS OF PHOTOSYSTEM-II AND CO(2) FIXATION IN C(3) AND C(4) PLANTS
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DOI：
10.1007/bf00016557
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发表时间：
1993-03-01
影响因子：
3.7
通讯作者：
EDWARDS, GE
中科院分区：
文献类型：
--
作者：
OBERHUBER, W;DAI, ZY;EDWARDS, GE
光系统II（PHI（II））和CO2固定的量子产率的光依赖性在C3和C4植物光呼吸是最小的大气条件下确定。通过将测量的光合作用速率除以吸收的光[A/I（a）= PHI（CO2）]来计算CO2固定的表观量子产率，并通过将估计的真实光合作用速率除以吸收的光[（A + R（L）/I（a）= PHI（CO2*）]来计算真实量子产率，其中R（L）是光中的呼吸速率。然后评价PHI（II）/PHI（CO2*）和PHI（II）/PHI（CO2）比率对光强度的依赖性。在C3和C4植物中，在相当于10-100%全日照的光强度下，PHI（II）/PHI（CO2）的比率几乎没有变化，而在较低的光强度下，该比率急剧增加。由于光合系统之间能量分配的变化或PS II活性与CO2固定之间关系的变化，呼吸损失未被考虑，因此可能发生PHI（II）/PHI（CO2）比值的变化。低光强下PS Ⅱ固定CO2的能量利用效率明显降低，可能是由于CO2的呼吸损失。使用暗呼吸作为R（L）的估计，计算的PHI（II）/PHI（CO2*）的比例几乎是恒定的，从全日照下降到全日照的约5%，这表明在不同的光强度下，CO2固定的真实速率和PS II活性之间有很强的联系。通过照射代表性C3和C4单子叶植物和双子叶植物的上下叶表面来测量光合速率和PHI（II）。与单子叶植物，光合速率和比例的PHI（II）/PHI（CO2）表现出非常相似的模式，从近轴面与远轴面，这可能是由于在解剖学上的均匀性和缺乏差异的光驯化两个表面之间的叶片。与双子叶植物，远轴面有较低的光合速率和较低的PHI（II）值比近轴面，这可能是由于在解剖学（海绵与栅栏叶肉细胞）和/或光驯化两个表面之间的差异。然而，在每一个物种的反应PHI（II）/PHI（CO2）不同的光强度是相似的两个表面之间，表明PS II活性和CO2固定之间的可比链接。
The light dependence of quantum yields of Photosystem II (PHI(II)) and of CO2 fixation were determined in C3 and C4 plants under atmospheric conditions where photorespiration was minimal. Calculations were made of the apparent quantum yield for CO2 fixation by dividing the measured rate of photosynthesis by the absorbed light [A/I(a) = PHI(CO2)] and of the true quantum yield by dividing the estimated true rate of photosynthesis by absorbed light [(A + R(L)/I(a) = PHI(CO2*)], where R(L) is the rate of respiration in the light. The dependence of the PHI(II)/PHI(CO2*) and PHI(II)/PHI(CO2) ratios on light intensity was then evaluated. In both C3 and C4 plants there was little change in the ratio of PHI(II)/PHI(CO2) at light intensities equivalent to 10-100% of full sunlight, whereas there was a dramatic increase in the ratio at lower light intensities. Changes in the ratio of PHI(II)/PHI(CO2) can occur because respiratory losses are not accounted for, due to changes in the partitioning of energy between photosystems or changes in the relationship between PS II activity and CO2 fixation. The apparent decrease in efficiency of utilization of energy derived from PS II for CO2 fixation under low light intensity may be due to respiratory loss of CO2. Using dark respiration as an estimate of R(L), the calculated PHI(II)/PHI(CO2*) ratio was nearly constant from full sunlight down to approx 5% of full sunlight, which suggests a strong linkage between the true rate of CO2 fixation and PS II activity under varying light intensity. Measurements of photosynthesis rates and PHI(II) were made by illuminating upper versus lower leaf surfaces of representative C3 and C4 monocots and dicots. With the monocots, the rate of photosynthesis and the ratio of PHI(II)/PHI(CO2) exhibited a very similar pattern with leaves illuminated from the adaxial versus the abaxial surface, which may be due to uniformity in anatomy and lack of differences in light acclimation between the two surfaces. With dicots, the abaxial surface had both lower rates of photosynthesis and lower PHI(II) values than the adaxial surface which may be due to differences in anatomy (spongy versus palisade mesophyll cells) and/or light acclimation between the two surfaces. However, in each species the response of PHI(II)/PHI(CO2) to varying light intensity was similar between the two surfaces, indicating a comparable linkage between PS II activity and CO2 fixation.