木本植物阳生和阴生叶片叶绿体O2和NO2-光还原作用

THE O2 AND NO2- PHOTOREDUCTION IN CHLOROPLASTS OF SUN AND SHADE LEAVES OF WOODY PLANTS

摘要:

在有PCR和PCO环活性抑制剂甘油醛和光合磷酸化解偶联剂NH₄CL存在下，比较了生长于3种 光环境的乔木黧蒴和灌木九节幼苗阳生和阴生叶片叶绿体的O₂和NO₂^-光还原速率。全自然光下两种 植物阳生叶片的叶绿体O₂的光还原速率最高，占总光合电子传递活性的66％－68％，NO₂^-光还原速率 也有类似趋势占总电子传递的11％－15％左右。36％和16％自然光下阴生叶片O₂和NO₂^-光还原 速率及O₂光还原电子传递的比例显著降低，但NO₂^-光还原电子传递的比例不受影响。与NO₂^-光还原 相关的叶片NiR和NR活性及NiR/NR活性比也因叶片接受光强度大小而异，随光强减弱，黧蒴的NiR活性降低，九节的NR活性增高，但黧蒴的NR活性和九节的NiR活性变化未达差异显著性。

Abstract:

O₂ and NO₂^- photoreduction in chloroplasts isolated from the leaves of Castanopsis fissa (tree) and Psychotria rubra (shrub) seedlings grown under three light intensities were compared in the presence of glyceraldehyde (an inhibitor of PCR and PCO cycle activity) and NH₄Cl (uncoupler of photophosphorylation). The highest rate of O₂ photoreduction (Mehler reaction) was observed in chloroplasts from full sun-exposed leaves of both plants,which was 66%-68% of total electron transport. NO₂^- photoreduction showed a similar trend， but it was only l1％-15％ of total electron transport activity．Shade leaves exposed to 36％ and 16％ of full sun light significantly decreased the photoreduction rates of 0₂ and NO₂^- and the percentage of 0₂ photoreduction to total electron transport，but had no effect on the percentage of electron transport partitioning to NO₂^- photoreduction． The activities of nitrite reductase(NiR)，nitrate reductase (NR)in leaves and the ratio of NiR／NR activity were also afFected by light intensity．As the light intensity was reduced，NiR activity decreased in C. fissa，and NR activity increased in P．rubra， whereas the changes in NR activity in C. fissa or NiR activity in P. rubra were not significant．The ratio of NiR/NR activity in two sun leaves reached more than 3，and it was just 1.7—2.2 in shade 1eaves．