摘要
在相同的叶绿素浓度下，叶绿素缺乏的大麦突变体的叶绿体在450～480nm和600～640nm波长范围的光吸收值比野生型略高，而在400～440nm和700～740nm波长范围的光吸收值明显高于野生型；突变体叶片和叶绿体的低温（77K）荧光发射强度较低，而两个光系低温荧光产量的比值（r685／F735）较高；失去Mg2+后，突变体和野生型的F685／F735和Fv／Fm均降低，但突变体的降低幅度较小；突变体的叶绿体中基粒片层数目较少、长度较短，而间质片层较长。这些结果表明，大麦突变体PSⅡ向PSⅠ的激发能转移较少是其PSⅡ光化学效率较高的重要原因。
A comparative study of barleychloroplast ultrastructure, absorption spectrum characteristics and low temperaturechlorophyll fluorescence was made on the mutunt rePOrted in a previous paper (Tan et al.1996) and itS wild-type to explore further thecause of the higher photochemical efficiencyof PS Ⅱ in the mutant.As compared with the wild-type, thelight absorption of chloroplasts in mutant barley was slightly hisher within 450-480 urnand 600 - 640 urn but much higher within400-440 urn and 700-740 urn in the caseof equal amount of chlorophyll. The mutunthad a lower chlorophyll fluorescence yield atlow temperature (77K), but a higher ratio offluorescence yield of PS Ⅱ to that of PS Ⅰ,F685/F735. The effects of Mg2+ depletion,which could lower the F685/F735 ratio andthe photochemical efficiency of PS Ⅱ, Fv/Fm, were weaker in the mutunt than in thewild-type. Marked changes in chloroplast ultrastructure, such as fewer grana stacks andlonger stromal lamellae, were observed in themutant.These results support the suggestion presented in the previous peper that higher photo-chemical efficiency of PSⅡ in the mutantmay be caused by the lesser excitation energytransfer from PS Ⅱ to PS Ⅰ.
关键词
化学效率
叶绿素缺乏
突变体
大麦
光合系Ⅱ
PS Ⅱ photochemical efficiency, excitation energy transfer, chlorophyll fluorescence,chlorophyll-deficient mutant, barley
