叶绿素缺乏的大麦突变体的光合作用和叶绿素荧光

Leaf Photosynthesis and Chlorophyll Fluorescence in a Chlorophyll-deficient Mutant of Barley

和早熟３号大麦（野生型）（ＤＧ）相比，黄化大麦（突变体）（ＬＧ）叶片Ｃｈｌ含量低，而Ｃｈｌａ／ｂ较高；光合速率低，表现量子效率低，而饱和光强较高，气孔导度较高；荧光参数Ｆｏ低，而ＰＳⅡ的光化学效率（Ｆｖ／Ｆｍ）以及Ｔ１／２、Ｆｍ／Ｆｏ、Φｅ均高。以单位叶绿素计算，黄化大麦的ＰＳⅡ电子传递活性和全链电子传递活性较高，而ＰＳⅠ电子传递活性较低。推测黄化大麦ＰＳⅡ的光化学效率增高可能是由于其ＰＳⅡ向ＰＳⅠ传递的激发能较少，是对Ｃｈｌ含量低的一种补偿。

A comparative study of barley leaf photosynthesis and chlorophyll fluorescence was made between a Chl-deficient mutant (with light green leaf, LG) and its wild-type (dark green leaf, DG) in order to further explore the regulatory mechanism of photosynthesis.As compared with DG, LG had a lower net photosynthesis rate (Pn) and apparent quantum yield (AQY) (Table 1 ), but a higher stomatal conductance (Table 2),indicating that the lower Pn of LG may result from lower Chl (Chl a and Chl b) content,but not from lower stomatal conductance.PS Ⅱ photochemical efficiency (Fv/Fm) was about 10% higher in LG than in DG (Table 3),which is different from the chlorophyll b-less mutant of barley reported by Leverenz et al.(1992 ). Furthermore, LG had higher Chl a/Chl b ratio, a relative larger PQ pool, as indicated by fluorescence parameter T1/2, and a higher PS Ⅱ electron transport (H2O→DMBQ) rate as well as whole chain electron transport (H2O→MV) rate, but a lower PS Ⅰelectron transport (DCPIP→MV) rate when expressed in unit Chl (Table 4 ).From these results, it is deduced that the higher PS Ⅱ photochemical efficiency in LG results from the less excittation energy transfer from PS Ⅱ to PS Ⅰ,which may compensate the lower light harvest capacity due to Chl deficiency.High light (about 1 700 μmol photons m-1 s-1 ) treatment resulted in a smaller decrease of Fv/Fm in LG than in DG (Table 5 ), indicating that the mutant is less sensitive to photoinhibition conditions, which is contrary to that of chlorophyll-deficient mutant of soybean reported by Xu et al. (1993).