【摘要】 水稻5叶期,用低钾(1ppm)处理使净光合率和气孔导度明显下降,虽然单位叶面积的叶绿素含量差异不大,但离体叶绿体的光合磷酸化和电子传递活力明显降低。外源钾可分别提高两种钾处理的水稻离体叶绿体的电子传递活力。初步认为低钾使PSⅠ、PSⅡ及其氧化还原两侧的活力下降。更多还原

【Abstract】 In order to understand the mechanismof ef fect of potassium on the photosynthesis andguide to agricultural production, the effect of po-tassium on some photosynthetic characteristics offive rice （Oryza sativa） cultivars at five leaf stageswas studied by water culture. The results show-ed that the net photosynthetic rate of the leaftreated with normal K （40 ppm） was greaterthan that treated with low K （1 ppm）, differencewas statistically significant （P<0.05） in threecultivars. The K content and stomatal conduc-tance of all cultivars depressed significantlyunder low K condition, and the latter was posi-tively linearly correlated with the net photosyn-thetic rate （Y=3.170+0.0503X, r=0.6638）.The chlorophyll content was not decreased bylow K treatment. The activities of photopho-sphorylation and electron transport in isolatedchloroplasts were lower under low K treatment.The activity of photophosphorylation per unitleaf area directly varied as net photosyntheticrate in two K treatments (Y_K1=73+0.1879X,r=0.8078; Y_K40=126+0.1114X, r=0.6688), and a common linear regressionequation （Y=111+0.1299X, r=0.7200）can be used. There was a positive linear cor-relation between the electron transport activityper unit leaf area and net photosynthetic ratein two treatments (Y_K1=115+0.3038X,r=0.9156; Y_K40=152.4+0.1798X, r=0.9182; Fig. 3). The electron transportof chloroplasts from rice leaf at both K levelswas. promoted by exogenous K in the range of1～100 mmol/L. Water photolysis was noteffected but the electron transport activity ofPS II, PS I or their oxidative and reductive sideswas reduced by low treatment: the electrontransport activity from BD-VitC to MV,from H₂O to DCIP and H₂O to MV under lowK condition was 90% of the activity under nor-mal K treatment, and that from DCIP-VitCto MV and from TMPD-VitC to MV about80%.更多还原