中文摘要：

为了明晰缺钾胁迫下光合速率下降的主导因素及其作用机制,在田间条件下设置正常供钾处理（＋K）和缺钾处理（–K）,采用气体交换和叶绿素荧光联合测定技术以及透射电镜技术,研究缺钾胁迫时越冬期甘蓝型油菜品种浙油601的光合特性及叶绿体超微结构。结果表明,缺钾胁迫时叶片光合速率下降了45.1%。尽管缺钾胁迫下叶片气孔导度（gs）明显降低,但其胞间CO2浓度（Ci）增加了66μmol CO2·mol^-1,气孔限制值（Ls）减小了45.7%,说明气孔因素并非缺钾胁迫下油菜叶片Pn下降的主要原因。进一步的叶绿素荧光参数测定结果表明,缺钾胁迫导致油菜越冬期叶片PSII潜在光化学效率（Fv/Fm）和实际光化学效率（ΦPSII）显著下降,说明光系统II反应中心受损;并且缺钾胁迫下油菜叶片叶绿体的长度降低了15.1%、叶绿体厚度增加了22.7%、叶绿体到细胞壁的距离增加了56.1%。由此可见,缺钾胁迫下越冬期油菜叶绿体结构改变及光系统反应中心受损等非气孔因素导致叶片光合速率下降。

英文摘要：

To understand leaf photosynthesis characteristics and its response to K starvation in oilseed rape,a field experiment was carried out on K- deficient soil with K deficiency（- K） and K supply（ ＋ K） treatments.Gas exchange,chlorophyll fluorescence and chloroplast ultrastructure were studied using winter oilseed rape cultivar Zheyou 601 during over- wintering period. Results showed that leaf net photosynthetic rate（ Pn） decreased by45. 1% under- K condition. Although stomatal conductance（ gs） was lower in- K treatment than in ＋ K treatment,intercellular CO2concentration（ Ci） increased 66μmol CO2·mol^- 1. Limiting value of stomata（ Ls） decreased by 45. 7%. Thus the stomatal factor changes were not the main reason for Pndecrease under – K condition. Further evidences from chlorophyll fluorescence measurement showed that both photosystem II（ PSII） maximum photochemical quantum yield（ Fv/ Fm） and PSII actual photochemical quantum yield（ ΦPSII） were declined under- K treatment,which indicated that PSII reaction center was damaged. In addition,K deficiency affected chloroplast ultrastructure of leaves. In K deficient plants,chloroplast length decreased significantly（ with the average of 15. 6%）. Chloroplast thickness and distance from chloroplast to cell wall increased by 26. 9% and 56. 1%,respectively. In conclusion,the non- stomatal factors,e. g. damaged PSII reaction center and chloroplast ultrastructure alteration inhibited leaf Pn under K deficiency.