甘蓝型油菜黄化突变体的光合特性及叶绿素荧光参数分析

调查油菜自发黄化突变体(NY)、野生型(NG)及其正反交后代材料(F₁和rF₁)的光合色素含量、光合特性、叶绿素荧光参数及农艺性状，分析五叶期各参数的变化规律。表明，突变体叶绿素a、叶绿素b、类胡萝卜素和总叶绿素均大幅减少，其中叶绿素b减幅最大；净光合速率显著降低，胞间CO₂浓度升高，但气孔导度与野生型等相当，表明光合速率不受气孔限制；光补偿点和光饱和点升高，暗呼吸速率与野生型等相当，表观量子效率和光补偿点处量子效率显著降低；CO₂补偿点、光呼吸速率和羧化效率均显著降低，CO₂饱和点则显著升高；突变体的荧光参数，包括F_o、F_m、F_v/F_m、F_v'/F_m'、Φ_PSII、q_p、NPQ和ETR均显著降低，说明光合色素含量降低导致PSII反应中心捕光能力弱和光化学转化效率低，使叶片光合速率降低。突变体的黄化持续时间较长，对生长发育产生影响较大，单株籽粒产量只有野生型的57.09%，但与正常材料组配F₁的光合特性和农艺性状均能恢复到正常水平。

Photosynthetic Characteristics and Chlorophyll Fluorescence Kinetic Parameters Analyses of Chlorophyll-Reduced Mutant in Brassica napus L.

We investigatedthe photosynthetic pigment contents, photosynthetic characteristics, chlorophyll fluorescence kinetic parameters and agronomic traits at five-leaf stage of the chlorophyll-reduced mutant (NY), wild-type (NG), F₁ and rF₁ of their combinations (reciprocal cross). The results showed that the chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids in the mutant were significantly reduced compared with there in other materials, expecially for chlorophyll b. The net photosynthetic rate (P_n) of the mutant was significantly lower than that of wild-type and their F₁ and rF₁. Relatively high intercellular CO₂ concentration (C_i) and an equivalent stomatal conductance (G_s) in the mutant indicated that stomatal factor was not the limiting factor of the photosynthetic rate. The mutant had higher light compensation point (LCP) and light saturation point (LSP), and its dark respiration rate (R_d) was equal to that of wild-type, whereas apparent quantum yield (AQY) and quantum yield at light compensation point (φ_c) in the mutant were significantly decresed. The CO₂ compensation point (CCP), rate of photorespiration (R_p) and carboxylation efficiency (CE) of the mutant NY were significantly lower than those of the wild-type NG and their combinations of NY×NG and NG×NY, but the mutant had higher CO₂ saturation point (CSP). The fluorescence parameters in the mutant, including F_o, F_m, F_v/F_m, F_v''/F_m'', Φ_PSII, q_p, NPQ, and ETR were significantly reduced. Lower photosynthetic pigment content may be the main reason for low leaf photosynthetic rate which directly leads to the lower light-harvesting capacity and photochemical conversion efficiencies of the PSII reaction center. Moreover, lasting etiolation of leaves in the mutant had a greater impact on its growth and development, but the photosynthetic characteristics and agronomic traits were restored to normal level in F₁ of the cross between the mutant and the normal parent.