不同叶型维西堇菜叶片结构及光合特征比较

Comparison of leaf structure and photosynthetic characteristics between two leaf types of Viola monbeigii

为探讨叶片斑纹的光合适应意义,该文选择有斑和无斑两种叶型的维西堇菜(Viola monbeigii)作为研究材料,采用石蜡切片制片和显微镜观察叶片结构及GFS 3000便携式光合测量仪测量光合参数并进行比较。结果表明:(1)两种叶型维西堇菜气孔均为不等型气孔,有斑叶片上、下表皮气孔密度、栅栏组织(PT)厚度、栅栏组织与海绵组织的比值(PT/ST)均显著低于无斑叶片;而上表皮气孔较大,表现出更适应弱光环境的结构特征。(2)两种叶型维西堇菜暗呼吸速率(R_(d))、初始荧光(F_(o))、最大荧光产量(F_(m))、光化学猝灭系数(q_(P))、非光化学猝灭系数(q_(N))、PSⅡ最大光化学量子产量(F_(v)/F_(m))、实际光化学反应量子效率(Yield)均无显著差异,有斑植株叶片叶绿素含量、最大净光合速率(Pmax)显著低于无斑植株;有斑叶片表观光合电子传递速率(ETR)在光合有效辐射(PAR)处于400~2000μmol·m^(-2)·s^(-1)之间时显著低于无斑叶片,无斑植株的光饱和点(LSP)高于有斑植株,而补偿点(LCP)较低。综上认为,无斑植株PAR利用范围较宽,光合适应能力更强,有利于维西堇菜充分利用环境中有限的资源,保障物种生存;有斑植株具有较适应弱光胁迫的特征,表明叶片斑纹的出现可能是维西堇菜适应林缘弱光环境的一种策略。

In order to explore the photosynthetic adaptation significance of variegated leaves,variegated and non-variegated leaves of Viola monbeigii were selected as materials.The leaf structure was observed by paraffin section and microtechniques,and the photosynthetic parameters were measured by GFS 3000 portable photosynthesis measuring instrument.The results were as follows:(1)The stomata of variegated and non-variegated leaves were all unequal types.However,the stomatal density of the upper and lower epidermis,the thickness of palisade tissue(PT)and the ratio of palisade tissue to sponge tissue(PT/ST)of the variegated leaves were significantly lower than those of the non-variegated leaves;while the stomata of the upper epidermis of variegated leaves were larger than non-variegated leaves,showing more structural characteristics to adapt to the weak light intensity environment.(2)Both leaf types had no significant differences in dark respiration rate(R_(d)),initial fluorescence(F_(o)),maximum fluorescence yield(F_(m)),photochemical quenching coefficient(q_(P)),non-photochemical quenching coefficent(q_(N)),maximal quantum yield of PSⅡ(F_(v)/F_(m))and practical photochemical reaction quantum efficiency(Yield),but the maximum net photosynthetic rate(Pmax)and chlorophyll content in variegated leaves were significantly lower than non-variegated leaves;the apparent photosynthetic electron transfer rate(ETR)of variegated leaves was significantly lower than that of non-variegated leaves when the PAR was between 400-2000μmol·m^(-2)·s^(-1),while the light saturation point(LSP)of non-variegated leaves leaves was higher than that of variegated leaves and the light compensation point(LCP)was lower.In summary,non-variegated plants have a wider PAR utilization range and stronger photosynthetic adaptability,which is conducive to the use of limited resources in the environment and ensures the survival of species.Variegated plants have the characteristics of adapting to weak light stress,indicating that the appearance of variegated leaves may be a strategy for V.monbeigii to adapt to weak light environment at forest edge.