遮阴对丰香草莓光合作用及叶绿素荧光特性的影响

以盆栽丰香草莓为材料,研究了遮阴处理对草莓光合作用及叶绿素荧光特性的影响。结果表明,遮阴处理增加草莓叶柄长度、叶面积以及光合色素含量,但降低了比叶重;遮阴处理显著降低草莓叶片的羧化效率(CE)、暗呼吸(Rd)、光补偿点(LCP)和光饱和点(LSP),提高了其表观量子效率(AQY)和CO2补偿点(CCP)。遮阴后草莓Pn日变化由“双峰”型变为“单峰”型,日光合总量显著低于对照,早晚时分水分利用率(WUE)有所下降。遮阴后,叶片气孔导度(Gs)提高,蒸腾速率(Tr)下降,可能与叶面温度下降有关。叶绿素荧光动力学测定显示,遮阴处理草莓叶片的初始荧光(Fo)和PSⅡ最大光化学效率(Fv/Fm)日变化曲线与对照相似,但Fo值始终低于对照,Fv/Fm值显著高于对照。以上参数表明丰香草莓对弱光环境有一定的适应能力,遮阴处理可以减轻强光下的草莓叶片光抑制程度,提高植株对光能的利用能力,但同时也需要注意提高环境中CO2浓度。

Effects of shading on photosynthesis and chlorophyll fluorescence characteristics of Toyonoka strawberry cultivar

Experiment was conducted with potted strawberry cultivar Toyonoka for studying effects of shading on its photosynthesis and chlorophyll fluorescence characteristics. The results showed that the petiole length, leaf area and the content of chlorophyll and carotenoid under shading condition were higher than those of control, but the specific leaf weight (SLW), carboxylation efficiency (CE), dark respiration (Rd), light saturation point (LSP) and light compensation point (LCP) became lower. Furthermore, shading increased the apparent quantum yield (AQY) and the CO2 compensation point (CCP), which represented that the plants would be more efficient to transfer light quantum into chemical energy under low light stress, but the affinity to CO2 was decreased. Because of shading, the highest sunlight intensity at noon, about 2000 μmol/m2·s, declined to 600 μmol/m2·s, and the diurnal variation, a double-peak curve, of net photosynthetic rate (Pn) of strawberry under nature environment became a single-peak, and the daily accumulation of photosynthate decreased about 38%. Shading increased the leaf stomatal conductance (Gs) but the transpiration rate was lower than that of control, which was the result of lower temperature under shading. Shading also decreased the minimal fluorescence (Fo) but promoted the PSⅡmaximal photochemical efficiency (Fv/Fm), implying that shading might protect integration of the photosynthetic membrane systems and photochemical efficiency against the strong light stress. The results above indicated that shading was indeed beneficial for strawberry growth and alleviated photosynthetic photoinhibition, but it should be noted to increase CO2 concentration for strawberry under low light environment.