基于叶绿素荧光成像及荧光参数分布特征的叶片光合异质性定量分析

Quantitative Analysis of Leaf Photosynthetic Heterogeneity Based on Chlorophyll Fluorescence Imaging and Distribution Characteristics of Fluorescence Parameters

植物叶片光合作用具有高度的空间异质性,叶绿素荧光成像技术为叶片光合异质性的研究提供了便利,但叶片光合异质性的定量分析并没有得到广泛应用。本文利用ImagingPAM叶绿素荧光成像系统,获得中亚热带地区越冬期小叶榕(Ficus microcarpa)阳生叶和阴生叶的叶绿素荧光参数图像,并利用仪器的分析软件对其进行分析,定量比较了阳生叶和阴生叶的光合异质性特征。研究发现:越冬期小叶榕阳生叶的光合异质性和光抑制程度明显高于阴生叶,变异系数可作为光合异质性的定量指标。低温强光导致阳生叶坏死率(P_(LN))达4.30%,并有53.30%的区域处于严重光抑制(0<F_(v)/F_(m)<0.627),但仍有42.27%的区域仅为轻度光抑制(0.627≤F_(v)/F_(m)<0.800)。而低温弱光并未造成阴生叶坏死和严重光抑制。通过对光系统Ⅱ(PSⅡ)的实际光合效率(Y(Ⅱ))、调节性能量耗散的量子产额(Y(NPQ))和非调节性能量耗散的量子产额(Y(NO))荧光参数异质性的定量分析表明,阳生叶具有相对较高的光化学能力,阴生叶则具有相对较高的热耗散能力;冬季强光虽然会导致小叶榕阳生叶PSⅡ严重激发压积累,存在严重光抑制的潜在风险,但其致死面积并不大,叶片中仍存在一定面积低激发压的低风险区,而低温弱光下的阴生叶则主要以低风险区域为主。

Leaf photosynthesis has high spatial heterogeneity,and chlorophyll fluorescence imaging technology provides convenience for the study of leaf photosynthetic heterogeneity,however,the analytical method for quantifying photosynthetic heterogeneity has not been widely used yet.In this study,the chlorophyll fluorescence images for the sunny and shady leaves of Ficus microcarpa in the mid subtropical region during overwintering period were obtained by using the PAM chlorophyll fluorescence imaging system(Walz,Germany),and the photosynthetic heterogeneity characteristics of sunny and shady leaves were quantitatively analyzed respectively.The results showed that the degree of photosynthetic heterogeneity and photoinhibition of sunny leaves were significantly higher than those of shady leaves for F.microcarpa during overwintering,and the coefficient of variation(C_(V))could be used as a quantitative index of photosynthetic heterogeneity.For sunny leaves 4.30%necrotic areas,53.30%severe photoinhibition areas(0<F_(v)/F_(m)<0.627)and 42.27%mild photoinhibition leaf areas(0.627≤F_(v)/F_(m)<0.800)were observed under low temperature but high light condition,respectively.On the other hand,for shady leaves lesser photoinhibition and leaf necrosis were observed under low temperature and low light condition.Furthermore,the quantitative analysis of other fluorescence parameters,such as effective quantum yield of photosynthetic systemⅡ(PSⅡ)photochemistry(Y(Ⅱ)),quantum yield of regulated energy dissipation(Y(NPQ))and quantum yield of non-regulated energy dissipation(Y(NO)),showed that the sunny leaves possessed relatively higher photochemical ability,while the shady leaves had relatively higher heat dissipation capacity.In addition,although in winter the high light would lead to the serious accumulation of excitation pressure of the PSⅡin sunny leaves,which indicated potential risk of serious photoinhibition stress,the necrotic areas were not large,and there were still some low-risk areas with low excitation pressure in sunny leaves.However,the shady leaves under low temperature and low light were mainly low-risk areas with low excitation pressure.