Light Gradients and the Transverse Distribution of Chlorophyll Fluorescence in Mangrove andCamelliaLeaves

The light gradient and transverse distribution of chlorophyllfluorescence in mangrove andCamellialeaves, which have differentmorphological characteristics, were examined using a micro-fluorescenceimaging system reported previously (Takahashiet al., Plant,Cell and Environment17: 105–110, 1994). Epidermal cellsscattered light strongly, resulting in an increase in the fluencerate in epidermal cells. For theCamellialeaf, a light gradientwas formed by absorption of light by photosynthetic pigmentsassociated with the induction of chlorophyll fluorescence. Forthe mangrove leaf, a light gradient was formed by backward scatteredlight within a thick layer of non-assimilatory cells. Lightwith a low absorption coefficient (515 nm) penetrated deeperthan that with a higher absorption coefficient (477 nm and 488nm) in theCamellialeaf, while light of both wavelengths showedsimilar profiles in the mangrove leaf. In the mangrove leaves,scattered light declined significantly in the non-assimilatorycell layer which is in front of the assimilatory cells. Light,the intensity of which was reduced to approx. 10% of the maximum,was well scattered and induced a considerable amount of chlorophyllfluorescence in the assimilatory cells, which appear to be wellorganized to capture weak light.Copyright 1998 Annals of BotanyCompany fluorescence, intact leaf, light gradient, mangrove (Rhizophora mucronataLamk.),Camellia japonicaL.