Light gradients and the transverse distribution of chlorophyll fluorescence in mangrove and Camellia leaves

Abstract

The light gradient and transverse distribution of chlorophyll fluorescence in mangrove and Camellia leaves, which have different morphological characteristics, were examined using a micro-fluorescence imaging system reported previously (Takahashi et al., Plant, Cell and Environment 17:105-110, 1994). Epidermal cells scattered light strongly, resulting in an increase in the fluence rate in epidermal cells. For the Camellia leaf, a light gradient was formed by absorption of light by photosynthetic pigments associated with the induction of chlorophyll fluorescence. For the mangrove leaf, a light gradient was formed by backward scattered light within a thick layer of non-assimilatory cells. Light with a low absorption coefficient (515 nm) penetrated deeper than that with a higher absorption coefficient (477 nm and 488 nm) in the Camellia leaf, while light of both wavelengths showed similar profiles in the mangrove leaf. In the mangrove leaves, scattered light declined significantly in the non-assimilatory cell 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 chlorophyll fluorescence in the assimilatory cells, which appear to be well organized to capture weak light.