Identity of the Photoreceptors for the Perception of Irradiance in Photosynthetic Light Acclimation in Tomato*

Abstract

The photoreceptors involved in the photosynthetic acclimation of tomato (Lycopersicon esculentum Mill.) to increased irradiance were investigated. Plants were transferred from 100 pmol r r Z s-' cool white fluorescent light to higher irradiances of white light or white light supplemented with blue, red, green or yellow light. In these experiements light of all wavelengths tested was capable of causing acclimation as measured by the rate of light-saturated photosynthesis. It was concluded that the photosynthetic system rather than the blue-absorbing photoreceptor or phytochrome system acts as the photoreceptor for increased irradiance. No acclimation was observed in response to increased CO, levels, but increasing light integral at a constant irradiance was effective in bringing about acclimation. We conclude that acclimation is a response to increased photosynthetic light capture rather than increased photosynthetic carbon fixation, and involves a photon counting mechanism

A blue-light photoreceptor mediates the fluence-rate-dependent expression of genes encoding the small subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase in light-grown Phaseolus vulgaris primary leaves

“…In particular, the cucumber Ih mutant, which behaves as a wild type growing under extremely low red : far-red light ratio (extreme vegetational shade) due to lack of a light-stable phytochrome (L6pez-Juez et al 1992), shows little difference in the chlorophyll a/b ratio compared to the wild type (L6pez-Juez et al 1990a). Alternatively, the pigments associated with the photosynthetic machinery could be involved (Leong and Anderson 1986;Chow et al 1990;Withers et al 1991). Alternatively, the pigments associated with the photosynthetic machinery could be involved (Leong and Anderson 1986;Chow et al 1990;Withers et al 1991).…”