Summary
The deviation from first order commonly observed in phototransformation kinetics of phytochrome in vivo is due to a light-intensity gradient within the sample. This gradient was measured and was found to approach that predicted by the Kubelka-Munk theory of light scatter in turbid materials. The influence of this gradient is eliminated and first-order phototransformation kinetics are obtained, when either (i) thin samples of translucent (low optical density) material of high phytochrome content are measured directly; or (ii) thin samples of opaque (high optical density) or translucent material are sandwiched between two layers of light-scattering material. This result is consistent with the existence of only one population of photoreversible phytochrome molecules in vivo.
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Schmidt, W., Marmé, D., Quail, P. et al. Phytochrome: First-order phototransformation kinetics in vivo . Planta 111, 329–336 (1973). https://doi.org/10.1007/BF00385552
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DOI: https://doi.org/10.1007/BF00385552