Phototactic chloroplast displacement in the photosynthetic mutant, Lemna paucicostata strain 1073

The photosynthetic mutant, strain 1073, of Lemna paucicostata Torr. (L. perpusilla Hegelm.) which has a block in the electron transport chain between plastoquinone and cytochrome f is capable of light-induced chloroplast displacement movements. At 8000-14 000 lx, chloroplasts of the mutant move from their position adjacent to the inner periclinal wall of the mesophyll cells to the anticlinal walls, i.e. along those walls parallel to the direction of the light. Light does not appear to enhance respiration of the photosynthetic mutant or of the wild type strain (6746). These and other results support the idea that chloroplast displacement in light is not solely the result of light effects on photosynthesis and respiration.