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ORIENTATION MOVEMENTS OF CHLOROPLASTS IN Vallisneria EPIDERMAL CELLS: DIFFERENT EFFECTS OF LIGHT AT LOW‐ and HIGH‐FLUENCE RATE *
Author(s) -
Izutani Yasuhiko,
Takagi Shingo,
Nagai Reiko
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb01690.x
Subject(s) - chloroplast , biophysics , irradiation , blue light , botany , red light , light intensity , biology , chemistry , optics , biochemistry , physics , gene , nuclear physics
— Epidermal cells of Vallisneria gigantea have a large central vacuole which is surrounded by a thin layer of cytoplasm. The chloroplasts are distributed over all six cytoplasmic layers of an approximate cuboid. In low‐intensity light, the accumulation of chloroplasts in the side facing the outer periclinal wall (the P side) continues for several hours. Red light (650 nm) shows the highest effect and induces such an accumulation even at a fluence rate of only 0.02 W/m 2 . In response to high‐intensity light, the chloroplasts move to the sides that face the anticlinal walls (the A sides) within a few tens of minutes. Blue light (450 nm) is most effective in inducing this movement. At a fluence rate of 1.51 W/m 2 , the reaction is induced in only half of the specimens. Neither red nor blue light can induce any orientation movement in the presence of 100 μg/ml of cytochalasin B. The chloroplast movements in the P side have been examined with a time‐lapse video system. When cells, in which the chloroplast accumulation has been completed after red‐light irradiation, are subsequently irradiated with blue light, the rapid movement of chloroplasts to A sides is induced. However, a considerable number of chloroplasts remains in the center of the P side. The same is true of cells in which the chloroplasts have not accumulated in the P side because of cytochalasin B treatment during red‐light irradiation, when such cells are irradiated with blue light after removal of the drug. Some anchoring mechanism seems to work in low‐intensity light to render the chloroplasts immobile in the P side.