Water extrustion in the trap bladders ofUtricularia vulgaris
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In the trap bladder ofUtricularia vulgaris, increase in sucrose concentrations in bladder lumen fluid decreased resetting rate. Addition of 350 mM sucrose to lumen fluid stopped the resetting. Therefore, water seems to move down the water potential gradient between the lumen and the arm cells of bifid trichomes, which are the site of inlet in the water pathway. Application of dinitrophenol, sodium azide, KCN, monoiodoacetic acid or pentachlorophenol in lumen fluid much reduced the water outflow. Temperature coefficient of bladder resettings was about 2. No effect of darkness on resetting rate was found. These facts show that the resetting requires energy supplied from respiration and there exists an active ion transport mechanism somewhere in the water pathway. No effect on the resetting was seen upon immersing the bladder in 700 mM surcose solution. In the capital cells of the pavement epithelium in its outer and middle zones, which are the site of outlet in water pathway, membrance potential and resistance were lower than those in other cells. These facts indicate that bulk flow of the cell sap from the capital cells to the outside takes place by intracellular hydrostatic pressure.
Key wordsBulk flow Trap bladder Trap resetting Utricularia vulgaris Water and solute transport
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