Elemental concentration in each tissue of Japanese morning-glory (Pharbitis nil) during the growth was analyzed by INAA. Plants were grown in water culture for 4 days under 12-hour light and 12-hour dark condition. During the growth, 10 plants in the same developmental stage were periodically harvested. Then the plants were separated into 9 tissues to determine elemental concentration and water content. There was an elemental specific profile within the plant tissue, for example, Na and K concentrations were high in root whereas Mg and Ca concentrations were high at the upper part of the plants. Among the elements studied, Ca and Mg showed rhythmical change in concentration, increased during the day and decreased during the night. This tendency was especially noted at shoot apex. However, water content in all of the tissue was increased about 6 hours prior to the light period and showed maximum in the middle of the light period. About 6 hour difference of water content movement to those of Ca and Mg concentration suggested that water movement drives more dynamic change of each elemental concentration within a plant.
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