The Diurnal Variation in the Translocation of Minerals across Bean Roots

Abstract

By use of radioisotopes the capacity of bean roots to absorb PO4 and Rb, and to translocate the ions to the shoot was studied at 4 hr. intervals over a 24-hr. day. Max. absorption and translocation occurred about midday, min. about midnight. Low-salt, high-sugar plants were most active in absorption and translocation. The midday max. in translocation was found in plants held in darkness. Light accelerated translocation. No consistent correlation was found between root sugar concn. and root activity. Sugar applied to the roots had little effect. Greater percentages of absorbed Rb than PO4 were translocated, and the daily increase in translocation rate began earlier and continued later.