Prevention by 2,4-Dichlorophenoxyacetic Acid of an Increase in the Rate of Phosphate Utilization, caused by the Prolonged Treatment of Segments of Pea Stems in Maleate Buffer

Abstract

WHILE examining the influence of 2,4-dichlorophenoxyacetic acid (2,4-D) on the absorption of ions by epicotyl segments of etiolated peas, it was established that if freshly cut segments are first placed in aerated, distilled water or 0.01 M maleate buffer (pH 5.2) for 12 h, their ability to absorb and esterify inorganic phosphate in a given time (1 h) is increased 12-fold. This marked increase in the rate of phosphate absorption necessitated further study before the effects of 2,4-D on the uptake of ions could be further elucidated. On the basis of this work, which has been reported elsewhere¹, it is concluded that one of the basic changes occurring in the segments during the period in buffer or water is an increase in the rate of synthesis of protein, which in turn results in an increased rate of absorption of phosphate. An increased turnover of protein when pea segments were placed in water for 24 h was reported by Christiansen and Thimann² in 1950. Recently, Click and Hackett³ have suggested that the increased respiratory rate and other metabolic changes occurring when potato slices are similarly treated depend on the synthesis of new RNA and protein.