The movement of 2,4-dichlorophenoxy acetic acid in root segments of Pisum sativum L

Abstract

The movement of 2,4-Dichlorophenoxy acetic acid (2,4-D) through subapical segments of the primary roots of Pisum seedlings has been investigated using [1-(14)C]2,4-D.Donation of [1-(14)C]2,4-D to the apical or basal ends of Pisum root segments at 25°C in darkness revealed a preferential movement of the compound towards the root apex i.e. an acropetal polarisation. Thus the movement of [1-(14)C]2,4-D into receiver blocks applied to the apical ends of the segments is greater than that into receiver blocks applied to the basal ends of the segments The low level of basipetal transport appears to be associated with a restriction of the movement of [1-(14)C]2,4-D to the half of the segment nearest the donor block.Acropetal transport of 2,4-D is faster than basipetal transport in root segments maintained at 15° and 35° C but is slower than basipetal transport if the segments are maintained at 25°C. Maximum velocitees are 0.71 and 0.83 mm h(-1) for acropetal and basipetal transport respectively.Evidence from experiments carried out (a) in an anaerobic environment in the presence or absence of sodium fluoride and (b) over a range of temperatures from 1-35°C, indicates that the movement of [1-(14)C]2,4-D is dependent on the metabolic activity of the Pisum root segments.Release of (14)CO2 during transport of [1-(14)C]2,4-D is small and supports chromatographic evidence that negligible degradation of the 2,4-D molecules takes place during transport through the root segments.