Effects of High Humidity on Translocation of Foliar-Applied Labeled Compounds in Plants Part: I

Abstract

With the aid of a critical method for preparing auto-radiographs, both C14 -labeled 2,4-dichlorophenoxyacetic acid and C14-labeled sucrose (resulting from C14 -urea breakdown in the plant) translocated from the cotyledon to roots and shoots of the cotton plant With high humidity the amount translocated was greatly increased. Steam-ringing of various portions of the stem and petioles proved that high humidity permitted a large xylem movement of both compounds from the treated cotyledons into the stem and up into the mature leaves; this type of movement did not occur at low humidity. The large basipetal movement under high humidity was essentially stopped by steam girdling. The effect of high humidity was largely upon the treated leaf.