Absorption and Translocation of 2,4-Dichlorophenoxyacetic Acid and P³² by Leaves

Abstract

Foliar applications of nutrient minerals and the increasing use of systemic pesticides have served to reemphasize the importance of absorption and translocation in plant physiology. Studies of the movement of these materials have an immediate application value; at the same time they can aid in the solution of basic problems in plant behavior.A number of workers (5,12,14,24,30) have stressed the importance of surfactants in increasing the effects of herbicides applied to leaves. Bryan et al (5) and Hauser (12) showed that the rate of absorption of 2,4-D as well as the total qualtity absorbed was increased by lowering the surface tension of sprays. Some of this effect is due to the better wetting leaves (12,21) (25) showed that p32 could be absorbed through leaf surfaces. The latter workers found, however, that this absorption was reduced by the single surfactant tried in their work.The older work on translocation is reviewed by Curtis (8). Mlore recent work, particularly as it applies to the mass-flow hypothesis, is reviewed by Crafts (6). Translocation of organic molecules, up or down, is normally limited to the phloem, while inorganic substances may move either in the xylem or phloem (17

Effects of High Humidity on Translocation of Foliar-applied Labeled Compounds in Plants. II. Translocation from Starved Leaves

“…Carboxyl-labeled 2,4-D-C14 purchased froml Tracerlab, andl having a specific activity of 6.03 nmc 1 Received Jani. 15 …”

“…It has been established for some time that translocation of growth substances is dependent upon, and coincides with, the transport of assimilates from leaves, and that movement of such substances does not take place from chlorotic leaves (7) or from starved leaves (1,2,10,11,13,15).…”

Solute Distribution in Sugar Beet Leaves in Relation to Phloem Loading and Translocation

“…Numerous workers have postulated that an active process in the minor vein phloem serves to drive mass flow of solutes (1,2,4,5,7,10,14,22,25,26). In support, various investigators have used autoradiography to demonstrate loading of minor vein phloem (9,14,16,17,23).…”

Translocation of Organic Substances in Trees. III. The Removal of Sugars from the Sieve Tubes in the White Ash (Fraxinus Americana L.).

“…We made no attempt to R-_ STACHYOSE check this anatomically. workers (1,2,21), may be regarded as a metabolic "pressure-pump." It raises the turgor within the the point equivalent to the time of defoliation sieve tubes of the leaves.…”

“…In order to explain our previous observations it was proposed that there is an enzymatic removal of D-galactose units which results in a gradual break-down of the higher oligosaccharides, stachvose and raffinose, as they move down the tree (24). In the present investigation three ash trees have been defoliated, thus cutting off the supply of 1 Receivedl December 30, 1957. photosynthates to the phloem, and the changes that took place in the sieve tubes after this treatment have been followed. A similar study has been made of the changes in the phloem during the natural leaffall in autumn.…”