Absorption from culture solution of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and 3-(p-chlorophenyl)-1, 1-dimethylurea (Monuron) by excised barley (Hordeum vulgare L.) roots was studied to determine whether absorption was due to an active or a passive mechanism. Herbicide absorption was followed at low temperature, under anaerobic conditions, and in the presence of metabolic inhibitors and compounds of structure similar to that of the herbicide. Total absorption was divided into two phases, exchangeable and nonexchangeable herbicide, by washing the roots for 1 hour following absorption. Absorption of both exchangeable and nonexchangeable 2,4-D appeared to depend on a supply of metabolic energy which suggests that an active mechanism may be involved. A possible conclusion is that 2,4-D is absorbed by roots by an adsorption mechanism and that energy is required to maintain the integrity of the absorbing surfaces of the cell. In contrast, absorption of Monuron was independent of an energy supply. It is concluded that the bulk of the Monuron absorbed was taken up passively by diffusion.Absorption of mineral salts by plants has been extensively studied and much information on this subject now exists. Although many organic compounds, such as insecticides, fungicides, and herbicides, are applied either directly to plants, or to the soil from where they are taken up by the roots, less information is available on the absorption of organic substances.Both physical and metabolically controlled processes have been shown to control the absorption of indoleacetic acid by pea epicotyl segments and carrot disks (20), and Avena coleoptile sections (17). With Lemna minor the initial uptake of 2,2-dichloropropionic acid (Dalapon) was concluded to be largely under the control of physical factors, whereas the subsequent accumulation was metabolically controlled (18). Absorption of mercuric acetate and phenylmercuric acetate by excised and intact pea roots shows both a passive and an active phase of uptake (19). Hancock (10), using diseased and healthy squash hypocotyls, found that 3-o-methylglucose is taken up in

The AHS neonatal multi-trace element formulation seem to be physio-chemically stable up to 7 days in all three storage conditions when kept in vials.  A decline in iodine concentration is seen after 7 days irrespective of storage conditions. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.