Shoot Zone Uptake of Soil‐applied Herbicides*

Abstract

Summary. Studies were conducted to determine the effects of herbicide placement at different zones of maize (Zea mays L.) and pea (Pisum sativwm L.) shoots below the soil surface after emergence. Soil was removed from around the shoots and replaced with herbicide‐treated soil. A wax barrier ensured separate exposure of the zones to treated soil. EPTC, chlorpropham, propham and sulfallate did not affect pea shoot growth, but in maize the shoot zone adjacent to the crown root node was extremely sensitive. Treatment in this area markedly reduced growth and severely inhibited the crown roots. The difference in susceptibility between these species may he due to the location of the growing point relative to the treated soil. Shoots of maize and pea were sensitive to diuron. In maize the shoot adjacent to the crown root node and the tissue of the first internode were the most susceptible. In pea the‐ uppermost shoot (beneath the soil surface) was the most sensitive. Trifluralin did not affect growth of maize and pea when placed in the shoot zone after emergence, although the crown roots of maize were severely inhibited. Naptalam, dalapon and 2,4‐D did not affect growth of maize under similar conditions, and of these only 2,4‐D reduced growth of pea. Zone d'abiorption des tiges pour les herbicides appliqués sur h sol

SHOOT ZONE UPTAKE OF SOIL‐APPLIED HERBICIDES IN PISUM SATIVUM L.

“…the base of the coleoptile was the most sensitive zone to di-allate. Prendeville (1968) showed that the lower shoot, including the coleoptilar internode in wheat, oats and barley was the most sensitive region to 5-ethyl-jVl/Vdipropylthiolcarbamate (EPTC) while in sorghum, no such differential sensitivity existed. In maize the shoot region around the growing point and crown root node was the most sensitive region to isopropyl JV-phenylcarbamate (propham), isopropyl jV-(3-chlorophenyl)carbamate (chlorpropham) and EPTC (Prendeville, 1968).…”

“…Prendeville (1968) showed that the lower shoot, including the coleoptilar internode in wheat, oats and barley was the most sensitive region to 5-ethyl-jVl/Vdipropylthiolcarbamate (EPTC) while in sorghum, no such differential sensitivity existed. In maize the shoot region around the growing point and crown root node was the most sensitive region to isopropyl JV-phenylcarbamate (propham), isopropyl jV-(3-chlorophenyl)carbamate (chlorpropham) and EPTC (Prendeville, 1968). The presence of adventitious roots on the shoots of maize and sorghum was shown to be significant in herbicide uptake and foliage injury with jV'-(3,4-dichlorophenyl) jVjV-dimethylurea (diuron), 4-ethylamino-6-isopropylamino-2-methylthio-l,3,5-triazine (ametryne) and 5-chloro-6-methyl-3-<-butyluracil (terbacil).…”

“…JVjV-dimethyl-aa-diphenylacetamide (diphenamid) on the other hand, while severely inhibiting these roots, did not cause foliage injury (Nishimoto & Warren, 1971). Prendeville (1968) showed in pea, in contrast to maize, that the shoot below the soil surface after plant emergence was insensitive to propham, chlorpropham and EPTC. This was attributed to the different location of the growing point in the two species at time of treatment.…”

“…This was attributed to the different location of the growing point in the two species at time of treatment. Further studies (Prendeville, 1968) indicated that the lower 2*5 cm of pea shoot was insensitive to diuron and 2-chloro-4,6-bisethylamino-l,3,5-triazine (simazine), while treatment of the upper shoot did affect plant growth.…”

Site of Uptake and Action of Thiocarbamate Herbicides and Herbicide Antidotes in Corn Seedlings

“…A number of reports (1)(2)(3)(4)(5)(6)(7) have been concerned with the site of uptake of EPTC in various plant species. In some species root exposure to the treated soil gave more injury than shoot exposure and in other species shoot exposure gave more injury (1,5).…”