Responses of Crop Plants to O-Isopropyl N-Phenyl Carbamate

Abstract

The external responses of over 50 spp. to soil applications of the carbamate at planting time were detd.; detailed histo-cytological observations of oat and barley plants treated with the carbamate are recorded. Some treatments involved applications of the substance to soil, nutrient-solution, and irrigation-water cultures and also to the tops of established plants. 13 monocot spp. treated at the germination stage showed similar gross responses were characterized by lack of root and shoot elongation, with concurrent swelling of these parts. Roots were stubby and bulbous; the coleoptilar region was markedly swollen. Young established cereals, treated by soil application of the carbamate, ceased to grow acropetally; the leaves became dark green. Of 39 dicot spp. exposed to the compound at the germination stage, 15 showed some responses. Plants of 6 of these spp. largely recovered from the treatment; in 9 they were permanently inhibited. In all the latter 9 spp. the hypocotyl failed to elongate normally and became enlarged; the root system was much stunted. Most of the dicot spp. responding to the carbamate developed only to the 2-leaf stage. Applications of the carbamate to tops of oat plants in the boot stage of development resulted in cessation of panicle growth; similar applications at the seedling stage induced no responses. These differential responses are related to stage of development. Marked abnormal cytological behavior occurred in the roots and shoots of oat and barley plants treated with the substance; this was characterized by an interrupted mitotic cycle, blocked metaphases, multinucleate cells, occurrence of giant nuclei, and a highly increased chromosome no. in certain cells of both root and shoot. Cell division ceased in the apical meristems of both root and shoot; great cell enlargement and maturation occurred in these cells and in those in the process of expansion. The abnormal cytological behavior occurring in the root and shoot of oat and barley plants treated with the substance can be correlated with subsequent survival of the plants or with abnormal development. Possible agronomic applications of these results in vegetational control and the probable usefulness of this carbamate in genetic and cytological studies are suggested.