MITOTIC AND STRUCTURAL EFFECTS OF NITRALIN AND BUTRALIN ON RYEGRASS (LOLIUM-PERENNE L) ROOT-MERISTEMS

Saturated solutions of nitralin or butralin were used to treat the germinating florets of Lolium perenne L. var. Manhattan in a growth chamber to evaluate the induced mitotic and structural effects. Examination of structural changes showed suppressed root elongation and increased radial root enlargement. The response to nitralin was observed at 1 h, whereas a weaker response was first observed with butralin at 12 h. Cortical and epidermal cells close to the apex, treated with either herbicide, were enlarged and more vacuolate. Normal mitotic figures were reduced by 76% and 36% after 1 h following treatment with nitralin and butralin, respectively. Division figures differed markedly between the two herbicides. Nitralin-treated cells formed polymorphic nuclei with an enlargement of nuclear volume and an increase in ploidy level. Butralin decreased the number of prophase division figures, but increased the number of nuclei per cell, yielding a multi-nucleate cell. Nitralin effects on cell divisions resemble those caused by the other dinitroaniline herbicides trifluralin, oryzalin and pendimethalin. Butralin effects on cell division more closely resemble those reported from the carbamates, propham and chlorpropham.