Changes in the mitotic cycle in lateral root meristems of Vicia faba following kinetin treatment

Functions of Hormones at the Cellular Level of Organization

“…This is consistent with the suggestion that the QC is high in cytokinin since prolonged exposure of root meristems to cytokinin extends G 1 ( VAN'T Hop 1967, MACLEOD 1968. Reduced levels of auxin may also contribute to slow mitotic cycling in the QC.…”

“…Under some conditions a 35% decrease in the duration of S accompanies kinetinenhanced DNA synthesis (MACLEOD 1968). This implies an inverse relationship between the rate of DNA synthesis and the duration of S. Although this is consistent with the observation that mitotic cycle time increases with DNA content in some cases (V AN'T HOF 1965), this has not held in all instances (FRIEDBERG and DAVIDSON 1970).…”

“…Cytokinins are reported to affect both the Gland G 2 phases of the cell cycle of root meristems, causing a reduction in G 1 (MACLEOD 1968) and a lengthening of G 2 (MACLEOD 1968, VAN'T HOF 1968. This indicates that even though cytokinins may act most directly on a particular step of the cell cycle (JOUANNEAU 1971, FOSKET andSHORT 1973), they may have secondary effects on biochemical pathways important to other phases of the cycle (BERGMANN 1965).…”

Some Observations on the Growth of Lateral Roots of Vicia Faba L. And Their Response to Colchicine Treatment

“…Thus, a gradual increase in the level of auxin in the root apical meristem of V. faba during root elongation could account for the decrease in root growth rate, which takes place as these roots lengthen (Hall, Lajtha and Clowes, 1962) and for the decreased rate of cell division found several days after excised roots were grown in culture (Brown, 1972). Such increases in hormone levels would also provide an explanation as to w'hy changes take place m p^ during root development (MacLeod, 1973b; Table i) as treatments with growth factors (MacLeod, 1968(MacLeod, , 1969 are known to change the proportions of cells in root meristems which have a short cycle time. Similarly, since auxins (Davidson, MacLeod and Taylor, 1965;Davidson and MacLeod, 1966;MacLeod and Davidson, 1966) and other growth factors (Nagl, 1972b) modify the effects of colchicine treatment on mitotic index and the relative frequencies of cells in prophase and metaphase, an increase in the level of growth factors in the root apical meristem as the root elongates could account for the change in response of these laterals to colchicine during root development.…”

Direct introduction of DNA into embryonic axes of Glycine max by microprojectile bombardment

“…This would appear to contradict earlier studies using cultured cells (Simard, 1971;Fosket and Short, 1973) that suggested that the effects of cytokinin were not mediated by modifications of DNA synthesis. The effect of cytokinin on DNA synthesis, however, may depend on the state of differentiation of the cells (Evans, 1984;MacLeod, 1968). Van't Hof (1968) Alternatively, BAP is a nucleotide analog that may interfere directly or indirectly (after conversion to other forms) with the enzymes involved in DNA replication.…”