Abstract
It was found that floral induced stems of flowering tobacco (Nicotiana tabacum cv. Wis. 38) plants contain large amounts of rapidly renaturing DNA, whereas non-induced stems of vegetative plants contain only small amounts. The striking qualitative difference in DNA between stems of flowering and vegetative plants mimics the over-all quantitative difference in DNA content (on a fresh weight basis). Therefore, the extra DNA in stems of flowering plants seems, at least in part, to represent preferential synthesis of rapidly renaturing DNA. Rapidly renatured (flowering plants) was purified (cesium chloride gradients) from heated-cooled DNA solution and under non-inductive conditions was tested for floral activity. When rapidly renatured DNA in buffer solution is supplied to axillary vegetative buds of vegetative plants and then the axillary buds are defoliated every 4th day for 12 days, the treated buds change into flower buds. Control axillary buds supplied buffer solution alone remain vegetative. In stem segments from flowering plants, the concept, discussed in previous reports, that IAA may modify in vitro bud expression by directly affecting DNA synthesis was reviewed. On the basis of this report, the concept is elaborated by proposing that IAA may act partially in bud expression by directly suppressing synthesis of rapidly renaturing DNA.