Developmental-physiological studies on weeds (III) : Floral stimulus movement in and effects of long days on flowering process of beggar-ticks, Bidens frondosa LINNAEUS

The annual weed, beggar-ticks, is a quantative short-day plant. The flowering process was analyzed by preparation of experimental plants with different leaf or branch systems and by their exposure to short or long days in different patterns. We found that the flowering stimulus, florigen, seems to be produced in the leaves exposed to short days for at least three to four days. The florigen needed to evoke a flower initial in a vegetative bud is produced in sufficient amounts by one short-day leaf. The florigen probably moves from the induced leaf (source) to the receptor bud (sink) after assimilation stream. It seems likely that the inhibition of flowering by long-day treatment is not caused by a specific transmissible inhibitor produced in the long-day leaf. The long-day leaf attached at the upper node or on a branch inhibits flowering of the terminal bud simply as a result of competitive blocking of the assimilation stream from the induced short-day leaf attached at the lower node or on an other branch to the terminal bud