[C-14]-ASSIMILATE PARTITIONING IN PHOTOPERIODICALLY INDUCED SEEDLINGS OF PHARBITIS-NIL - THE EFFECT OF BENZYLADENINE

Partitioning of [14C]-labeled assimilates was studied in relation to photoperiodic floral induction and evocation in 1-wk old P. nil. Choisy cv. ''Violet'' seedlings. In plants kept under 16 h photoperiods, one 15 h night induced 100% axillary flowering whereas a 24 h night induced both terminal and axillary flowering. A 15 min night break of red light given 8 h after the beginning of the dark period inhibited flowering. Total [14C]-assimilate distribution among major sinks (plumules + epicotyl and roots + hypocotyl) from a single source cotyledon was unchanged by 1 inductive night; import of [14C]-assimilates into shoot apices was increased in induced plants compared to vegetative controls. This increase was several-fold in plants subjected to a 24 h night. N6-Benzyladenine (BA) application to cotyledons or plumules under non-saturating night lengths increased the number of floral buds per plant without affecting the position of the 1st floral bud (i.e., the speed of induction). The same treatment caused increased label accumulation of induced apices, while it only slightly affected non-induced ones. The mode of action of BA on flowering through growth stimulation and resulting assimilate mobilization is discussed.