Partitioning of [14C]‐labeled assimilates was studied in relation to photoperiodic floral induction and evocation in one‐week‐old Pharbitis 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 one inductive night; however, import of [14C]‐assimilates into shoot apices was increased in induced plants compared to vegegative 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 first floral bud (i.e. the speed of induction). The same treatment caused increased label accumulation in 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.
Floral induction by night interruption of Fuchsia hybrida cv. Lord Byron, a quantitative long‐day plant with decussate phyllotaxis and an indeterminate flowering habit, altered neither the rate of leaf initiation nor the rate of leaf expansion; nor did flower initiation and development change the vegetative growth of the plants. This was diagnosed using plastochron duration and plastochron ratio measurements before, during, and after a 10‐day induction period. A comparison between indeterminate and determinate flowering is made using these two parameters.
Floral induction by night interruption of Fuchsia hybrida cv. Lord Byron, a quantitative long‐day plant with decussate phyllotaxis and an indeterminate flowering habit, altered neither the rate of leaf initiation nor the rate of leaf expansion; nor did flower initiation and development change the vegetative growth of the plants. This was diagnosed using plastochron duration and plastochron ratio measurements before, during, and after a 10‐day induction period. A comparison between indeterminate and determinate flowering is made using these two parameters.
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