Translocation of the Reproductive Stimulus in Sugar Beets

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Abstract
Shoots of annual beets exposed to long days developed seedstalks. Shoots exposed to short days, even though connected to shoots exposed to long days, remained vegetative. Shoots kept in darkness that were also connected to shoots exposed to long days developed seed-stalks, even though also connected to short-day exposed shoots that remained vegetative. These results indicate that substances conducive to reproductive development may be translocated with the carbohydrates. Annual-biennial grafted beets, subjected to differential photoperiods, developed as follows: 1) Long-day-exposed biennial snoots failed to develop seedstalks when they were not also subjected to cool temps.; 2) darkened annual shoots of the same grafted beets did not develop seedstalks; 3) about one month was required to initiate seedstalks in long-day-exposed annual shoots; and 4) darkened biennial shoots of the same beets also developed seedstalks during the following month. These results indicate that biennials are not able to synthesize sufficient reproductive-inducing substances as a result of photoperiod alone, as annuals do, but also require cool-temp. exposure. Reproductive-inducing substances produced by biennials as a result of thermal and photoperiodic induction and those produced in annuals as a result of photoperiodic induction alone appear to be in effect similar. A simple and effective method of grafting such material is described.

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