Experiments with pairs of strawberry runner plants joined by the stolon and acting as donor/receptor units are reported. Long photoperiods or a light-break treatment on donor plants brought about increased petiole length, increased leaf size, and delayed flower initiation in receptor plants themselves in short photoperiods. The response of receptor plants was increased by exposing donor plants to illumination by full daylight 3 hours earlier each morning than receptor plants. It is thought that this earlier illumination increased translocation from the earlier to the later illuminated plants. In translocation experiments, radioactive P32 moved more freely from the older to the younger plant of each pair, except when the older plants were partially defoliated or when the younger plants were exposed to full light for a longer period of time each day than the older attached plants.
The results are discussed and it is concluded that they are good evidence for the existence of a growth-regulating substance(s) which promotes vegetative growth and inhibits flower initiation. It seems possible that the regulation of vegetative growth and the control of flower induction is principally achieved in the strawberry by a flower inhibiting, vegetative growth-promoting system.