The Control of Flowering in the Strawberry Fragaria ananassa Duch1

Activity of gibberellin-like substances was lacking in leaves of strawberry plants at time of flower initiation, but peduncle elongation was accompanied by significant activity of two substances probably related to GA3 and GA7. Exogenous gibberellin (GAS), applied to strawberry plants at the flower-differentiation stage, strongly promoted peduncle elongation, while similar application of the growth-retardant (2 chloro-ethyl) trimethylammonium chloride (CCC), an inhibitor of gibberellin biosynthesis, inhibited peduncle elongation. These treatments also affected subsequent runnering, GA increasing the number of runners, as well as their mean individual length, while CCC caused the opposite effect. Application of gibberellin immediately after flower-bud initiation, but before peduncle emergence, affected the distribution of fruit yield. GA-treated plants produced more than untreated ones in the first half of the fruiting season, but the situation was reversed in the second half of the season—so that total yields were unaffected. It was suggested that the exogenous gibberellin hastened yield by anticipating the endogenous gibberellin which is normally formed at a somewhat later stage in the plant's development. The parallel responses with regard to elongation of vegetative runners and flower peduncles together with the data of the other experiments seem to indicate that peduncle elongation is a typical vegetative growth response enhanced by gibberellin and checked by substances which inhibit biosynthesis of endogenous gibberellin.