Control of Flower Formation and Fruit Size in the Pineapple

In the Cabezona variety of pineapple naphthaleneacetic acid (NA) can induce flowers in every month of the year (fig. 1). 2. Amounts of NA as small as 0.05 mg. per plant are capable of inducing flowers in a limited number of plants (1 p.p.m. curve of fig. 1), while 0.25 and 0.5 mg. per plant cause practically 100% flowering. 3. Fruit weight depends upon the size of the plant. The correlation between the number of leaves of a plant and the weight of the fruit it produces was determined (figs. 6-8). 4. Although 2,4-dichlorophenoxyacetic acid (2,4-D) has flower-inducing powers equal to NA (fig. 5), fruit induced by 2,4-D shows a lower average fruit weight as compared with fruit induced by NA (fig. 8 and table 2). This may be due to the adverse effect of 2,4-D on the development of young leaves. 5. Preliminary data indicate that the pineapple may be a short-day plant and that long-day conditions prevent natural flowering but not flowering induced by NA. 6. A method is outlined which makes fruit production in pineapples possible throughout the year without the loss of fruit weight now experienced by commercial growers when they force plants into flower out of season.