Flowering 257 



mg./l. naphthaleneacetic acid are commonly used. The concentration 

 of the auxin sohite does not have a large effect on the results ob- 

 tained, but the governing factor is rather the actual amount of auxin 

 which reaches the plant. Van Overbeek (1946) has shown that several 

 different concentrations of auxin would be effective, provided only 

 that approximately 0.25 mg. of actual auxin was applied to each plant. 



Factors in Success 



As in all of the other uses of auxins in agriculture, the condition 

 of the plant plays a very important role in the success of flower forc- 

 ing. Pineapple plants high in carbohydrate are the most imiform in 

 their response to auxins. The time of day at which the auxin is 

 ajjplied has a strong influence upon its effectiveness (Nightingale, 

 unpublished). 



It was seen in chapter VI that light and temperature have a pro- 

 found effect on the absorption and translocation of growth regulators, 

 and these two factors likewise strongly modify the spray's effectiveness. 

 Of the two, light may be the most crucial, for unpublished experi- 

 ments by Nightingale have revealed that on cloudy days the effective- 

 ness of the auxin spray in Hawaii may be reduced 50 per cent. 



Several side effects have been observed following the use of auxin 

 sprays. The first of these is the abnormal elongation of the peduncle. 

 This tall, thin structure is often unable to sustain the pineapple fruit 

 following auxin forcing, and consequently excessive bending or even 

 breaking of the peduncle under the ripening fruit frequently occurs. 

 Another auxin spray developed to strengthen the peduncle is de- 

 scribed in chapter XVII. 



A second side effect is that of reducing the slip production. Be- 

 cause pineapple plants are propagated by the lateral peduncle buds, 

 or slips, such a reduction can have important implications for pine- 

 apple plantation operations. 



A third side effect is the reduction in size and quality of the fruit 

 due to the forcing procedure. Pineapple fruit size and quality are 

 intimately related to the size of the plant and its stage of development 

 (van Overbeek, 1946). It is not surprising then to find that when 

 all plants are forced to flower regardless of whether or not they are 

 large enough to flower naturally, the average fruit size and quality are 

 reduced. 



A fourth and extremely important side effect of forcing flowering 

 is the production of fruits ready for harvest almost simultaneously 

 over the entire field. 



