Groioth Regulators in Agriculture 807 



pineapple plantations is not yet on a commercial scale. A moment's 

 digression to Figure 2 will illustrate the problem. Although the crop 

 from slips planted in the fall initiates inflorescences quite uniformly 

 in December of the succeeding year and is harvested as a unit the 

 following summer, to handle all the crop in this way would exceed 

 the fruit-packing capacity of the canneries. Consequently, plantations 

 are compelled to harvest the year around, and it is in trying to make 

 the population in a field of fall-planted suckers, or in a field planted 

 in an oif-season, behave as a unit that the problem arises. Commonly, 

 in such fields, a percentage of the plants will differentiate in one 

 month, more in another couple of months, and so forth as shown in 

 Figure 2. Fruits and plants of different physiological ages in the same 

 field increase costs by increasing the number of harvest periods and 

 of harvest rounds within these periods, and they make maintenance 

 of optimum fertilization and insecticide schedules quite impossible. 

 Moreover, precocious fruits from small plants are often small. The 

 development of an acceptable inhibitor of precocious flowering is 

 therefore quite important. 



Figures 3 and 4 will show why the use of NAA at 1,000 p.p.m. to 

 inhibit flowering has not become a general practice, despite the seri- 

 ousness of the problem. Figure 3 represents an untreated 15-month- 

 old nonfruiting pineapple plant stripped down and the leaves ar- 

 ranged from left to right according to their position on the stem (oldest 

 leaves at the bottom). It will be seen that as the pineapple plant grows 

 the length of the longest leaf produced increases with age of the plants 

 to a maximum. It will continue to hold this maximum until flowering 



1201" ,i<''," 



100 

 S 80 



- 60 



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40 

 20 



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Leaves -2_s^,(u,'' ,«' 



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 1 



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- About 25 leaves Stem - 



from original ^ , 



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Increasing age of plant—*- 



Fig. 3. Lengths of leaves of nonfruiting pineapple plant 15 months after plantnig. 

 Oldest leaves at left; each mark one leaf tip. (Leaves with broken tips omitted.) 



