808 D. P. Gowing 



100 



-^80 

 o 



£60 



c 



Leaves -> i» " i''» 



« , A 'ill 



,' Area of n \ 



ii disorganized a 



- 40- ,•' leaf tissue 



o 

 -J 20 



About 22 leaves ^^ Constricted 



from original .^ stem and 



slip NAA R j^ adventitious^ 



oool'nl N.AA/V^ 



appl'n^ XAA/v*^ roots """^ "^Q | 



yy — - 



Increasing age of plant -^ 



Fig. 4. Representation of 15-month-old pineapple plant 5 months after treatment 

 with NAA at 1,000 p.p.m. Some rotting of leaf bases and proliferation of adven- 

 titious roots on basal leaf tissue at R. 



is induced either naturally or artificially. (The shorter leaves on the 

 right are the immature leaves of the growing point at the stem tip). 

 Figure 4 shows a similar plant stripped down about 5 months after 

 application of NAA at 1,000 p.p.m. Note that from the time of appli- 

 cation the growth of the developing leaves was severely curtailed, 

 there was some damage to the leaf tissue, some rotting and root forma- 

 tion on the basal white leaf tissue, a marked constriction and elonga- 

 tion of the stem, and an unusual proliferation of roots for some dis- 

 tance up the stem. The constriction of the stem and the evidence of 

 disturbed growth in the leaves is eventually outgrown, and succeeding 

 leaves attain again the previous maximum length, provided the plant 

 is not induced to flower naturally or artificially. However, the total 

 mass of green tissue which must contribute to the fruit has been re- 

 duced much below that illustrated in Figure 3. Reduced plant size 

 generally means reduced fruit size, and when a standard can size for 

 sliced pineapple must be met, this is not acceptable. 



Quite apart from the commercial aspects, is the shortened leaf 

 an indication of an induced juvenility? There is some circumstantial 

 evidence in favor of this view. The leaves on 'Smooth Cayenne' pine- 

 apple are normally spineless except at the tip. (This is, of course, the 

 first tissue laid down in the growth of these monocotyledonous leaves.) 

 When excessive levels of NAA have been used (and incidentally also 

 when the plant resumes growth after a period of drought), some spines 

 may be produced on the leaves just below the area of constricted 

 growth. Parenthetically, it may be suggested that this is further evi- 



