302 Auxins in Agriculture 



dominance is also removed and lateral shoots commence growth. This 

 undesirable second growth has been controlled with auxins and with 

 oils applied to the severed tip. More recently, maleic hydrazide has 

 been found to prevent the growth of lateral suckers (Naylor and 

 Davis, 1950; Grant, 1953). The effect is not a modification of apical 

 dominance but rather a direct inhibition of growth. The maleic hy- 

 drazide treatment has the advantage of being an overall plant spray, 

 whereas the auxin or oil treatments must he placed carefully on each 

 severed stem tip. 



An undesirable side effect from the use of auxins in forcing pine- 

 apples to flower is the increased apical dominance which occurs in the 

 plants. This is expressed as a reduction in the number of slips and 

 suckers developing on the peduncle and stem of the forced plant. Be- 

 cause slips and suckers are the planting material for the pineapple 

 crop, the loss of such lateral bud development can become a severe 

 economic liability. Clark and Kerns (1943) reported that naphthalene- 

 acetic acid which had been sprayed on young fruits to increase fruit 

 size had a remarkable effect in increasing the number of slips and 

 suckers as shown in figure 125. The more detailed researches of Whang 

 (1948) have indicated that chlorophenoxyacetic acid applied approxi- 

 mately five days after flower forcing with naphthaleneacetic acid 

 results in consistent gains in the number of slips and suckers obtained. 



1000 MG/L 



CONG. OF AUXIN 



Fig. 125. The effects of naphthaleneacetic acid in increasing numbers of lateral 

 buds (slips and suckers) in the pineapple plant (Clark and Kerns, 1943). 



