Miscellaneous Uses 303 



The means by which these auxin applications to pineapple can bring 

 about a decrease in apical dominance is obscure. 



OTHER USES 



It is interesting to note that the application of auxins to flowers 

 or fruits may cause either an abortion of the ovule (Swanson et al, 

 1949) or, contrariwise, an improvement of fertilization (Wester and 

 Marth, 1949). Some attempts have been made to utilize the beneficial 

 effects of auxin on fertilization in plant breeding procedures (Wester 

 and Marth, 1949), but the effects have not been consistent enough to 

 achieve widespread use. 



The influence of auxins in retarding abscission have been utilized 

 in the Christmas greens industry to prevent the abscission of leaves 

 and fruits of holly (Milbrath and Hartman, 1942). They also are 

 sometimes incorporated into insect sprays for orange trees to prevent 

 the leaf abscission which may follow (Stewart and Ebeling, 1946). 

 Again, when young friuts are frosted the retarded auxin transport 

 apparently makes the fruits prone to abscise, a situation which can 

 be prevented by auxin spray (Crane, 1954). An auxin antagonist such 

 as maleic hydrazide can be incorporated into a defoliation spray for 

 cotton and further encourage abscission (Hall et al, 1953). 



The property of auxins in producing epinastic curling of leaves 

 has been utilized by Franklin (1948) to facilitate the bolting of lettuce. 

 It seems that in head lettuce of some varieties the flowering scape is 

 unable to push its way through the leaves and consequently in lettuce 

 breeding work each head must be slashed with a knife to permit 

 emergence of the flowers. Auxins sprayed on the lettuce in some in- 

 stances produced an improved bolting, presumably because epinastic 

 curling of the leaves permited the scape to come through. 



A use of auxin in altering the crotch angle of trees has been re- 

 ported by Verner (1938). 



Lastly, 2,4-D has been found to be effective in killing back rag- 

 weed plants sufficiently to prevent pollen release in the autumn 

 (Smith et al, 1946). With the affliction of ha) fever so widespread, it 

 is curious that this technique has not become more commonly used. 

 Beginning in 1948 Canadian areas used as summer retreats by hay- 

 fever sufferers have fought l)ack the encroachment of ragweed by 

 2,4-D sprays particularly along roadsides. 



