296 Auxins in Agriculture 



sprayed during the early stages of fruit growth with /?-naphthoxy- 

 acetic acid (Zielinski and Garren, 1952). Incidentally, it is interesting 

 to note that the responsive stage in the growth of the strawberry is 

 one in which the natural auxin production is low (Nitsch, 1950). 



It is a little confusing to find that in some instances the applica- 

 tion of auxins at the time of fruit-set may actually retard the growth 

 rate. For example, Crane (1948) found that indolebutyric acid would 

 set fig fruits and retard the growth rate. The same fruits sprayed with 

 2,4,5-T respond in quite the opposite way as figure 122 showed. 



A hastening of maturity has been reported for apple (Gardner 

 et al, 1940), peach (Southwick, 1946), seedless grapes (Weaver and 

 Williams, 1951), prune (Zielinski et al, 1951), and apricot (Crane and 

 Brooks, 1952). The opposite effect on maturity, a delay, has been 

 reported for pineapple (Clark and Kerns, 1943), lemon and other 

 citrus fruits (Stewart, 1949). As already mentioned fig has been 

 reported to be sometimes hastened and sometimes delayed in maturit). 

 Associated with the hastened maturity there is usually no gain in 

 fruit size found for the apple or the peiuh, hut in each ol the othei 

 instances gains in size were obtained. 



TIME 



Fig. 122. The hastening of growth and maturity of Calimyrna figs by 2,4,5- 

 trichlorophenoxyacetic acid (25 mg./l.) applied to young fruits (Crane and Blon- 

 deau, 1949). 



