226 Auxins in Agriculture 



Shortening of Time to Maturity 



The fact that fruit growth may be started by forcing with auxin 

 even before a flower is opened (figure 94) demonstrates one way in 

 which auxin appHcations may shorten the time to harvest. A second 

 way is the commencement of fruit growth 3 or 4 days sooner by auxin 

 appHcation than by pollination. Such earlier growth can be seen in the 

 data of Roberts and Struckmeyer (1944) and of Singletary (1950). This 

 may be because the time required for the release of the natural auxin- 

 producing mechanism which follows pollination is eliminated when 

 the auxin is added directly. Data from greenhouse experiments indi- 

 cate that the use of auxins can cause production of mature tomato 

 fruits approximately six days earlier than would occur naturally on the 

 first flower cluster (Singletary, 1950). 



The ability of auxin treatments to produce mature fruit in less 



100 MG/L 



CONG. OF AUXIN 



Fig. 96. The effects of various concentrations of auxin (p-chlorophenoxyacetic 

 acid) upon the subsequent fruit-set and numbers of fruits harvested. The work was 

 done with field-grown tomatoes (data of Mann and Minges, 1949). 



