374 PLANT GROWTH SUBSTANCES 



and humidity in both Missouri and Michigan, hormone sprays and dusts 

 of CIPA and CIPP have given 10-25 per cent yield increases. Most of 

 the increase in yield has been accounted for by larger fruit size rather 

 than an increased set. This observation is in agreement with the recent 

 work of Randhawa and Thompson (36). Fisher et al. (14), however, 

 reported an increase due to the production of more pods rather than 

 larger ones. Unfortunately, in snap beans precise information is lacking 

 as to the exact temperature and humidity requirement for optimal fruit 

 set. From a practical standpoint growth substances could be profitably 

 used on snap beans as a type of insurance against low yields induced by 

 unpredictable adverse weather. Consistent increases in yield of a sig- 

 nificant magnitude and a hastening of maturity even under weather 

 conditions favorable to pod development should further the use of 

 growth substances in the production of snap beans. 



Some of the more disappointing studies to date on the use of growth 

 substances for improving fruit set have been with lima (7,50) and dry 

 shell (11) beans. The hormonal stimulation of ovarian tissue adjacent 

 to the seeds in tomatoes and snap beans resulting in increased fruit 

 production has generally been observed to depress rather than to stimu- 

 late seed formation. When growth substances are used in a manner similar 

 to those employed for improving fruit set in tomatoes and snap beans, 

 they are likely to be ineffective on crops wherein yields are measured 

 in terms of seed production, such as peas, lima beans, dry shell beans, 

 and so on. 



General Considerations. — A series of recent reports on the fig, with 

 possible fascinating implications for other fruits, have been published 

 (6,9,10,44). The possibility through growth substances of not only 

 controlling fruit set but also its time of maturity as well in fruits other 

 than the fig and, as has been reported previously, in the pineapple (48), 

 should attract interest and stimulate research in this possible role of 

 the plant growth hormones. 



Some interest has been focused on possible alterations of nutritional 

 values in fruits (tomatoes and snap beans) when induced to set by the 

 use of growth substances. Variations in nutritional values have not been 

 great nor of sufficient magnitude either to encourage or discourage the 

 use of growth substances as fruit-setting sprays on the basis of their 

 improvement or impairment of nutritional or market quality of the 

 resulting produce (19,22,35,36,38,55,57). Supplementary to these in- 



