370 PLANT GROWTH SUBSTANCES 



acetic acid (CIPA), at 30 parts per million (ppni.) applied to the flower 

 clusters of 14 varieties compared with respective controls in altering the 

 pattern of production of field tomatoes is illustrated in Figure 2. Such 

 alterations in harvest intensities should help to avoid seasonal overloading 

 of markets. Peaks of production are leveled and the harvest time ex- 

 tended. The harvest pattern as illustrated for treated plants is more 

 desirable not only for the grower of fresh market tomatoes but for 

 processing as well. 



JULY AUGUST SEPTEMBER 



Figure 2. Comparative seasonal patterns of fruit production in hormone- 

 treated and control tomato plants. The harvest period is extended and peaks 

 of production are avoided when growth substances are used to overcome 

 delayed fruit set induced by cold night temperatures. 



An interesting and practical aspect of the effect of night temperatures 

 on tomato pioduction is the key it provides in enabling one to predict 

 when during the harvest season the price will break on the fresh market. 

 From the data that have been compiled, it appears that the time of the 

 first flush of tomatoes on the fresh market is predetermined by an ex- 

 tended period of night temperatures favorable for fruit setting in a 

 given area. These intervals of optimal temperature precede fruit ripening 

 by 45 to 50 days, the usual time necessary in Michigan for fruit to ripen 

 after it is set. In Figure 3 are given the average night temperatures 

 prevaihng during the month of June for the years ot 1947, 1948, and 



