Vernalization and Photoperiodism 



-34- 



A Symposium 



after anthesis, while the embryo is developing, and before the onset of dor- 

 mancy. 



A preliminary experiment was performed in 1935, when the ripening 

 ears were chilled by two methods : 



(1) The ears together with several nodes of the stem were cut off and kept in 

 water in a refrigerator for 5 weeks at 1°C. Control ears similarly treated were kept in 

 a dark room at normal temperature until the grain ripened off. After the low-tempera- 

 ture exposure the treated ears were allowed to complete ripening at room temperature. 



(2) The second method consisted in treating ears attached to the plant. The 

 selected ears after anthesis were inserted into wide glass test-tubes, plugged with cotton 

 wool. In one set these tubes were placed in the necks of vacuum flasks containing crushed 

 ice. The ears were thus kept at low temperature but did not come into contact with free 

 water. Control ears were similarly treated and placed in vacuum flasks but without 

 ice. After 24 days the ears were removed and allowed to ripen normally in the open 

 air. 



Oaus ^m anthesis to beginning oP treatment 



Illustration from Gregory and Purvis' classic 'Studies in the Vernalization of Cereals' (II, The 

 Vernalization of Excised Mature Embryos, and of Developing Ears, in Ann. Bot., N. S. 2, 5, 1938) 

 showing the relation between age of embryo at beginning of vernalization in the ear, and effective- 

 ness of the treatment (black := vernalized; white = unvernalized controls). 



The ripe grains obtained from plants thus treated in 1935 were sown 

 on March 17, 1936, in pots of sand, without further low-temperature treat- 

 ment. Flowering was irregular, especially in those plants resulting from 

 grain which had been treated in vacuum flasks, where the duration of the 

 treatment was less than that known to be optimal for vernalization, but 

 flowering was appreciably hastened by both methods of chilling and results 

 were sufficiently encouraging to warrant repetition of the experiment in the 

 following year, when longer periods of treatment were used. 



