Whyte — 7 — Research in Vernalization 



found that the time required for the completion of some of the recognizable 

 stages in the growth of cereals such as seedling emergence, ear emergence, 

 full flowering, wax ripeness, etc., are completed more rapidly at higher 

 temperatures than at lower. It was noted, however, that in spring and 

 more especially in winter forms the phase of shooting (ear formation and 

 elongation of internodes) does not always show this relation. With an 

 increase in the temperature at which the crops are grown, this phase is in 

 some cases initiated earlier, and in others takes place later or not at all. 

 When absent, the plants remain at the tillering or rosette stage. Lysenko 

 called this retention of the winter habit "hibernalism," that is, the property 

 of plants to remain for an indefinitely long period at the phase of tillering 

 without flowering stems. 



After moving from Azerbaidzan to the Institute of Plant Breeding and 

 Genetics, Odessa, Lysenko continued to study, in collaboration with 

 DOLGUSIN. this propertv of hibernalism in cereals and the nature of the 

 dilTerence between spring and winter forms. The results of the experiments 

 carried out for this purpose were presented at the All-Union Congress of 

 Genetics, Selection, Seed Production and Animal Production in 1929 

 (DoLGUsiN and Lysenko, 1929), and may be indicated from the following 

 quotation of their conclusions : 



(o) Experiments on time of sowing showed that there are no definite dates which 

 can be used to distinguish winter forms from spring forms. The later the date of 

 sowing, the larger is the number of varieties which retain the winter habit ; when varie- 

 ties are sown in the second half of April, or even later under the conditions of 

 Azerbaidzan, not only all the winter and alternative forms but also the majority of the 

 spring forms remained at the tillering stage. 



(b) One of the main factors preventing shooting is the high temperature of the 

 period subsequent to sowing. However, after a pre-sowing chilling of slightly sprouted 

 or imbibed grain at 2.5 to 3.5° C. for a definite period varying according to variety 

 ( Kooperatorka wheat = 38 days; winter barley = 28 days), winter cereals will pro- 

 ceed to the shooting stage no matter when sown. After such a pre-sowing treatment, 

 the rate of shooting increases according as the temperature of the period following 

 sowing itself increases. Since a high temperature after sowing retards shooting in 

 plants raised from unchilled grains, it is argued that in cereals the period from seed 

 swelling to ear emergence covers at least two biologically consecutive phases. The 

 first of these does not produce any morphological changes in the plant and is direct^ 

 related to the thermal factor, high temperatures prolonging its duration. (Compare 

 with the condition of ripeness-to-flower postulated by Klebs, 1918). The duration 

 of the second phase (shooting) is, like all other phases, inversely related to tempera- 

 ture, progressing most rapidly at the higher temperatures. 



(f) Thus, the retardation of shooting observed in cereals sown without pre-treat- 

 ment and subjected to a high temperature after sowing is due to the prolongation of 

 the unrecognizable phase ; if the temperature of the period after sowing reaches a 

 maximum at and beyond which this phase for a given variety camiot be passed, then 

 this variety will behave as a winter form, and will not ear. 



((/) Since the temperature of the environment rises with the approach of summer, 

 it is observed in sowings of a mi-xture of varieties that the later the sowing, the greater 

 is the number of varieties which change from a spring to a winter habit. 



Having worked out a thermal constant for a number of varieties, Lysenko 

 and his associates at Odessa proceeded to apply this particular method of 

 chilling to slightly sprouted grain of cereals and seeds of other crops. In 

 1931 and 1932, Lysenko published instructions for the treatment of seed 

 by this method (jarovizacija) which came to be known in countries other 



