Whyte — 5 — Research in Vernalization 



It can thus be seen that, in the period before the technique of vernaliza- 

 tion was evolved and received such publicity, research workers in several 

 countries were concerned with this type of study and had proceeded a cer- 

 tain distance in the direction of controlHng growth and development by the 

 manipulation of the environment. Progress was being made in the Soviet 

 Union as well, where Maximov continued the experiments of Gassner and 

 treated seedlings with low temperature, thereby influencing the whole of 

 their further development. Winter cereals which, when sown in spring, did 

 not normally reach the heading stage, headed and flowered normally when 

 the seedlings had been exposed to a short period of chilling. It was found 

 possible to direct or determine the further course of development by treat- 

 ing them during the early stages of growth with appropriate temperatures 

 and a given periodicity of light. Although these experiments provided a 

 basis for understanding the behaviour of winter varieties in the field when 

 sown in autumn in the normal way, the technique was still, however, ap- 

 plicable chiefly to laboratory trials and crop cultivation in greenhouses, 

 owing to the fact that the treatment was applied to seedlings, which could 

 not be handled on a bulk basis like seeds. 



ToLMAcEV (1929j came even nearer to the development of a technique 

 which could be used in agronomic practice. His aim was to keep the seeds 

 in the form of seeds for as long a period as possible, and yet at the same 

 time to break their dormancy and permit growth to start very slowly. This 

 was presumably done because it was considered that the temperature dur- 

 ing or just after germination is the effective factor in inducing subsequent 

 flowering, and at the same time to provide treated grains, not seedlings, 

 which might still be sown in the normal manner. Working on winter wheat, 

 for example, Tolmacev applied partial soaking to retard growth during 

 germination ; by keeping such seed for 2 months at 0°C., he obtained plants 

 which produced ears in the first year when sown in spring, even after the 

 latest date of sowing. Similar results are claimed with sugar beet, and 

 conversely, it is stated that a sugar beet plant can be maintained in a vegeta- 

 tive condition for at least 4 years by withholding that factor of the environ- 

 ment (temperature) appropriate for development. 



To explain these results, practically identical with the results of ver- 

 nalization described below, Tolmacev produced what Maximov has de- 

 scribed as a "peculiar theoretical interpretation." According to Tolmacev, 

 winter cereals will not ear nor will sugar beet flower until a definite active 

 phase has been completed in their "stem plasm," a delinite work niuct b^.- 

 done and a sufficient amount of the products of disintegration accumulated. 

 In spring plants, the stem plasm is ready for its function at the time of seed 

 maturity. Those conditions, for instance, low temperature, which stimulate 

 the accumulation and preservation of the products of distintegration, also 

 stimulate fruit bearing, and on the contrary the absence of the accumulation 

 of the products of disintegration during intensive growth under the influ- 

 ence of light and high temperatures depresses stalk formation. 



U.S.S.R.: — Working at the Experiment Station at Ganja in Azer- 

 baidzan, Lysenko observed the influence of the thermal factor on the dura- 

 tion of the developmental phases in cereals and cotton (1928). It was 



