Whyte 



— 11 — 



Research in Vernalization 



tohormones affected the subsequent development of plants, what might be 

 called "vernalization by hormone." In some cases it was claimed that 

 the growth of the vegetative organs was either inhibited or accelerated ; in 

 others fructification was intensified and occasionally a conspicuous curtail- 

 ment of the vegetative period was recorded. Tiie whole question has how- 

 ever been experimentally investigated by Hatcher (1943) and Hatcher 

 and Gregory (1941) whose work is revievi-ed later. 



This work has completely negated the theory of Cholodny. As far as 

 the hormonal treatment of seeds is concerned, the balance of evidence is at 

 the moment against any after-effect of the above nature (Templeman, 1939 ; 

 Stewart and Hamner, 1942), although Hamner (1938) has referred to 

 a U. S. Patent being taken out by one Wendt for the application of acety- 

 lene to pineapple plants. Hamner states: "The prompt differentiation of 

 flower primordia and fruit development which ensue in treated plants as 

 compared with non-treated plants which differentiate flower primordia many 

 weeks and even months later is worthy of critical experimentation." 



In his book entitled "The physiological bases of winterhardiness in cul- 

 tivated plants," TuMANOV (1940) deals with the literature on a number 

 of aspects directly or indirectly related to developmental physiology, includ- 

 ing the relation between winterhardiness and phasic development as under- 

 stood in Russia. In the research of Vasiljev (1934), Kuperman (1936), 

 KuPERMAN and Zadoncev (1936), Saltykovskii and Saprygina (1935) 

 and others, it has been claimed that frost resistance is connected with phasic 

 development. These experiments were made chiefly with winter cereals ; frost 

 resistance was found to be generally lower, and at times conspicuously so, in 

 plants from vernalized seeds, that is, from seeds with embryos which had, as 

 far as could be ascertained, completed the thermo-phase, to use the terminol- 

 ogy of phasic development. The following percentage survival of wheat plants 

 observed by Tuma.nov (1935) is quoted as an example: 



Tumanov and Ivanova found that both early and late sowings of ver- 

 nalized grain of Lutescens wheat became depleted at higher temperatures 

 (-11 to -12°C.) than sowings from unvernalized grain, and that generally 

 the frost resistance was higher with the shorter periods of presowing 

 vernalization. After 20 days of vernalization of winter wheat and 15 days 

 in winter rye, the frost resistance of the resulting plants was conspicuously 

 reduced. 



Special investigations conducted in the Leningrad region indicate the 

 risks to which autumn sowings were exposed when the early autumn tem- 

 peratures favour the natural vernalization of seeds after sowing. When 

 Lutescens 0329, Moskov 0241 1 and Minhardy had been sown at the end of 

 August, they were found to have completed their thermo-phase on Jan. 13 



