Whyte — 17 — Research in Vernalization 



to a gradual shortening of the vegetative phase, vi'hich asymptotically ap- 

 proached a limiting value. This occurred in winter oats (var. Eckendorfer) 

 after 80 days treatment, in mustard after 50 days vernalization. The Hmit- 

 ing duration of the vegetative phase after optimal duration of vernalization 

 was dependent upon the daylength under which the plant was grown ; being 

 minimal in continuous light, maximal in short days. The extension of day- 

 length leads in both plant types to a gradual shortening of the vegetative 

 phase, and again approaches a limit value. The limiting duration of the 

 vegetative phase under optimal photoperiod is dependent upon the duration 

 of vernalization. 



The leaf number on the main shoot of oats is directly related to the 

 development, as McKinney and Sando showed for wheat, and Purvis and 

 Gregory for Petkus winter rye ; the same direct relation between leaf num- 

 ber and time of flower formation was established also in Sinapis alba. The 

 results can be interpreted without difficulty along the lines of the flower 

 hormone h3'pothesis of Purvis and Gregory. 



RuDORF, Stelzner and Hartisch (1937) described a technique for 

 vernalizing seed at high temperatures, presumably for use with crops such 

 as soybeans. The aim in this work was to prevent fungal and bacterial 

 growth and to avoid excessive elongation of the seedling. It is necessary 

 to keep the seed in motion and at the same time to maintain the tempera- 

 ture and moisture in the seed containers within the desired limits ; a cer- 

 tain amount of aeration must be practicable and it must be possible to 

 darken the whole apparatus. A portable apparatus is described, movement 

 being secured by the use of small disinfection drums. 



Germany is a borderline environment as far as the cultivation of soy- 

 beans is concerned, yet the wide range of products that can be obtained from 

 this crop made it desirable to grow it wherever possible. Experiments have 

 therefore been made on the manipulation of development of this crop. 

 RosENBAUM (1937a, 1937b) attempted to vernalize soybeans; although 

 agreeing that the conditions of treatment laid down by Lysenko are prac- 

 tically correct, it is considered that similar effects may be attained with other 

 temperatures, and that, by suitable adjustment of the conditions of growth 

 and development, the vernalization treatment may be dispensed with en- 

 tirely. The environmental conditions following sowing are stated to govern 

 the course and rate of development more than does previous vernalization, 

 for which reason it is considered to be difficult to make reliable comparisons 

 of the results of vernalizing different varieties. A reduction in time taken 

 to flower may be more readily obtained by means of the photoperiodic after- 

 effect, although this is said to entail a reduction in yield. Rosenbaum does 

 not recommend either vernalization or photoperiodic induction of soybeans 

 for the use of the practical farmer or the plant breeder in Germany. 



Another German worker who does not consider that a thermo-phase is 

 obligatory in winter wheat is Voss (1938). By using short day under con- 

 ditions of a constant high temperature of about 20° C., it was found possible 

 to induce shooting in German winter wheats. The manner in which a variety 

 reacts to treatment may differ within the variety under (a) combined 

 cold and short-day treatment, and (b) short-day treatment alone, at 

 high temperatures. Given a very long growth period, winter wheat 



