Whyte — 3 — Research in Vernalization 



brought into prominence a little of this historical background, stating that 

 "it seems only fair to point out that the basic concepts involved in these stud- 

 ies (on vernalization and developmental phases) have been known within 

 certain circles for many years. They simply have not been recognized in all 

 circles of plant science until recently." After stating that the older horti- 

 cultural and agricultural journals and the older scientific journals and text 

 books demonstrate that some growers and some botanists had already 

 recognized part or all of these concepts, McKinney refers to an early re- 

 port in 1857 by Klippart of Ohio, and even earlier records (20 years before 

 Klippart) of the production of a crop of grain from spring-sown winter- 

 wheat seed which had been subjected to low temperatures before sowing. 

 Klippart's statement is so much to the point that it is again quoted here 

 from McKinney. 



"To convert winter into spring wheat, nothing more is necessary than that the 

 winter wheat should be allowed to germinate slightly in the fall or winter, but kept 

 from vegetation by a low temperature or freezing, until it can be sown in the spring. 

 This is usually done by soaking and sprouting the seed, and freezing it while in this 

 state and keeping it frozen until the season for spring sowing has arrived. Only two 

 things seem requisite, germination and freezing. It is probable that winter wheat 

 sown in the fall, so late as only to germinate in the earth, without coming up, would 

 produce a grain which would be a spring wheat, if sown in April instead of September. 

 The experiment of converting winter wheat into spring wheat has met with great suc- 

 cess. It retains many of its primitive winter wheat qualities, and produces at the rate 

 of 28 bushels per acre." 



From these and similar examples, one can bring the discussion into mod- 

 ern times by reference to the classic experiments of Klebs and Gassner 

 which, as already noted, provided the starting point of the modern branch 

 of biological research concerned with developmental physiology. 



The work of Klebs was concerned with the control of growth and de- 

 velopment by appropriate adjustments of the decisive factors of the environ- 

 ment, temperature and light. Three developmental phases were recognized, 

 not all of the same nature. Ripeness-to-flower is a qualitative phase not 

 recognizable morphologically, and is dependent on the temperature effect 

 in relation to assimilation and dissimilation. The initiation of flower primor- 

 dia and the formation of inflorescences and flowers are quantitative phases, 

 recognizable morphologically. This research by Klebs and the postulation 

 of a form of phasic development contain at least a reference to most of the 

 problems at issue in the study of the developmental processes in plants, and 

 of the reasons for the transformation from a vegetative to a reproductive 

 state. He recognized the effect of the decisive factors, temperature, light 

 and/or darkness, alone or in combination, upon a series of phases or condi- 

 tions, each one of which must be established before the next can begin ; a 

 hint of an after-effect of light treatment; evidence of reversal of develop- 

 ment; the internal metabolic changes associated with vegetative growth or 

 reproductive development. 



Klebs was, however, primarily concerned with the effect of light. 

 Gassner (1918) was primarily interested in temperature, and temperature 

 only in the early stages of plant growth, just after germination. As Gassner 

 considered that the shooting and flowering of winter cereals depends to a 

 marked degree on their passing through a period of low temperature, ex- 



