Whyte — 37 — Research in Vemalization 



Harlan and Pope with barley (1922, 1926) that ears removed from the 

 plants as early as 5 days after fertilization produce viable grain. 



Conclusion: — It has been seen that research on the biological pro- 

 cesses concerned in vernalization has almost reached its limit in the mean- 

 time, particularly in the very detailed studies of Gregory and Purvis. Until 

 their hypothetical precursor has been isolated and its nature defined, strik- 

 ing advances in this direction are not to be expected. 



Neither does it appear probable that the method of vernalization will 

 itself become widely used, except possibly in those districts in countries such 

 as the U.S.S.R. or India where conditions of drought or flood make a 

 difference of a few days in maturity a desirable objective. In countries 

 not experiencing extreme conditions, the low-temperature treatment will 

 not be used when superior genotypes can be found, and would therefore 

 be confined to genetical or similar research, or in the production of market 

 garden crops if a few days' earliness means increased economic return. 



The greatest economic significance of this research appears to be, how- 

 ever, in the two incidental discoveries which have been made, namely, the 

 possibility of vernalization before seed ripening and of devernalization and 

 revernalization according as conditions favour one process or the other. 

 Vernalization of developing embryos while still attached to the mother 

 plant is an important factor in the selection of areas for seed production, and 

 in plant introduction and the moving of seeds from one environment or lati- 

 tude to another. Early strains may become late, and vice versa. 



Devernalization also affects a number of agronomic questions, as in many 

 environments a temporary period of high temperature may partially or 

 completely annul any degree of vernalization already achieved naturally in 

 the field. Waterlogging of a field in a wet winter might also be expected to 

 produce the anaerobic conditions found to favour devernalization ; seeds in 

 a heavy clay soil may possibly be more liable to devernalization through 

 anaerobic conditions than those in light well-aerated soils. 



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