Whyte — 33 — Research in Vernalization 



Study in collaboration with Dr. B. P. Pal, Imperial Economic Botanist, of 

 the vernalization response of all the available strains of Indian wheats in 

 his collection. A report will shortly appear in a joint paper with B. P. Pal 

 of the results of vernalizing ISO strains of Indian wheats. Though an 

 earliness of agricultural significance in ear emergence of certain cultivated 

 Indian wheats can be obtained by the use of vernalized seeds, it is found 

 that the number of tillers, the factor positively correlated with yield, is 

 smaller. Trials on closer spacing in sowings are therefore being made. 



Response to Temperature Before Seed Ripening: — The discovery 

 reported independently by Kostjucenko and Zarubailo in Russia and 

 Gregory and Purvis in England that the low temperature effect associated 

 with vernalization can be obtained on ripening seeds while they are still 

 attached to the mother plant has made it desirable to give careful considera- 

 tion to the environment, and particularly to the temperatures experienced 

 before harvest. 



Kostjucenko and Zarubailo (1935, 1936, 1937) laid down a trial of 

 winter wheat varieties at the Polar Experimental Station of the All-Union 

 Institute of Plant Industry (VIR) at Hibiny. The grain used had been 

 grown in two widely diiifering environments, namely, Hibiny itself (N. Lat. 

 67°44') and Kirovobad (N. Lat. 40°41'). In both sowings vernalized and 

 unvernalized grains were used. In September of the sowing year it was 

 seen that the plants grown from these grains of different origin were distinct 

 in their behaviour. Plants from Kirovobad grain artificially vernalized were 

 then at the milk-ripe stage, while those from unvernalized Kirovobad grain 

 were at the tillering stage. On the other hand, plants from Hibiny grain 

 also artificially vernalized were almost at the stage of wax ripeness, while 

 plants from the same grain not artificially vernalized exhibited partial or 

 complete flowering; some of the latter had set seed in the ears of the main 

 stem. 



Thus, these Russian varieties of wheat, generally regarded as winter 

 forms, behaved as spring forms when grown from grain which had ripened 

 at Hibiny, but retained their winter habit when grown from Kirovobad 

 grain. Kostjucenko and Zarubailo conclude that the Hibiny grains 

 had been able to pass their "stage of vernalization" or thermo-phase under 

 the natural conditions of these northern latitudes, while the Kirovobad 

 grains had not done so and still required artificial vernalization before they 

 could reach maturity in one season after being sown in spring. It was as- 

 sumed that the embryos of the Hibiny grain were vernalized by low tempera- 

 ture while still attached to the mother plant. An embryo which has not en- 

 tered the dormant state may be sensitive to vernalization in the same degree 

 as one which has been brought from the resting non-reactive condition by 

 soaking. The details of these and other experiments by these Russian in- 

 vestigators are discussed more fully elsewhere (Whyte, 1946)- 



After their experiments on the vernalization of excised embryos, 

 Gregory and Purvis (1936&, 1938ffl) proceeded independently to study the 

 effect of vernalization on developing embryos and immature ears. Having 

 shown that the vernalization process occurred in the embryo apart from 

 the endosperm, it appeared possible to apply the low-temperature treatment 



