Sulfhydryls-A new factor in frost resistance. V. Direct measurements on proteins and the nature of the change in SH during vernalization of wheat

Abstract

1. Protein SH (as % of SH + 2 SS) in the soluble protein of vernalizing wheat was determined in two ways: (1) Protein SH was taken as equal to supernate SH. Protein SS was obtained by subtracting the SS of non-proteins (after Sephadex separation from the proteins) from supernate SS. (2) Protein SH and SS were measured directly on the proteins after Sephadex separation from the non-proteins. 2. Using method 1., % protein SH paralleled all five changes in frost resistance during a 35-day vernalization in each of two winter wheats (Kharkov and Minhardi). 3. Using method 2., % of protein SH paralleled all five changes in frost resistance during a 35-day vernalization of a spring wheat (Thatcher). 4. Method 1. failed to show the parallel in the case of Thatcher, method 2. failed in the case of Kharkov and Minhardi. 5. The changes in % protein SH were due to SH ⇄ SS oxidation-reduction in Thatcher. In Kharkov and Minhardi this was also involved, but during the more pronounced changes in frost resistance, the protein SH changes were apparently due to a splitting off or adding on of non-protein SS. 6. The parallel between % of protein SH and hardiness in Thatcher is apparently an artifact that arises due to oxidation during the Sephadex separation. This indicates that the more frost resistant the grain, the less readily the protein SH is oxidized to SS during the Sephadex separation.