Studies had been carried out on the after-ripening of wheat grains during 1957 and 1958. The results obtained are summarized as follows:
1. During the period of after-ripening (1–2 month), determinations on the rate of respiration were made at intervals of one week, it indicated that the differences are not significant. The grains at different state of after-ripening (germination ranging from 2% to 99%) had similar oxygen consumption. The breakage of seed coat makes the gas exchange easily, which results to the end of after-ripening, as general beleived, seems questionable.
2. Take-off the pericarp only or together with the seed coat resulted an increase in percentage of germination for dormant grains, but the effect of this treatment was much significant as the grogress of after-ripening close to the end. It indicated that some biochemical changes should occurred during after-ripening, and the removal of seed coat enchanced these changes.
3. Treated the dormant grains with water solution of gibberellic acid increased the germination, but the same treatment inhibited it (table 6), when the grains had completed their after-ripening.
4. Pre-chilling the soaked grains at 4 ℃. for 2 days increased the percentage of germination, when they were translocated to 25 ℃. Determination on the sugar content indicated that both the total and reducing sugar were increased in around 100% than the check. The effect of pre-chilling seems that stimulated the growth of the embryo on the one hand and mobilized the reserve food on the other.
5. During the course of soaking (24 hours), the content of the deoxyribonucleic acid in the embryos of old wheat grains increased 29.4% (2905) and 36% (2419), but not for the grains either shortly after harvested or completed the after-ripening by artificial means.