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In the course of an investigation into the effect of nitrogenous fertilisers on the growth and yield of cereal crops, it was observed that lodging is often the limiting factor in attaining maximal yields by increased nitrogen supply. This is particularly the case under the humid conditions prevailing in the Netherlands during the greater part of the growing season of the cereals. Although for the production of high grain yields some bending over of the ripe plants is desirable, severe lodging both from the point of view of grain formation and of harvesting is unprofitable. In order to learn the circumstances under which lodging occurs, a number of field and pot experiments with rye, wheat, barley and oats have been carried out from 1940 to 1949. In most of the field experiments nitrogen dressings have been combined with applications of other nutrients and with variations in rate of seeding and in spacing. Although many papers have dealt with the problem of lodging, there is considerable disagreement amongst various authors as to its cause. The first investigators who studied this phenomenon came to the conclusion

The mechanism of nitrate reduction in fungi and higher plants has been cleared up by Nason and E v a n s 3 8 and Nicholas and Nason 1 1 . In experiments with purified cell-free extracts they found that the nitrate->nitrite reaction is catalyzed by an enzyme with either flavin adenine dinucleotide (FAD) or flavin mononucleotide (FMN) as the prosthetic group and moreover molybdenum as a constituent. Reduced dior triphosphopyridine nucleotide (DPNH or TPNH) are required as electron donor. The reduction sequence was established to be as follows