Physiological Phenomena at the Time of Flowering.

Abstract

In order to study the growth curve of wheat, and especially the physiological phenomena at the time of flowering, Hard Federation wheat was grown in sand cultures under constant conditions. The illumination was continuous (Mazda C lamps), the temperature varied 1 to 2° C., the relative humidity of the air varied about 10 per cent, the water and salt content in the sand was kept as constant as possible. Every two days 6 plants were harvested and the freshweight and dry-weight of every leaf, stem and ear was determined in every plant separately. Each plant had 5 leaves and 1 stem with ear at maturity (all the tillers were removed as soon as they started to grow). These experiments quite confirmed the results which Kreusler 1 obtained with corn some fifty years ago. He found that the gain in dry-weight was minimum at the time of fertilization of the ears or the first development of the kernels. However, recalculation of his results and of the data of several other investigators shows a close correlation between the time when this minimum occurred and the time when 100 per cent female inflorescences were present, i. e., the week during which the maximum number of female inflorescences flower. In our experiment with wheat the minimum occurred exactly at the time of stamination.

This recalculation shows, furthermore, that coinciding with the minimum gain in dry-weight, there was also a minimum gain in fresh-weight or water (fresh-weight minus dry-weight). This minimum is not due to the fact that less dry-weight was gained during that period because the gain of water per gram dry-weight gainzd, (gain water)/(gain dry-weight), also showed a marked minimum.