Studies on the Harm by Shading on Wheat and Barley : VII A consideration of the diurnal variation of the NH₄-N absorption, especially in relation to the sunshine. : VIII The effect which shading at different periods exerts on the growth and yield of wheat and barley

Abstract

1) The diurnal variation of the NH₄-N absorption was observed especially in relation to the sunshine. It was found that the maximum absorption occurred at the 18∼22 hour period and minimum at the 2∼6 or the 6∼10 hour period. When the time lag between the beginning of the sunshine and the beginning of the NH₄-N absorption was observed, it was found to be about 6hours. It seems that this is because it takes time before the carbohydrate produced iu the leaves begins to benefit the nourishment absorbing function of the root. A clear explanation can be obtained when the diurnal variation is considered in this light. 2) Which shading treatment af different periods of growth influenced the growth and yield of wheat and barley most was observed. It was found that shading at different periods did damage to the yield in different degrees and that the structure of decreased yield varied. The yield decreased by the shading at the period when successful panicles appeared because the number of panicles decreased and at the period of the developing and maturing of the reproductive organ because the number of the grains decreased due to the hindrance in the ripening process. It may be added that there was a certain period when no harm by shading was observed and when greater yield could be expected by checking the unsuccessful panicles