The Potential Pre-anthesis and Post-anthesis Contributions of Stem Internodes to Grain Yield in Crops of Winter Barley

Field experiments to assess the development of the main stem, its constituent internodes, and their potential contributions to grain yield in one cultivar of winter barley were carried out in four growing seasons. Internodes developed sequentially up the stem and all reached their maximum mass after attaining their final length. Lower internodes were the main potential contributors of pre-anthesis assimilate to grain-filling but upper internodes were an important source of stored assimilate accumulated after anthesis. If the contribution of stored assimilate to grain yield is equated only with the potential pre-anthesis contribution then the importance of the stem as a storage organ is grossly underestimated. The ratio of pre-anthesis to post-anthesis contribution to total storage ranged between years from 1:1·3 to 1:3·1. Crops that lost more mass from the stem also had greater grain yields. The stem is the major source of assimilate towards the end of grain-filling. Mass lost from the stem between the time of maximum stem mass and maturity can potentially account for 62% to 92% of the increase in grain mass during this period.