Effect of Shading on Nonstructural Carbohydrates and their Turnover in Culms and Leaves during the Grain Filling Period of Spring Wheat1

The effect of light intensity on the content of nonstructural carbohydrates in leaves and culms and on grain yield of spring wheat ( Triticum aestivum L., ‘Kolibri’) was studied during the grain filling period. Light intensity was reduced by shading the plants with muslin after the onset of anthesis. At this time, the nonstructural carbohydrate present in highest quantity in the vegetative plant material was sucrose. Later the fructosans showed the highest concentrations in leaves and culms. In both treatments an accumulation of polysaccharides, particularly of fructosans, occurred in the culms during the first 2 to 3 weeks after anthesis, suggesting that at this stage of grain filling, net photosynthesis was higher than assimilate consumption for grain filling. The depletion of nonstructural carbohydrates at maturity was of a much higher order in the culms and leaves of the shaded plants while these parts in the control plants still contained a quantity of nonstructural carbohydrates which amounted to about 10% of the grain weight. Grain yield was about 20% lower in the shaded plants as compared with the control plants. The results conclusively show that fructosans are the most important storage carbohydrates in leaves and culms during grain filling. Mobilization of storage carbohydrates such as fructosans and starch is a major process which may limit grain production.