Partitioning of Dry Matter and the Deposition and Use of Stem Reserves in a Semi-dwarf Wheat Crop

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Abstract
An experiment was carried out within a crop of spring wheat (cv. Condor) to examine dry matter partitioning between the developing stem and ear, and to estimate the magnitude of carbon stored in the stem both before and after anthesis, and the subsequent utilization of these reserves during grain growth. The amount of reserve laid down and mobilized was estimated from analysis of data for changes in masses of stem and leaf from frequent harvests. The rate of change of the dry mass of the individual plant organs was expressed as a proportion of the rate of change of the total dry mass of the large culm. This value was called the Allocation Ratio (AR). It was assumed that assimilate was transferred directly from the stem into the growing ear, and not into other organs. This paper provides evidence for the idea that the stem intemodes of wheat are able to accumulate and subsequently mobilize a dry matter reserve. The accumulation and subsequent mobilization of fructans in the stem was demonstrated using ascending thinlayer chromatography. On a dry matter basis the large culms of the wheat crop accumulated all of their stem reserves after anthesis (0–41 g per large culm; 98·4 g m−1). After adjusting the loss of mass by 33% to allow for respiration, it was concluded that post-anthesis stem reserves may have contributed at least 21% of the final grain yield of this crop.