The Development of the Grain of Wheat

Abstract

A study during 1907 and 1908 of various plots of wheat cut at three-day intervals leads to the following general conclusions:(1) The whole plant, and with it the nitrogen, ash, and phosphoric acid it contains, increases in weight until about a week before it would be regarded as ready to cut. Some decrease of dry weight takes place during the last week.(2) In the formation of the grain three stages may be distinguished:(a) a period during which the pericarp is the most prominent feature,(b) the main period during which the endosperm is filled,(c) the ripening period characterised by the desiccation of the grain.(3) For the filling of the endosperm each plant possesses as it were a special mould, and continually moves into the grain uniform material cast in that mould, possessing always the same ratio of nitrogenous to non-nitrogenous materials and ash. The character of the mould possessed by each plant is determined by variety, soil, season, &c.(4) The main feature of the ripening process is desiccation rather than the setting in of such chemical changes as the conversion of sugars into starch, non-protein into protein, though the latter change also takes place.(5) The maximum dry weight of grain is attained a day or two before the grain would be regarded as ripe by the farmer. Allowing for the fact that the tillered shoots are a little behind the central shoots, no loss of weight in the crop will be incurred by cutting before the corn appears quite ripe, while a number of accidental mechanical losses due to birds, shedding, weather, may thus be avoided. Other experiments have shown that, though there may be no gain, there will be no loss in the quality of the wheat due to such early cutting.