The Utilization of Endosperm Reserves During Early Growth of Barley Cultivars and the Effect of Time of Application of Nitrogen

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Abstract
The cultivars Akka and Hiproly with high grain nitrogen and Julia and Foma with low grain nitrogen and Proctor containing high or low nitrogen were compared. The high nitrogen forms germinated more rapidly and by day 6 had a higher axis dry weight than the low nitrogen types. By day 6 dry weight of tops and roots was similar in the high nitrogen cultivars but that of the tops was less in the low nitrogen forms. Analyses of the partition of nitrogen from endosperm to axes confirmed that for all types this was maximal after 48 h from planting and occurred at a similar relative rate so that 50 per cent of the endosperm nitrogen was translocated by 84–96 h from planting. Loss of endosperm dry weight was much slower and here high nitrogen forms translocated dry matter at a significantly faster relative rate than the low nitrogen types. Nitrate supplied at planting or on day 2 increased the rate of endosperm depletion in the low nitrogen types and resulted in their achieving similar axis dry weights to high nitrogen forms which were largely unaffected by nitrate supply. Delay in nitrate application had progressively less effect on endosperm breakdown. There was a greater uptake of nitrate by the low nitrogen forms and rate of uptake was rapid. Uptake of nitrate by high nitrogen types was initially rapid but was followed by a much slower phase. The results indicate that endogenous and exogenous sources of nitrogen are equally suitable for seedling growth. The significance of grain nitrogen content in relation to endosperm breakdown is discussed as is the strategy of partition of endosperm reserves between root and shoot.

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