Uptake and distribution of nitrogen in wheat plants supplied with different amounts of nitrogen after stem elongation

Abstract

SUMMARYThe uptake of nitrogen and its distribution between shoots and between organs within shoots in wheat (Triticum aestivum) was studied from the start of stem elongation to 28 days after anthesis in a glasshouse experiment with eight nitrogen levels between 0·1 and 12·8 mequiv./litre.There was no net uptake of nitrogen in plants supplied with 0·8 mequiv./litre or less; with more nitrogen the absorption increased linearly. Twenty to 44% of the total plant nitrogen was absorbed after anthesis, this fraction increasing with nutrient supply. The nitrogen allotted to the main shoot decreased until the onset of anthesis and increased thereafter at the expense of the tillers, except with 12·8 mequiv./litre, where nitrogen percentage in the main shoot decreased also after anthesis. Raising nitrogen supply increased the proportion of plant nitrogen recovered in the tillers.Nitrogen accumulated in the ear after emergence and by the 28th day after anthesis it contained between 52% and 73% of the total plant nitrogen. The ear of the main shoot had a higher proportion of shoot nitrogen than that of the tillers. The fraction of ear nitrogen supplied by retranslocation decreased from almost 100% with 0·8 mequiv. N/litre or less to nil with 12·8 mequiv./litre. Increasing nitrogen application decreased the fraction of total nitrogen allocated to the ear.