Effects Of Nitrogen Appliction On Dynamic Characteristics Of Selenium Uptake, Translocatong And Distribution In Wheat

Nitrogen application is one of the most important measures for increasing crop yield in agriculture, but impact of nitrogen application on accumulation, translocation and distribution of selenium in winter wheat at different periods is not clear. A pot experiment was carried out to study effect of nitrogen application on selenium accumulation of winter wheat at different growth periods for providing theoretical reference of reasonable nitrogen application and increasing selenium content of grains. Wheat was grown under greenhouse conditions with low(Se 0.81 mg/kg) or high(5.02 mg/kg) levels of selenite, and low(Se 0.74 mg/kg) or high(2.60 mg/kg) levels of selenate, and each Se treatment was supplied with 100 mg/kg or 200 mg/kg nitrogen. Selenium concentrations and biomass amounts of different parts of wheat were determined at 7 stages of seedling, jointing, booting, heading, flowering, filling and maturity. The selenium contents of wheat in different treatments and the selenium absorption rates of roots at different growth periods were analyzed, and the influence of the nitrogen application on selenium accumulation, translocation and distribution in wheat with the same selenium level was investigated. The main results are as follow:1. The wheat yields under both the low and high Se treatments are increased by 21.7% and 13.7% with the high N supply, respectively. The Se contents in the grains and glumes under the high N and low Se supplies are 31.2% and 13.6% higher than under the low N and low Se treatment, and those in high N and high Se condition are 13.2% and 17.8% lower than the low N and high Se condition, respectively.N levels can affect various organs Se enrichment factor of wheat, at low Se treatments, N promote enriched Se on spike and old leaves, while at high Se treatments antagonistic. Se difficult to transport from wheat stems roots, but more easily from the stems and leaves to the grain. High N promote Se transport to the shoots at vegetative stage, and promote Se transport from leaf to grain and husk at low Se treatments, whereas it mainly to promote Se transported to the glume at high Se treatments at reproductive growth stages of wheat.2.In selenate conditions, grain yield increased with increasing nitrogen levels were 13.2% and 24.0% at low selenium and high selenium treatment, respectively, and decreased root biomass, relieved of selenium toxic of wheat seeds at high Se treatments. Regardless of N,Se content of wheat increased with Se concentration increasing(P<0.01).Increasing nitrogen application promote leaf wheat, grains and root uptake Se, the promoting at low Se greater than the high Se treatments, grain Se contentions increasing with the concentration of N increased by 22.6% and 12.1% at low and high Se treatment, respectively.Se enriched in wheat shoots mainly, increasing N can promote Se-enriched wheat in various organs, especially in the leaves and grains, but the promotion of transport processes did not reach significant levels.3.Selenate and selenite absorption characteristics are less the same in wheat. The rate of Se absorption are fastest between seedling and jointing stage of wheat, More than 90 percent of Se absorbed before flowering stage in wheat, wheat also have a faster absorption between jointing and booting stage.Se percentage in the spike increased with wheat’s growth. At maturity, the proportion of Se in the spike about 1/5 and 1/3 at selenate and selenite treatment, respectively.4. With N content increasing, the Se absorption amount and proportion distribution in root were decreasd, on the contrary, spike and grain at selenate treatments; increasing N fertilization increases the distribution ratio of Se in grains by 11.1% and 25.9%, at low and high selenate tratments. At selenite condation, the proportion of Se in roots under the high N is about a quarter lower than the low N, increasing N fertilization increases the distribution ratio of Se in grains by 18.4% at low selenite treatments,decreases the ratio about 8.0% at high selenite treatments.The Se levels in each parts of wheat vary with growth periods and the Se of soil, and the N application promote the accumulation, translocation and distribution of selenium in wheat. High nitrogen fertilization could promote uptake and translocation of Se in wheat under low Se conditions soil, and improve Se use efficiency as well in the agricultural production.