The Study Of Phosphorus On Rice Selenium Uptake

Selenium is one of the essential microelements for humans and animal. Selenium deficiency in humans may suffer from various diseases. Many regions lack of selenium. Rice is the staple food of our country. It is an ideal way to increase the selenium content of rice in order to supplement the human selenium nutrition. Because rice long-term grows in flooded environments, roots form red-brown iron plaque. Iron plaque affects many elements absorption. Phosphate fertilizer, as the crop essential abundance element, easily accumulates in the soil. The interaction between phosphorus and selenium can directly affect the adsorption and desorption of selenium in the soil, transport and transformation as well as distribution in rice. In order to clarify the effect of phosphorus on rice selenium uptake, these studys were carried out that the simulation experiments of effect of phosphorus on adsorption and desorption of selenium, the culture experiments of the interaction of phosphorus and selenium, the effect of phosphorus on rice uptake selenium in the presence of iron plaque and the interaction of phosphorus and selenium at different pH.The main results were as follows:(1) Through the simulation experiments, effect of phosphorus on purple soil selenium absorption and desorption was cleared. The results show that soil solution pH from 3 to 9, the adsorption capacity of purple soil on selenium was reduced. HPO42-can reduce the absorption of SeO32- in purple soil, and significantly increased selenium desorption rate.(2) Through the hydroponic and the soil culture experiments, the effect of phosphorus on rice selenium absorption and transport was cleared. The results show that phosphorus concentration from 0 to 0.293 mmol L-1, the content of selenium in shoots and roots significantly reduced, however, continuing to increase phosphorus concentrations, selenium content in shoots and roots was no longer reduced. Phosphorus at low concentration (P<1.707 mmol L-1), increasing phosphorus concentrations promoted rice selenium transportation from roots to shoots and at the high concentration (P>1.707 mmol L-1) this phenomenon was suppressed. With the increase of phosphorus, the enrichment of selenium in rice roots and shoots was increased. On the soil culture experiment, the treatment of high phosphorus high selenium increased grain yield. At high selenium treatment, with the increase of phosphorus, the selenium transition from shoot to panicle was inhibited and Selenium content in spike was reduced.(3) Through the hydroponic experiment, the effect of phosphorus on iron plaque formation of root and rice selenium uptake was cleared and the relationships of iron plaque, phosphorus and selenium were confirmed. The results show that when phosphorus deficiency and Fe2+ presence, reddish-brown iron plaque appeared on root surface. When reducing phosphorus concentration, iron plaque quantity increased, selenium content of roots and shoots decreased and the transfer coefficient of selenium from the root to shoot decreased. In the presence of iron plaque, the selenium content in the DCB and roots was increased, however, the selenium content in shoots was decreased. Phosphorus from 0.1 to 0.3mmol L-1, the selenium content in DCB was reduced, but shoots was increased. When the absent of iron plaque, increasing phosphorus concentration promoted the transfer amount of selenium from the root to shoot. In the presence of iron plaque, when the phosphorus from 0 to 0.1 mmol L-1, selenium transfer coefficient was increased, however, the phosphorus from 0.1 to 0.3 mmol L-1, selenium transfer coefficient was reduced.(4) Through adjusting different pH, the interactions of iron plaque, phosphorus and selenium were studied. The results show that pH significantly affected the content of selenium in shoots and roots, the content of selenium in shoots at the pH5 was highest, while the content of selenium in the root at the pH3 was highest. Iron plaque inhibited shoots Se uptake, but the effect on selenium in the root was not significant. Phosphorus significantly promoted the shoots Se uptake. When pH from 3 to 8, the distribution rate of Se in the shoot first increased and then reduced, however, in the roots first decreased and then increased.