Absorption,accumulation and distribution of boron in high-yielding winter wheat

A field experiment was conducted in Gaocheng County,Hebei Province during 2005-2006.Four winter wheat cultivars,TM1,SM12,SX531 and SX828,were used as experimental materials.The growing area for each cultivar was 1 ha,divided into three subplots of 3333 m~2 as three replications.Plant samples were collected from the plots at each growing stage for boron(B)concentrations determination in laboratory.The main results showed that,the concentration of B in above-ground organs of wheat ranged from 1.15 to 9.56 mg/kg,with the order of leaf bladespikeleaf sheathstemgrain.The concentration of B in leaf blades and sheathes firstly increased from pre-winter to jointing stage,then decreased from jointing to anthesis,and then increased again during post-anthesis and reached peak at matu- rity.The accumulation amounts of B in leaf blades were consistently higher than other organs throughout all growing stages.The (?)ccumulation amounts of B in leaf blades increased before booting stage,but decreased after booting until maturity.The accumulation amounts of B in other organs and the whole plants were generally increased with growing pro- cesses.The accumulative percentage of B of wheat plants was 5%,10%,30%,40%,50% and 100% of the total ac- cumulation at pre-winter,double ridge,jointing,booting,anthesis and maturity stage respectively.The accumulation in- tensity of B during late growing period(anthesis to maturity)was the highest,while it was the lowest during early growing period(seedling emergence to double ridge).The total accumulation of B in above-ground organs of wheat during its life span was 59.72-78.83g/ha,which was mainly distributed in leaf blades and sheathes from pre-winter to jointing stage.The distribution rate of B in leaf blades decreased after booting stages,but the percentage in leaf blades was al- ways the highest among all above-ground organs during the whole growing period.This character of B distribution might be beneficial to high photosynthetic ability during middle and late growing period,and therefore,provide the basis of dry matter production for higher grain yield of wheat.