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 m2 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 blade spike leaf sheath stem grain. 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 maturity. The accumulation amounts of B in leaf blades were consistently higher than other organs throughout all growing stages. The accumulation 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 processes. The accumulative percentage of B of wheat plants was 5%, 10%, 30%, 40%, 50% and 100% of the total accumulation at pre-winter, double ridge, jointing, booting, anthesis and maturity stage respectively. The accumulation intensity 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 59.7278.83 g/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 always 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.