Absorption, accumulation and distribution of manganese in winter wheat cultivated under super-high-yielding conditions

In order to clarify the characteristics of manganese (Mn) absorption, accumulation and distribution in winter wheat cultivated under super-high-yielding (≥9000 kg/ha) conditions, a field experiment was conducted in Gaocheng County, Hebei Province during 2004-2006. Six winter wheat cultivars, SM14, SM12, JF703 and SX828 during 2004-2005, and TM1, SM12, SX531 and SX828 during 2005-2006, were used as experimental materials. The growing area for each cultivar was 1 hectare, divided into three subplots of 3333 m2 as three replications. Plant samples were collected from the plots at each growing stage for Mn concentration determination in laboratory. The main results showed that, the concentrations of Mn in various above-ground organs of wheat ranged from 11.5 to 137.7 mg/kg. The concentration of Mn in leaf blades was always the highest among all organs during the growing period, with the order of leaf blade ≥ leaf sheath > stem > spike from pre-winter to the booting stage, while the order of leaf blade > spike≥ grain >leaf sheath≈ stem from the anthesis to maturity stages. Among all above-ground organs, the highest accumulation amounts of Mn were in leaf blades during early growing period, but in grains during late period. The accumulation amounts of Mn in the whole plants of all cultivars were increased with growing process, and reached to the maximum values 865.5-1350.0 g/ha during ten days after anthesis to maturity. The accumulative percentages of Mn by wheat plants were about 12%, 80%, and 100% of the total accumulation at pre-winter, anthesis and maturity respectively. During the pre-booting period, the Mn absorbed by wheat plants was mainly distributed in leaf blades and sheaths, especially in blades, where the distribution percentage was higher than 50%. At maturity, however, the distribution percentage of Mn in spikes was higher than 50%, which was higher than those in other organs. The phasic and daily absorption amounts of Mn by wheat plants during their growing periods were all in double peak curves. The first peak with a lower peak value occurred before winter, and the second with a higher peak value occurred during the middle growing period from the double ridge to anthesis. These results demonstrate that, pre-winter and middle growing periods are the key periods of Mn absorption by super-high-yielding winter wheat. The supply of Mn for these key absorption periods should be satisfied by presowing seed soaking or mixing and foliar application during the middle growing period.