Maize cob plus husks mimics the grain sink to stimulate nutrient uptake by roots

To differentiate the impacts of grains (reproductive tissues) and cob plus husks (vegetative tissues) on biomass accumulation, nitrogen (N), phosphorus (P), and potassium (K) uptake and their distribution within maize plants, six Chinese maize varieties with different yield potentials released in last 60 years were employed in a two-year field experiment. Ears were either covered or removed at silking, the dry weight (DW) and NPK contents at silking and maturity in major sink organs of plants were closely observed. In comparison with control plants, covering ears reduced, and removing ears further decreased total DW and NP gains of whole plants, regardless of the larger root size and reduced shoot:root DW ratio. Since the total DW and NP gains of the new maize varieties after silking were more than that of the old varieties, the decrease of the total DW and NP gains caused by pollination-prevention and removing ears were also more in the new varieties. The uptake and distribution patterns of NP and K in maize plants were different. Developing grains and cob plus husks differentially reduced net post-silking K loss. The results suggested that the amount of nutrient uptake was not decided by the root size itself. Developing maize grains enhanced nutrient uptake rate of roots. The cob plus husks could partially substitute for grains as a strong nutrient sink to stimulate NP uptake by roots and reduce K loss from plants. (C) 2012 Elsevier B.V. All rights reserved.