Applied nitrogen and seed nitrogen effects on growth of barley (Hordeum vulgare L.) seedlings prior to emergence: importance of water uptake

For barley (Hordeum vulgare L.) prior to emergence from the substrate, addition of 5 mollm3 nitrate (N03) or 5 mol/m3 chloride (Cl) to a nitrogen (N) free but otherwise complete nutrient medium resulted in decreased residual seed dry weight (d.wt) and increased shoot+ root d.wt 14- 21 days after sowing (DAS). Increased seedling growth with additional N03• or Cl was associated with increases in shoot+ root and residual seed anion content, total plant water and residual seed water content (% water). Seedling growth rate was greater for high N content seed than for low N content seed. This effect was associated with greater seed water content in high N seed from 2 DAS onwards. Additional N03• did not affect residual seed water content until 14 DAS. The effects of seed Nand N03• on seedling growth were detected 10 and 14 DAS respectively. It is proposed that the increased seedling growth rate with additional N03 is due to an increased rate of mobilisation of seed reserves caused by increased seedling water uptake, while the seed N effect on seedling growth is due to increased water uptake by the seed directly.