Analysis of growth components in roots of wheat seedlings exposed to low O₂ concentrations

Root growth was analysed in 6 to 8-day-old seedlings of wheat (Triticum aestivum L.) during exposure to low O₂ concentrations by measuring the length of epidermal cells at fixed points along the root axis. The effect of O₂ deficiency on cell elongation and cell production was inferred from estimates of cell length and the rate of root extension. Epidermal cells ceased elongating at a point 6 mm from the root tip. The rate of cell elongation reached a maximum between 1 and 2 mm from the apex, and the position of this zone was independent of O₂ concentration. The final length of epidermal cells and the total number of cells displaced from the elongating zone per hr (cell flux) were reduced by 20 and 44%, respectively, in roots grown to 0.055 compared with 0.115 and 0.26 mM O₂ (aerated solution). In roots exposed to 0.01 mM O₂, cell degeneration was evident in apices after 48 hr, presumably due to a lack of ATP required for maintenance of membrane structure and solute transport.