Fig. 5.

Porosity (% gas-filled volume per unit tissue volume) of four different tissues from adventitious roots: basal zone of root with secondary aerenchyma (1-cm segment taken 3 cm below root–shoot junction); mature zone of root (5–6 cm behind the root tip); root tips (1 cm); and root nodules of Melilotus siculus as affected by mineral nitrogen (N) supply (0 or 11 mm NO₃⁻) and drained or waterlogged conditions. Treatments were imposed 28 d after seed imbibition, for 21 d (plants were 49 d old when harvested) (20/15 °C day/night). Plants were grown in vermiculite and provided with a nutrient solution. Values are means ± s.e. (n = 3; one plant from an individual pot was partitioned to provide one replicate of the various tissues measured). For statistics see Table 3.