Determining the dynamic responses of cotton root morphological characteristics under waterlogging stress using the minirhizotron technique

Roots are important in plant adaption to waterlogging stress. Zero-day (control), 8-day (moderate) and 14-day waterlogging (heavy) stresses were applied on lysimeter-grown cotton plants at flowering. The dynamics of total root length, root surface area, root volume and root number were traced using the minirhizotron technique. The results showed that the rapid root morphological growth period of non-stressed cotton occurred from the early squaring stage to the mid-late flowering stage. The two waterlogging treatments significantly stimulated root morphological growth compared with the control, but the stimulatory effect occurred more than 23 days after waterlogging termination. The stimulatory effect of heavy waterlogging stress was stronger and lasted longer than that of moderate waterlogging. The stressed cotton root system shifted its morphology centre from the upper soil layers (0-24 cm) to the deep layers (24-60 cm). Waterlogging stress obviously stimulated the morphological growth of roots with diameters <2.0 mm (especially those with diameters <1.0 mm) but had little impact on thicker roots. These results provide references for cotton adaptation under waterlogging stress.