XVI International Botanical Congess

Roots are prone to soil flooding but are generally intolerant of anoxia. Shoot systems can suffer indirectly from soil flooding because of an inhibition of root functioning imposed by lack of oxygen. For example, water shortage arising from a depression of root hydraulic conductivity. The inevitable loss of foliar hydration can be minimized by root signals that promote stomatal closure and leaf epinasty. Partial oxygen shortage increases tolerance of roots to an anaerobic environment by promoting (i) metabolic adjustments and (ii) lysigenous aerenchyma created through positionally-directed programmed cell death. In submerged plants, a source of oxygen for transport through the aerenchyma is secured by a stimulation of upward shoot extension towards aerial oxygen.