There is variation
within the Brassica genus in the response of species to
waterlogging, including Brassica rapa (Ashraf and Mehmood,1990), and Brassica napus (Niknam and Thurling, 1995).
However, these differences are apparent even in the absence of
aerenchyma that improves gas exchange between the shoots
and roots in plants growing in waterlogged soils. Voesenek et al.
(1999) measured oxygen concentrations in the roots of B. napus
cultivars, as well as the radial oxygen loss from the roots and
concluded that the lack of aerenchyma development and the
high rate of leakage of oxygen from the roots contributed to the
inability of these plants to adapt to water logging. Overall,
members of the Brassica genus appear less tolerant of
waterlogging than many other plant species.