Linking oxygen availability with membrane potential maintenance and K + retention of barley roots: implications for waterlogging stress tolerance

Oxygen deprivation is a key determinant of root growth and functioning under waterlogging. In this work, changes in net K + flux and membrane potential ( MP ) of root cells were measured from elongation and mature zones of two barley varieties under hypoxia and anoxia conditions in the medium, and as influenced by ability to transport O 2 from the shoot. We show that O 2 deprivation results in an immediate K + loss from roots, in a tissue‐ and time‐specific manner, affecting root K + homeostasis. Both anoxia and hypoxia induced transient membrane depolarization; the extent of this depolarization varied depending on severity of O 2 stress and was less pronounced in a waterlogging‐tolerant variety. Intact roots of barley were capable of maintaining H + ‐pumping activity under hypoxic conditions while disrupting O 2 transport from shoot to root resulted in more pronounced membrane depolarization under O 2 ‐limited conditions and in anoxia a rapid loss of the cell viability. It is concluded that the ability of root cells to maintain MP and cytosolic K + homeostasis is central to plant performance under waterlogging, and efficient O 2 transport from the shoot may enable operation of the plasma membrane H + ‐ ATP ase in roots even under conditions of severe O 2 limitation in the soil solution.