Properties of root water transport in canola (Brassica napus) subjected to waterlogging at the seedling, flowering and podding growth stages

Abstract

The objective was to clarify the role of root water transport in waterlogged canola plants. We examined the hypothesis that waterlogging triggers root suberization and lignification, which reduces the effectiveness of apoplastic bypass and increases the dependence of roots on the aquaporin-mediated water transport, and that this effect varies depending on the growth stage. Brassica napus plants at the seedling, flowering and podding growth stages were waterlogged for up to 8 days. Growth, gas exchange, leaf water potentials, and root hydraulic conductance were measured in addition to relative contributions of the aquaporin-mediated and apoplastic root water transport, gene expression levels of plasma membrane intrinsic proteins (BnPIPs), and lignin and suberin deposition in roots. Waterlogging decreased dry weights, gas exchange, leaf water potentials and root hydraulic conductivity more in plants at the seedling stage than other growth stages. It also accelerated root suberization and lignification resulting in an increase of a relative contribution of aquaporin-mediated water transport. The transcript levels of BnPIPs increased with an increasing duration of waterlogging. Effects on root water transport played an important role in the sensitivity of canola seedlings to waterlogging. Increased relative contribution of aquaporin-mediated water transport in waterlogged plants was accompanied by enhanced root suberization and lignification. The evidence points to the importance of maintaining functional aquaporins in plant survival of waterlogging.