Studies have suggested that increased root hydraulic conductivity in mycorrhizal roots could be the result of increased cell-to-cell water flux via aquaporins. This study aimed to elucidate if the key effect of the regulation of maize aquaporins by the arbuscular mycorrhizal (AM) symbiosis is the enhancement of root cell water transport capacity. Thus, water permeability coefficient (Pf ) and cell hydraulic conductivity (Lpc ) were measured in root protoplast and intact cortex cells of AM and non-AM plants subjected or not to water stress. Results showed that cells from droughted-AM roots maintained Pf and Lpc values of nonstressed plants, whereas in non-AM roots, these values declined drastically as a consequence of water deficit. Interestingly, the phosphorylation status of PIP2 aquaporins increased in AM plants subjected to water deficit, and Pf values higher than 12 μm s-1 were found only in protoplasts from AM roots, revealing the higher water permeability of AM root cells. In parallel, the AM symbiosis increased stomatal conductance, net photosynthesis, and related parameters, showing a higher photosynthetic capacity in these plants. This study demonstrates a better performance of AM root cells in water transport under water deficit, which is connected to the shoot physiological performance in terms of photosynthetic capacity.
Keywords: aquaporins; arbuscular mycorrhizal symbiosis; cell hydraulic conductivity; cell pressure probe; photosynthesis; protoplasts; water permeability.
© 2019 John Wiley & Sons Ltd.