title: Oxygen absorption by adventitious roots promotes the survival of completely submerged terrestrial plants.
abstract: Background and Aims Flooding imposes stress upon terrestrial plants because it results in oxygen deficiency, which is considered a major problem for submerged plants. A common response of terrestrial plants to flooding is the formation of aquatic adventitious roots. Some studies have shown that adventitious roots on submerged plants are capable of absorbing water and nutrients. However, there is no experimental evidence for the possible oxygen uptake function of adventitious roots or for how important this function might be for the survival of plants during prolonged submergence. This study aims to investigate whether adventitious roots absorb oxygen from the water column, and whether this new function is beneficial to the survival of completely submerged plants. Methods Taking Alternanthera philoxeroides (Mart.) Griseb. as a representative species, the profiling of the underwater oxygen gradient towards living and dead adventitious roots on completely submerged plants was conducted, the oxygen concentration in stem nodes with and without adventitious roots was measured, and the growth, survival and non-structural carbohydrate content of completely submerged plants with and without adventitious roots was investigated. Key Results Oxygen profiles in the water column of adventitious roots showed that adventitious roots absorbed oxygen from water. It is found that the oxygen concentration in stem nodes having adventitious roots was higher than that in stem nodes without adventitious roots, which implies that the oxygen absorbed by adventitious roots from water was subsequently transported from the roots to other plant tissues. Compared with plants whose adventitious roots had been pruned, those with intact adventitious roots had slower leaf shedding, slower plant mass reduction, more efficient carbohydrate economy and prolonged survival when completely submerged. Conclusions The adventitious roots of A. philoxeroides formed upon submergence can absorb oxygen from ambient water, thereby alleviating the adverse effects of oxygen deficiency, enabling efficient utilization of carbohydrates and delaying the death of completely submerged plants.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.|Department of Systems Ecology, Faculty of Earth and Life Sciences, Institute of Ecological Science, Vrije Universiteit, Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands and.
authors.forename: Qiaoli
authors.initials: Q
authors.lastname: Ayi
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zeng
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.
authors.forename: Jianhui
authors.initials: J
authors.lastname: Liu
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.
authors.forename: Siqi
authors.initials: S
authors.lastname: Li
authors.affiliation: Center for Environmental Sciences, Leiden University, Einsteinweg 2, 2333 CC Leiden, The Netherlands.
authors.forename: Peter M
authors.initials: PM
authors.lastname: van Bodegom
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Beibei, Chongqing 400715, PR China.
authors.forename: Johannes H C
authors.initials: JHC
authors.lastname: Cornelissen
keywords: 
            Alternanthera philoxeroides (Mart.) Griseb.; aquatic adventitious roots; microelectrode; oxygen uptake; submergence tolerance