Aims The aim was to reveal the effects of flooding on photosynthesis and growth of the riparian plant Salix variegata for revegetation of riparian areas in Three Gorges Reservoir Region.
Methods Four flooding treatments were applied to the plants: no flooding, belowground submergence and whole plant submergence to water depths of 0.5 and 2 m. Net photosynthetic rate, apparent quantum yield, carboxylation efficiency, intercellular CO2 concentration and maximal photochemical efficiency of PSII (Fv/Fm) were determined at 0, 40, 60 and 90 d. The numbers of adventitious roots were determined at 6, 15, 25 and 32 d. Increase of stem length, increase of number of shoots, number of newly grown leaves on stem, number of shed leaves on stem, increase of root biomass and increase of plant biomass were determined at 10, 20, 40, 60 and 90 d.
Important findings Control and belowground-submerged plants maintained high net photosynthetic rate, apparent quantum yield and carboxylation efficiency during inundation. At 40 d, the net photosynthetic rate of S. variegata was significantly higher than that in the waterlogging-tolerant species S. babylonica (p<0.05). At 60 and 90 d, the photosynthetic capacity andFv/Fm of wholly submerged plants decreased significantly as compared with that of the control and belowground-submerged plants (p<0.05), but the plants could still maintain high photosynthetic capacity. At 40, 60 and 90 d, the intercellular CO2 concentration of wholly submerged plants was higher than that of the control and belowground-submerged plants. At 32 d, many adventitious roots were developed in belowground-submerged plants, while the wholly submerged plants had few adventitious roots. The belowground-submerged plants had greater increase in stem length, number of shoots, and newly generated leaves on stem, root biomass and total plant biomass than wholly submerged plants. During the flooding period, the stem length, number of shoots, and newly generated leaves on stem, root biomass and total plant biomass of wholly submerged plants increased, and the number of shed leaves of wholly submerged plants was higher than that of the control and belowground-submerged plants. At 90 d, all belowground-submerged and wholly submerged S. variegata were alive. Therefore, S. variegata has high photosynthetic capacity and growth adaptability over inundation of 90 d and is a promising species for revegetation of the riparian zone in the Three Gorges Reservoir Region.