Root aerobic respiration and growth characteristics of three Typha species in response to hypoxia

The responses of root aerobic respiration to hypoxia in three common Typha species were examined. Typha latifolia L., T. orientalis Presl, and T. angustifolia L. were hydroponically cultivated under both aerobic and hypoxic growth conditions to measure root oxygen consumption rates. Hypoxia significantly enhanced the root aerobic respiration capacity of the two deep-water species, T. orientalis and T. angustifolia, while it did not affect that of the shallow-water species, T. latifolia. T. angustifolia increased its root porosity and root mass ratio, while T. latifolia increased its root diameter under the hypoxic growth conditions. The relative growth rates in biomass of T. orientalis and T. angustifolia were 59 and 39% higher, respectively, under the hypoxic growth conditions than under the aerobic growth conditions. In contrast, that of T. latifolia did not differ between the two conditions. In T. orientalis and T. angustifolia, enhanced root aerobic respiration rates under the hypoxic growth conditions would have increased the nutrient uptake, and thus higher relative growth rates were obtained. For the deep-water species, T. orientalis and T. angustifolia, the root aerobic respiration capacity was enhanced, probably in order to maintain the generation of respiratory energy under hypoxia.