Turion production and nutrient reserves in Potamogeton crispus are influenced by sediment nutrient level

Abstract

The influence of sediment nutrient content on asexual propagule production in plants is poorly understood, especially in submersed macrophytes. To improve the understanding of turion (an aboveground asexual propagule) production, Potamogeton crispus L. was planted in 2 experimental conditions that differed in their levels of sediment nutrients. After 10 wk of growth, sediment nutrient level had significantly impacted the plants' vegetative and reproductive traits. Most vegetative trait measures of P. crispus (e.g. leaf mass fraction and stem mass fraction) were higher when plants were grown in nutrient-rich sediment compared with plants grown in nutri- ent-poor sediment. Reproductive trait measures (e.g. turion mass fraction and individual turion biomass) were higher in plants grown in nutrient-poor sediment compared with plants grown in nutrient-rich sediment. Plants grown in nutrient-rich sediment produced a larger number of small turions ( 100 mg) and stored more total nonstructural carbohydrate (the major proportion of which was starch) in them. Path analysis revealed that total plant biomass (strong positive effect), leaf and stem biomass (weak negative effects) had direct effects on total turion biomass, which consequently affected turion size and number. Moreover, ramet number and mean shoot height also had weak but direct effects (both negative effects) on turion size and number. These results demonstrate that sediment nutrient content mediates plant vegetative traits and can subsequently affect turion production and reserves in P. crispus.