Original paper

Vegetative and reproductive traits of Sagittaria trifolia (Alismataceae) in response to sediment heterogeneity and plant density

Zou, Yingying; Wang, Jinwang

Abstract

Changes in vegetative and reproductive traits of the emergent aquatic plant Sagittaria trifolia (Alismataceae) in response to sediment heterogeneity and plant density were investigated under two sediment treatments (homogeneous and heterogeneous) and three density treatments (10, 30, and 100 plants m-2 ). For the heterogeneous sediment treatment (He), an experimental bin was constructed with clay on the top layer and sandy loam on the bottom layer. For the homogeneous treatment (Ho), an equal mixture of clay and sandy loams was placed in both layers. The biomass accumulation per bin was not affected by plant density or sediment type; however, individual biomass was affected by both factors. The root-to-leaf ratio was only affected by density, whereas root distribution was only affected by sediment type. In the He treatment group, 54-56 % of the roots were located in the top layer. In contrast, the Ho treatment group had 52-53 % of the roots located in the bottom layer. Plants of S. trifolia produced male-biased floral sex ratios with flower numbers that increased in the later infl orescences. Moreover, the ratio of female to male flower production (F/M) increased signifi cantly with the infl orescence number. The relative allocation to sexual and asexual reproduction was 7 % and 60 % higher in the He treatment than in the Ho treatment, respectively. When plant density increased from 10 to 100 plants m-2, the relative allocation to asexual reproduction increased from 0.03 to 0.12, but the relative allocation to sexual reproduction decreased from 0.41 to 0.19, respectively. These data indicate that reproduction is shifted towards an asexual mode at higher plant densities. Our results suggest that S. trifolia can adjust its vegetative traits and reproductive strategy in response to plant density and sediment type. This hypothesis is consistent with the view that monoecy is a flexible sexual strategy for adjusting male and female allocation in various environments.

Keywords

aquatic plantreproductive allocationroot distributionsediment heterogeneityplant density