Effects of Cu Pollution on the Expansion of an Amphibious Clonal Herb in Aquatic-Terrestrial Ecotones.

Liang Xu,Zhen-Feng Zhou,Jian Liu

doi:10.1371/journal.pone.0164361

Abstract

Physiological integration can enhance the performance of clonal plants in aquatic and terrestrial heterogeneous habitats and associated ecotones. Similar to nutrients, pollutants may be transported among connected ramets via physiological integration. Few studies have examined the expansion of amphibious clonal plants from terrestrial to aquatic environments, particularly when the local water supply is polluted with heavy metals. A greenhouse experiment was conducted using the amphibious plant Alternanthera philoxeroides to determine whether Cu can spread among clonal plants and examine the corresponding effects of this pollution on the expansion of clonal plants in aquatic-terrestrial ecotones. Ramets from the same clonal fragments were rooted in unpolluted soil and polluted water at five different levels. The responses of the ramets in terrestrial and aquatic habitats were quantified via traits associated with growth, morphology and Cu accumulation. The results indicated that ramets in soil and water significantly differed in nearly all of these traits. The expansion of populations from terrestrial to polluted aquatic habitats was facilitated by stem elongation rather than new ramet production. The accumulated Cu in polluted ramets can be horizontally transported to other ramets in soil via connected stolons. In terms of clonal growth patterns, variations in Cu pollution intensity were negatively correlated with variations in the morphological and growth traits of ramets in polluted aquatic habitats and unpolluted soil. We concluded that Cu ions are distributed among the clones and accumulated in different ramet tissues in heterogeneous habitats. Therefore, we suggest that Cu pollution of aquatic-terrestrial ecotones, especially at high levels, can affect the growth and expansion of the whole clones because Cu ions are shared between integrated ramets.

Highlights

Many exotic invasive plants are clonal species, and clonal growth characteristics, such as physiological integration are associated with the ability of plants to adapt to foreign environments, compete with local plants and colonize associated habitats [1,2,3,4]
We addressed the following questions: (1) How do the ramets of plants expand in heterogeneous habitats, and do the growth, morphological and Cu accumulation traits vary among habitats? (2) To what extent do pollutants affect the phenotypic plasticity of plants and the functional correlations between adaptation and expansion? (3) How does the plasticity of growth, morphological and Cu accumulation traits vary in response to pollution stress? To achieve our objectives, the seedlings of Alternanthera philoxeroides, a common amphibious invasive species with clonal growth traits, were used to simulate the invasion of plants from terrestrial to aquatic environments at different pollution intensities
Ramets rooted in soil had larger growth rates for both stem elongation (GL) and new ramet production (GNR) than those rooted in water for each of the six growth periods (Table 1; Fig 3A and 3B), which resulted in longer total stem lengths and consistently broader occupation in terrestrial habitats (Table 1; Figs 2A and 3)

Summary

Introduction

Many exotic invasive plants are clonal species, and clonal growth characteristics, such as physiological integration are associated with the ability of plants to adapt to foreign environments, compete with local plants and colonize associated habitats [1,2,3,4]. Cu Pollution Affects Expansion of an Amphibious Clonal Herb facilitates the survival and growth of new ramets in stressful heterogeneous environments and improves the performance of the entire clone [9,10,11]. Certain clonal invasive plants are amphiphytes [12,13,14]. During the entire life cycle, clonal growth assists these plants in resisting heterogeneous stress and expanding populations between terrestrial and aquatic habitats [14,15,16,17]

Methods

Results

Discussion

Conclusion