Water level-dependent morphological plasticity in Sagittaria montevidensis Cham. and Schl. (Alismataceae).

Gr Demetrio,Ff Coelho,Mea Barbosa

doi:10.1590/1519-6984.26912

Abstract

Aquatic plants are able to alter their morphology in response to environmental condition variation, such as water level fluctuations. The aim of this study was to evaluate the effect of water level on Sagittaria montevidensis morphology through measures of vegetative structures formed in drought and flood periods. We hypothesised that the plant height and the biomass of S. montevidensis leaves will increase during flood periods, while the biomass and diameter of petioles, and the basal plant area will increase during dry periods. We sampled a total amount of 270 individuals in nine sediment banks per visit, totalling 1080 plants. In order to compare plant morphology between dry and flood periods, we measured the water level in each bank and took the following variables for each plant: diameter, height and diameter of the biggest petiole. In order to compare biomass allocation between dry and flood periods, we sampled a total amount of 90 individuals in nine sediment banks per visit, totalling 360 plants. Plants were dried and weighed in the laboratory. All measured morphologic traits, as well as the biomass of leaf blades and petioles, were higher during flood periods, indicating that water level highly influences the morphology of S. montevidensis individuals. Our results suggest that these morphological responses allow survival and maintenance of S. montevidensis populations under environmental stress. These results can be linked to the invasive potential of S. montevidensis and sheds light on basic management practices that may be applied in the future.

Highlights

Aquatic plants are known for having great phenotypic plasticity, which can be defined as the organism’s ability to alter its physiology or morphology in response to environmental variation (Schlichting, 1986)
Changes in water level are cited as powerful inducers of plastic responses in aquatic macrophytes (Trémolières, 2004), but growth responses to flooding may be species-specific (Deegan et al, 2007; Luo and Xie, 2009) and, in the case of our study, S. montevidensis strongly responded to water level fluctuations between drought and flood periods
Increases in height of submerged parts of emergent macrophytes, as well as a higher biomass allocation to the aerial parts, are commonly adopted as growth strategies to deal with water level increase (Grace, 1989; Clevering and Hundscheid, 1998; Sánchez-Reyes et al, 2012)

Summary

Introduction

Aquatic plants are known for having great phenotypic plasticity, which can be defined as the organism’s ability to alter its physiology or morphology in response to environmental variation (Schlichting, 1986). Plasticity in morphological traits can be decisive for plant survival, especially in the case of aquatic plants that can suffer submersion with the variation in water levels (Webb et al, 2012) Structures such as leaves and petioles can suffer changes in number, length, biomass and diameter in response to environmental variations, such as water level fluctuations (Cassol et al, 2008). Major key life-history traits that suffer morphological changes enhancing the survival of such plants include: tissues elongation, new leaves recruitment, petioles and basal plant diameters, and emergent surface area (Cooling et al, 2001; Deegan et al, 2007; Iwanaga and Yamamoto, 2008; Xie et al, 2008; Li et al, 2011). Biomass allocation patterns can be modified during flood periods, and plants usually invest more in aerial parts when water level is increasing (Lowe et al, 2010; Chagas et al, 2012; Pan et al, 2012; Zhang et al, 2012; Tian et al, 2013)

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