Abstract
AimsRoot aerenchyma, a key adaptive trait to anoxic soils has rarely been integrated into trait-based plant ecology. This study aims to evaluate the relationship between root porosity and root economics-related traits among wetland plants, focusing on the effect of aerenchyma on root tissue density, a central trait in plant economics spectrum.MethodsRoot porosity, root tissue density with air-space included (RTD) or excluded (RTDA), and other root traits such as root dry matter content (root dry mass to fresh mass ratio) were measured separately for adventitious and lateral roots of 16 garden-grown Ontario wetland monocots with contrasting root longevities.ResultsPrincipal component analysis showed that in the root adaptive trait space of wetland plants, the first dimension is defined by economics-related traits, the second dimension by lateral root porosity and the ratio of lateral to adventitious root length, and the third dimension by adventitious root porosity. Interspecific variation in root porosity was unrelated to root economics traits. Consequently, root tissue density excluding air space (RTDA) better differentiated between species with contrasting root longevities than RTD did, consistently both for adventitious and lateral roots. Root dry matter content accurately predicted RTDA.ConclusionsInterspecific variation in root porosity is independent of root economics: Wetland plants can construct economically conservative or acquisitive roots of any porosity. Consequently, to consistently express root functional relationships among wetland plant species, root tissue density should be expressed with excluding the air space (i.e., RTDA), or with the more easily measured root dry matter content.
Highlights
Root economics spectrum (RES), based on morphological and physiological root traits that are associated with resource acquisition and resource conservation, has been suggested to match the aboveground leaf economics spectrum (Mommer and Weemstra 2012; Reich 2014; Roumet et al 2016)
A principal component analysis showed that in the root adaptive trait space of wetland plants, the first dimension is defined by economics-related traits, the second dimension by lateral root porosity and the ratio of lateral to basal root length, and the third dimension by basal root porosity
Interspecific variation in the aerenchyma content is independent of root economics: Wetland plants can construct economically conservative or acquisitive roots of any porosity
Summary
Root economics spectrum (RES), based on morphological and physiological root traits that are associated with resource acquisition and resource conservation, has been suggested to match the aboveground leaf economics spectrum (Mommer and Weemstra 2012; Reich 2014; Roumet et al 2016). Traits such as specific root length (SRL), root respiration rate, root tissue density (RTD) and root life span have been shown to co-vary across species and biomes, enabling their potential use to form a synthetic spectrum to represent root economics, i.e., patterns of allocation and turnover of carbon and nutrients (Ryser 1996; Roumet et al 2016; Liu et al 2016; Han and Zhu 2020). The applicability of RES may be ecosystem-dependent, depending on the specific below-ground constraints the plants are subjected to in a given ecosystem (Shipley et al 2016; Carvajal et al. 2018), and, a functional RES may require the use of more specific traits (Poorter and Ryser, 2015; McCormack et al 2017)
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