The responses of root functional traits of submerged plant Vallisneria natans to substrate type and planting density and its relationship with individual growth performance

; Root functional traits reflect the growth status of plant fine roots and their adaptability to external environment. However, the time stability of root functional traits in response to environmental changes is still unclear. Vallisneria natans is a pioneer species for submerged vegetation restoration in water bodies. Fine roots play an important role in the early stage of population development. In this study, four growth substrates (straw pad, straw pad + sand, straw pad + yellow mud, and straw pad + sediment) and two planting densities (100 and 200 plants/m) were designed to simulate different substrates and densities in natural habitats. The functional traits of V. natans were sampled and measured in different periods. Two-way ANOVA with repeated measures was used to analyze the effects of time, substrate, density and their interactions on functional trait. Linear fitting models were used to investigate the relationship between root functional traits and growth performance (biomass allocation, nutrient uptake and individual colonization) in response to varied substrates, densities and periods. The results revealed that all measurement indicators were significantly affected by substrate, and some root functional traits such as root shoot ratio (RSR), root dry weight, specific root length (SRL), root specific surface area (SRA), root tissue density (RTD), root anchoring force and root volume were significantly affected by density. The biomass allocation was mainly affected by substrate, and the absorption, transportation and root fixation of nutrients were affected both by substrate and density. The linear fitting model revealed that SRA, RTD, root diameter, root surface area, and root volume could predict the responses of RSR to environmental changes at the individual level, with the best prediction using RTD. RSR, SRA, root number, total root length, root surface area, and root volume could partly predict the response of SRL to environmental changes at the individual level, with the best prediction using root number. SRA, root diameter, root surface area, and root volume could predict the response of root anchorage force to environmental changes at the individual level to a certain extent with the best prediction using SRA. However, the influence of substrate and density on the functional traits of V. natans roots may change significantly over different time periods. When we use root functional traits to predict growth performance at the individual level, the period of population reconstruction needs to be considered. © 2024 Science Press. All rights reserved.