Architectural plasticity in response to population density in Abutilon theophrasti (Malvaceae)

Abstract

AbstractAn increase in population density may result in the spatial and temporal heterogeneity of resources at scales smaller than an individual, inducing different modular responses at different positions of a plant, or architectural plasticity. To better understand how plants respond to density via architectural plasticity, we conducted a field experiment on an annual species, Abutilon theophrasti. Plants were subjected to three densities and harvested at 50 and 70 days, when each individual plant was separated into different layers vertically from bottom to top with an inter‐layer distance of 10 or 20 cm, before we measured a series of traits per layer and analyzed variations in them among layers, densities, and stages. Increased density reduced variation of traits among layers and had different effects on different layers of modular traits: it increased stem mass in the third to fifth layers (L3–L5) and increased stem diameter in the top layer, leading to an increase in stem density in lower layers and a decrease in stem density in the top layer. In addition, there was an increase in petiole length and mass, lamina size, and leaf number in upper layers, while they decreased in lower layers. Results suggested trade‐offs between upper and lower layers in stem density and leaf traits for plants in a dense population, which were important for keeping most leaves at higher positions to acquire light resources, while saving energy, in concert with the effort of extra stem elongation and the complex plasticity in branch traits.