Morphological plasticity in response to emergence time and population density in Abutilon theophrasti (Malvaceae)

Increased density and delayed emergence are two major biotic factors in nature that have profound and complex effects on plants. No studies have attempt to compare the responses of plants to the two factors via morphological plasticity, particularly in dynamic patterns. We subjected plants of Abutilon theophrasti to four emergence times and three planting densities and measured and analyzed a number of mass and morphological traits at different growth stages. Across both stages, plants emerged in late spring had the highest total mass, and spring and late-spring plants had higher stem mass allocation than later germinants, but plants with delayed emergence had higher leaf and reproductive mass allocation, more leaves and less lateral roots, but lower stem length, stem and root diameter than early-emerged plants. Plants at high density performed lower in total mass and most other traits, but performed better in stem allocation and length, with shorter petioles and lateral roots, than at ..., Experimental design - Two field experiments were conducted in 2007, at the Pasture Ecological Research Station of Northeast Normal University, Changling, Jilin province, China (44°45’ N, 123°45’ E). We collected seeds of A. theophrasti from the small local wild populations near the research station in late August 2006. Seeds were dry stored at -4oC till using for experiments. We tested effects of emergence timing (ET) and population density (PD) on plants in two experiments respectively. The soil conditions of experimental field in the growth season of 2007 were the same as that in former studies: aeolian sandy soil (pH = 8.3) with nutrients availability of organic C 3.1 mg kg–1, available N 21.0 mg kg–1, and available P 1.1 mg kg–1.
For effects of emergence timing, we divided the whole plot into twelve 2 × 3 m sub-plots, which were randomly assigned with four ET treatments and three replicates per treatment. Seeds were grown at an inter-planting distance of 10 cm on June 7, June 27, Ju..., ,