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 lower densities. In competition for resources, plants will prefer stem elongation to leaf/root growth, and even at the cost of reproduction to ensure the survival of the present generations when competition is intense or lethal. By contrast, plants will prefer the investment into leaf and reproductive growth to stem/root growth, for offspring persistence, when shortened lifetime does not threaten the contemporary survival. The contrasting strategies revealed the intelligence of plants in balancing between survival, growth and reproduction, depending on environmental contexts.