Rapid change in relative growth rate between the vegetative and reproductive stage of the life cycle in Plantago coronopus

Abstract

A growth experiment with seedlings from Plantago coronopus, originating from small (0.13 mg) and large (0.20 mg) seeds, was conducted under optimum nutrient conditions to gain insight into the physiological processes associated with the vegetative and generative phase of plant growth. The relative growth rate (RGR) during the vegetative stage was 300 mg g-1 d-1 and dropped at the initiation of flowering buds to 60 mg g-1 d -1, a fivefold reduction, while remaining exponential. Investment in reproductive structures had prevalence over vegetative structures during the generative phase of the life cycle. The RGR of reproductive structures was 105 mg g-1 d-1. The initiation of flowering was stage-dependent. After the formation of about 14 leaves, plants started to form flowering buds, independent of weight or leaf size. The shoot:root ratio stayed the same during both the vegetative and generative stages. The change from a two-compartment system (shoot and root) to a three-compartment system (shoot, root and reproductive structures) did not change the balance or functional equilibrium between root and shoot. Seed size effects lasted until the end of the experiment and were reflected in all morphological measurements. © New Phytologist (2004).