Growth and resource allocation in response to flooding in the emergent sedge Bolboschoenus medianus

Abstract

The effects of flooding (+20 to -60 cm) on growth and biomass allocation in Bolboschoenus medianus (V. Cook) Sojak are investigated. Relative Growth Rate (RGR) decreased from 43.7 mg g-1 day-1 at 0 cm to 19.5 mg g-1 day-1 at -60 cm. Net Assimilation Rate (NAR) was related to RGR (r2 = 0.97) and fell from 17.5 g m-2 day-1 at 0 cm to 7.5 g m-2 day-1 at - 60 cm. Leaf Area Ratio (LAR) was unrelated to RGR and varied from 2.4-2.7 m2 kg-1. The plants adjusted their canopy height by culm extension, leaf recruitment and more vertically-orientated submersed leaves. As depth increased, the allocation of biomass to culms increased but allocations to tubers, rhizomes and roots decreased. Culm and tuber biomass were inversely related, suggesting that culm extension was supported by translocation from tubers. B. medianus appears to change its morphology: to maintain LAR by allocating below-ground biomass to culms, despite lower RGR.