Water depth changes and biomass allocation in two contrasting macrophytes

Abstract

The response of B. arthrophylla and T. procerum in pot experiments to depth and depth changes provided insight into how plants survive fluctuating water levels. At 0 cm depth, most biomass was placed below ground, which can be interpreted as the placement of resource-acquiring tissues (roots, rhizomes) in resource (nutrients, space) -supplying environments. At 50 and 100 cm, the placement of biomass into shoots recognized the need for a higher supply of above-ground resources (light, inorganic carbon, oxygen). However, the responses of the two species to flooding or exposure differed. Rhizome storage supported an increase in the number and height of B. arthrophylla stems when flooded by 50 cm but this species was unable to counteract submergence to 100 cm without the critical loss of root mass. The slow turnover rate of the cuticularized B. arthrophylla stems indicates that biomass needs to be allocated above water as well as above ground. Other responses indicated that this species may be better suited to seasonally fluctuating rather than permanent water levels. T. procerum dealt with water level changes via morphological plasticity. Along with the rapid growth and turnover of the spongy leaves, its shoot and total mass were maintained primarily from resources in the tubers.