Growth and nutrient responses of Eloecharis cellulosa (Cyperaceae) to phosphate level and redox intensity.

Phosphorus (P) availability limits plant growth in many ecosystems. The ability of plants to explore for soil P is often impaired by nonresource stressors. Understanding the effects of these stressors on P acquisition in oligotrophic environments is critical in predicting species dominance. Growth and nutrient responses of Eleocharis cellulosa to redox intensity and phosphate level were evaluated under three redox potentials (Eh) and three phosphate (PO(4)) levels (P). Although low Eh (-150 mV) decreased root length at low P, Eh did not affect shoot height, relative growth rate (RGR), shoot elongation, photosynthesis, or biomass of E. cellulosa. Low PO(4) (10 μg P · L(-1)) strongly inhibited growth. Shoot height, RGR, elongation, photosynthesis, and biomass were lower at 10 μg P · L(-1) than at 80 or 500 μg P · L(-1). None of the growth variables, except the ratio of root-supported biomass to root biomass, significantly differed between the 80 and 500 μg P · L(-1) treatments. At low P, plants allocated relatively more biomass to roots than to shoots, compared to the medium and high P levels. Eleocharis cellulosa is well adapted to flooded conditions that lower soil Eh, and elevated PO(4) levels further promote its growth potential.