Phosphorus absorption, translocation, and secretion in <i>Nuphar luteum</i>1

Abstract

Absorption, translocation, and subsequent secretion of phosphorus by Nuphar luteum was studied under laboratory and field conditions. Laboratory studies showed that absorption rates (per gram dry weight of absorbing organ) differed with the absorbing organ (roots &gt; submersed leaves &gt; floating leaves). Uptake rates for submersed leaves gave a hyperbolic curve, saturating at high P concentrations. In the Chowan River, North Carolina, native plants were enclosed in chambers for 24 h while simultaneously exposing submersed leaves to ‘Y and roots of the same plant to 32 P. Translocation was bidirectional, with the acropetal pathway (roots to leaves) dominating. Translocation rates were affected more by seasons (summer &gt; spring &gt; winter) than were absorption rates by roots. Seasonal differences in translocation rates were significant ( P &lt; 0.05), but absorption rates for roots were not. About four times more P moved acropetally than basipetally during summer. Translocated P was secreted by roots and submersed leaves during summer only.