Abstract:
Nitrogen fixing legumes rely on phosphorus for nodule formation, nodule function and the energy costs
of fixation. Phosphorus is however very limited in soils, especially in ancient sandstone-derived soils such
as those in the Cape Floristic Region of South Africa. Plants growing in such areas have evolved the ability
to tolerate phosphorus stress by eliciting an array of physiological and biochemical responses. In this
study we investigated the effects of phosphorus limitation on N2 fixation and phosphorus recycling in
the nodules of Virgilia divaricata (Adamson), a legume native to the Cape Floristic Region. In particular, we
focused on nutrient acquisition efficiencies, phosphorus fractions and the exudation and accumulation
of phosphatases. Our finding indicate that during low phosphorus supply, V. divaricata internally recycles
phosphorus and has a lower uptake rate of phosphorus, as well as lower levels adenylates but greater
levels of phosphohydrolase exudation suggesting it engages in recycling internal nodule phosphorus
pools and making use of alternate bypass routes in order to conserve phosphorus.
