Journal
JOURNAL OF PLANT PHYSIOLOGY
Volume 174, Issue -, Pages 16-25Publisher
ELSEVIER GMBH
DOI: 10.1016/j.jplph.2014.10.005
Keywords
N x P interaction; N-2 fixation; P-acquisition; P-limitation; Phosphoenolpyruvate carboxylase
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Funding
- National Research Foundation (NFR)
- UCT
- Oppenheimer Memorial Trust
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Podalyria calyptrata is from fynbos soils with low availability of phosphorus (P) and nitrogen (N). We investigated the physiological basis for tolerance of low P supply in nodulated P. calyptrata and examined responses to increased supply of combined-N as Ca(NO3)(2) and P. It was hypothesized that increasing supply of combined-N would stimulate P-acquisition mechanisms and enhance plant growth with high P supply. Biomass, leaf [N] and [P], organic acid and phosphatase root exudates, and phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase (MDH) activity in nodules and roots were examined in two N x P experiments. Low P supply decreased leaf [P] and limited growth, decreasing the nodule: root ratio but increasing nodular PEPC and MDH activity for enhanced P-acquisition or P-utilization. At low P supply, a N-induced demand for P increased root exudation of citrate and PEPC and MDH activity in roots. Greater combined-N supply inhibited nodulation more at low P supply than at high P supply. With a P-induced demand for N the plants nodulated prolifically and increased combined-N supply did not enhance plant growth. The physiological basis for N-2-fixing P. calyptrata tolerating growth at low P supply and responding to greater P supply is through balanced acquisition of P and N for plant demand. (C) 2014 Elsevier GmbH. All rights reserved.
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