Phosphorus exudation

F. S. Zhang, J. Ma, and Y. P, Cao, Phosphorus deficiency enhances root exudation of low-molecular weight organic acids and utilization of sparingly soluble inorganic phosphates by radish (Raphanus. sativus L.) and rape Bra.ssica napus L.) plants. 

Phosphorus (P) is one of the major limiting factors for plant growth in many soils. Plant availability of inorganic phosphorus (Pi) can be limited by formation of sparingly soluble Ca phosphates, particularly in alkaline and calcareous soils by adsorption to Fe- and Al-oxide surfaces in acid soils and by formation of Fe/ Al-P complexes with humic acids (94). Phosphorus deficiency can significantly alter the composition of root exudates in a way that is, at least in some plant species, related to an increased ability for mobilization of sparingly soluble P sources (29,31,71). 

Figure 5 Model of phosphorus (P) deficiency-induced physiological changes associated with the release of P-mobilizing root exudates in cluster roots of white lupin. Solid lines indicate stimulation and dotted lines inhibition of biochemical reaction sequences or mclaholic pathways in response to P deliciency. For a detailed description see Sec. 4.1. Abbreviations SS = sucrose synthase FK = fructokinase PGM = phosphoglueomutase PEP = phosphoenol pyruvate PE PC = PEP-carboxylase MDH = malate dehydrogenase ME = malic enzyme CS = citrate synthase PDC = pyruvate decarboxylase ALDH — alcohol dehydrogenase E-4-P = erythrosc-4-phosphate DAMP = dihydraxyaceConephos-phate APase = acid phosphatase.

J. F. Johnson, D. L. Allan, C. P. Vance, and G. Weiblen, Root carbon dioxide fixation by phosphorus deficient Litpinus aihus. Contribution to organic acid exudation by proteoid roots. Plant Physiol. II2 9 (1996). 

M. Li, T. Shinano, and T. Tadano, Distribution of exudates of lupin roots in the rhizosphere under phosphorus deficient conditions. Soil Sci. Plant Nutr. 43 237 (1997). 

S. M. Schwab, J. A. Menge, and R. T. Leonard, Quantitative and qualitative effects of phosphorus on extracts and exudates of sudangrass roots in relation to vesicular-arbuscular mycorrhiza formation. Plant Physiol. 73 761 (1983). 

M. Ratnayake, R. T. Leonard, and A. Menge, Root exudation in relation to supply of phosphorus and its possible relevance to mycorrhizal infection. New Phytol. 81 54.3 (1978). 

J. H. Graham, R. T. Leonard, and J. A. Menge, Membrane mediated decrease in root exudation responsible for phosphorus inhibition of vesicular arbuscular mycor-rhizae formation. Plant Physiol. 6S 548 (1981). 

W. K. Gardner. G. D. Parbery, D. A. Barber, and L. Swinden, The acquisition of phosphorus by Litpimts albus L. V. The diffusion of exudates away from roots a computer simulation. Plant and Soil 72 13 (1983). 

Lu Y, Wassmann R, Neue HU, Huang C. Impact of phosphorus supply on root exudation, aerenchyma formation and methane emission of rice plants. Biogeochemistry. 1999 47 203-218. 

Keywords Climate change Exudation Niche Phosphorus Phytodiversity... 

Miiller R, Morant M, Jarmer H, Nilsson L, Nielsen TH (2007) Genome-wide analysis of the ara-bidopsis leaf transcriptome reveals interaction of phosphate and sugar metabolism. Plant Physiol 143 156-171. doi http //www.plantphysiol.org/cgi/content/abstract/143/l/156 Neumann G, Romheld V (1999) Root exudation of carboxylic acids and protons in phosphorus-deficient plants. Plant Soil 211 121-130... 

Shane MW, de Vos M, de Roock S, Cawthray GR, Lambers H (2003b) Effects of external phosphorus supply on internal phosphorus concentration and the initiation, growth and exudation of cluster roots in Hakea prostrata R.Br. Plant Soil 248 209-219. doi http //dx.doi. org/10.1023/A 1022320416038... 

Newman, E.I., Miller, M.H. Allelopathy among some British grasslands species. II Influence of root exudates on phosphorus uptake. J Ecol 1977 65 399-411. 

Hocking, P. J. (2001). Organic acids exuded from roots in phosphorus uptake and aluminum tolerance of plants in acid soils. Adv. Agron. 74, 63-97. 

Gaume, A., Machler, F., and Frossard, E., Aluminum resistance in two cultivars of Zea mays L. root exudation of organic acids and influence of phosphorus nutrition. Plant Soil, 234, 73-81, 2001. 

Schilling G, Gransee A, Deubel A, Lezovic G and Ruppel S (1998) Phosphorus availability, root exudates, and microbial activity in the rhizosphere. 

Attiwill and Adams, 1993 Seeling and Zasoski, 1993 Oehl et ah, 2004). Phosphorus dynamics in the rhizosphere are further influenced by extracellular root and microbial phosphatase enzymes that hydrolyse organic phosphorus, microbial exudates that solubilize and/or desorb phosphate, and symbiotic mycorrhizal fungi that absorb phosphorus and transport it to plant roots (Smith and Read, 1997 Richardson, 2001). 

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