Journal Article

Low Phosphorus Tolerance Mechanisms: Phosphorus Recycling and Photosynthate Partitioning in the Tropical Forage Grass, <i>Brachiaria</i> Hybrid Cultivar Mulato Compared with Rice

Masahito Nanamori, Takuro Shinano, Jun Wasaki, Takuya Yamamura, Idupulapati M. Rao and Mitsuru Osaki

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 4, pages 460-469
Published in print April 2004 | ISSN: 0032-0781
Published online April 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch056
Low Phosphorus Tolerance Mechanisms: Phosphorus Recycling and Photosynthate Partitioning in the Tropical Forage Grass, Brachiaria Hybrid Cultivar Mulato Compared with Rice

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The Brachiaria hybrid cv. Mulato is well adapted to low-fertility acid soils deficient in phosphorus (P). To study the grassy forage’s mechanisms for tolerating low P supply, we compared it with rice (Oryza sativa L. cv. Kitaake). We tested by using nutrient solution cultures, and quantified the effects of P deficiency on the enzymatic activities of phosphohydrolases and on carbon metabolism in P-deficient leaves. While P deficiency markedly induced activity of phosphohydrolases in both crops, the ratio of inorganic phosphorus to total P in leaves was greater in Brachiaria hybrid. Phosphorus deficiency in leaves also markedly influenced the partitioning of carbon in both crops. In the Brachiaria hybrid, compared with rice, the smaller proportion of 14C partitioned into sugars and the larger proportion into amino acids and organic acids in leaves coincided with decreased levels of sucrose and starch. Hence, in P-deficient leaves of the Brachiaria hybrid, triose-P was metabolized into amino acids or organic acids. Results thus indicate that the Brachiaria hybrid, compared with rice, tolerates low P supply to leaves by enhancing sugar catabolism and by inducing the activity of several phosphohydrolases. This apparently causes rapid P turnover and enables the Brachiaria hybrid to use P more efficiently.

Keywords: Keywords: Brachiaria hybrid — Low P tolerance — Phosphohydrolase — Photosynthate distribution — Rice (Oryza sativa L.).; Abbreviations: APase, acid phosphatase; P, phosphorus; PEPC, phosphoenolpyruvate carboxylase; PEPP, phosphoenolpyruvate phosphatase; Pi, inorganic phosphate; PK, pyruvate kinase; PPT, phosphoenolpyruvate transporter; RNase, ribonuclease.

Journal Article.  7304 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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