Abstract
When white lupin (Lupinus albus L.) is subjected to P deficiency lateral root development is altered and densely clustered, tertiary lateral roots (proteoid roots) are initiated. These proteoid roots exude large amounts of citrate, which increases P solubilization. In the current study plants were grown with either 1 mM P (+P-treated) or without P (-P-treated). Shoots or roots of intact plants from both P treatments were labeled independently with 14CO2 to compare the relative contribution of C fixed in each with the C exuded from roots as citrate and other organic acids. About 25-fold more acid-stable 14C, primarily in citrate and malate, was recovered in exudates from the roots of -P-treated plants compared with +P-treated plants. The rate of in vivo C fixation in roots was about 4-fold higher in -P-treated plants than in +P-treated plants. Evidence from labeling intact shoots or roots indicates that synthesis of citrate exuded by -P-treated roots is directly related to nonphotosynthetic C fixation in roots. C fixed in roots of -P-treated plants contributed about 25 and 34% of the C exuded as citrate and malate, respectively. Nonphotosynthetic C fixation in white lupin roots is an integral component in the exudation of large amounts of citrate and malate, thus increasing the P available to the plant.
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Selected References
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- Coker G. T., Schubert K. R. Carbon Dioxide Fixation in Soybean Roots and Nodules: I. CHARACTERIZATION AND COMPARISON WITH N(2) FIXATION AND COMPOSITION OF XYLEM EXUDATE DURING EARLY NODULE DEVELOPMENT. Plant Physiol. 1981 Apr;67(4):691–696. doi: 10.1104/pp.67.4.691. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Johnson J. F., Allan D. L., Vance C. P. Phosphorus Stress-Induced Proteoid Roots Show Altered Metabolism in Lupinus albus. Plant Physiol. 1994 Feb;104(2):657–665. doi: 10.1104/pp.104.2.657. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Lipton D. S., Blanchar R. W., Blevins D. G. Citrate, Malate, and Succinate Concentration in Exudates from P-Sufficient and P-Stressed Medicago sativa L. Seedlings. Plant Physiol. 1987 Oct;85(2):315–317. doi: 10.1104/pp.85.2.315. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rufty T. W., Mackown C. T., Israel D. W. Phosphorus stress effects on assimilation of nitrate. Plant Physiol. 1990 Sep;94(1):328–333. doi: 10.1104/pp.94.1.328. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Vance C. P., Stade S., Maxwell C. A. Alfalfa root nodule carbon dioxide fixation : I. Association with nitrogen fixation and incorporation into amino acids. Plant Physiol. 1983 Jun;72(2):469–473. doi: 10.1104/pp.72.2.469. [DOI] [PMC free article] [PubMed] [Google Scholar]