Carbon Economy of Sour Orange in Relation to Mycorrhizal Colonization and Phosphorus Status

• Published in: Annals of botany 1993-01, Vol.71 (1), p.1-10
• Main Authors: Eissenstat, D.M., Graham, J.H., Syvertsen, J.P., Drouillard, D.L.
• Format: Article
• Language: English
• Subjects: 14carbon; Agronomy. Soil science and plant productions; Biological and medical sciences; Carbon; carbon economy; Citrus aurantium; Citrus aurantium L; Citrus aurantium L., sour orange, carbon economy, 14carbon, CO2 assimilation, vesicular-arbuscular mycorrhizae, phosphorus fertilization, phosphorus nutrition; CO2 assimilation; Fibrous roots; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Glomus intraradices; Mycorrhizae; net assimilation rate; Nitrogen, phosphorus, potassium fertilizations; nutrient requirements; nutrient transport; Nutrition; Phosphorus; Phosphorus fertilization; phosphorus nutrition; photosynthesis; Plant growth; plant nutrition; Plant roots; Plants; Radiocarbon; Seedlings; Soil-plant relationships. Soil fertility. Fertilization. Amendments; sour orange; vesicular arbuscular mycorrhizae
• ISSN: 0305-7364; 1095-8290
• DOI: 10.1006/anbo.1993.1001

The effects of plant phosphorus (P) status and the mycorrhizal (M) fungus, Glomus intraradices Schenck & Smith, on the carbon (C) economy of sour orange (Citrus aurantium L.) were determined during and following active M colonization. There were four treatments: M seedlings grown at standard-strength (1 mM) P (M1) and nonmycorrhizal (NM) plants grown at one, two and five times standard-strength P (NM1, NM2 and NM5). Mycorrhizal colonization, tissue dry mass, P content, root length and leaf area were determined in five harvests from 6 to 15 weeks of age. Rate of C assimilation (A) was determined at 7, 8 and 12 weeks by gas exchange. Partitioning of 14 C was determined from 7 to 15 weeks using a 10-min pulse followed by a 24-h chase period. For a given attribute, M1 plants were compared to the curve defining the NM response as a function of tissue P concentration. In contrast to the large effects of P nutrition on C economy of sour orange, M effects were generally subtle. Mycorrhizae increased the root biomass fraction, the root length/leaf area ratio and the percentage of 14C recovered from below-ground components. A higher percentage of below-ground 14 C was in the respiration and soil fractions in M than NM plants of equivalent P status. Mycorrhizal plants tended to enhance A only for a brief period. Mycorrhizal plants had lower relative growth rates than NM plants of equivalent P status, suggesting that the temporarily enhance A of M plants did not fully compensate for their greater below-ground carbon expenditure. Problems of interpreting the dynamic effects of mycorrhizae on C economy that are independent of P nutrition are discussed.