Specific activity of phosphorus in mycorrhizal and non-mycorrhizal plants in relation to the availability of phosphorus to plants

• Published in: Soil biology & biochemistry 1984, Vol.16 (4), p.299-304
• Main Authors: Bolan, N.S., Robson, A.D., Barrow, N.J., Aylmore, L.A.G.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Economic plant physiology; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; plant biochemistry; plant physiology; Soil-plant relationships. Soil fertility. Fertilization. Amendments; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...)
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(84)90023-3

Phosphate was allowed to react with a soil to which iron hydroxide had been added. The P was then labelled by a subsequent addition of 32P. Soil P was extracted by 10 m m CaCl 2, 0.5 m NaHCO 3, and acid NH 4F solutions and the specific activity of P in the extracts was measured. Subterranean clover plants were grown both with and without a mycorrhizal fungus. Phosphorus contents and the specific activities of P in the plant shoots were determined. For mycorrhizal plants, adding iron hydroxide had no effect on the amount of P taken up, but for non-mycorrhizal plants it decreased the uptake. However there was no effect of iron hydroxide or of mycorrhizal infection on the specific activity of P in the plants. Adding iron hydroxide had no effect on the amount of P extracted by acid NH 4F, but decreased the P extracted by 10m m CaCl 2 and by 0.5 m NaHCO 3. The specific activity of P in the extracts was not affected by the addition of iron hydroxide and was the same for the three extractants. Further, the specific activity of P in all extractants was similar to that of P in both mycorrhizal and non-mycorrhizal plants. Thus differences in the availability of soil P to mycorrhizal and non-mycorrhizal plants and to the extractants were not reflected by differences in labelling. It therefore follows that lack of difference in specific activity between mycorrhizal and non-mycorrhizal plants does not eliminate the possibility that mycorrhizal plants can obtain P that was unavailable to non-mycorrhizal plants.