Cross section of a pea root nodule
Numéro d’image : 13504461
| Scanning electron micrograph of the cut surface of a root nodule of a garden pea, Pisum sativum. The picture shows a cross section of a small nitrogen-fixing nodule, 1mm in diameter. It is bounded by cortical cells (pink) enclosing a mass of spongy cells with cross walls (yellow). Embedded within this tissue are (dark red) cells containing a network of membranes filled with bacteroids of Rhizobium leguminosarum. Air from the surrounding soil reaches these cells via the sponge; the bacteroids, using a haem protein - leghaemoglobin - fix the atmospheric nitrogen to produce ammonium salts. This is an example of mutualism, or symbiosis. The bacterium gains a sequestered environment, and the plant uses the fixed nitrogen for its growth. Globally, nitrogen fixation by micro-organisms produces about three times more fertiliser"" - 150-200m tonnes/yr - than the entire world chemical industry." | |
| Licence : | Droits gérés |
| Crédit: | Science Photo Library / Burgess, Dr. Jeremy |
| Taille de l’image : | 4600 px × 4100 px |
| Model Release : | Non requis |
| Restrictions : | - |
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