147928PD: Coralloid roots of Macrozamia riedlei, or zamia palm, 1965-1984.

Summary

Book caption: Symbiosis is a gentler form of robbery than parasitism, and some groups of plants have developed symbiotic relationships with fungi or bacteria which are harboured in the roots, often in special tissues. The symbionts are able to fix atmospheric nitrogen which becomes available to the host plant, while the symbiont receives water and other nutrients in return. Fig 2.26 shows bacterial nodules on the roots of a native legume, Viminaria juncea. Such nodules are normally produced on the roots of leguminous plants in the families Mimosaceae and Papilionaceae, and have been recorded in at least 300 Australian native species. Fig 2.27 shows so-called coralloid roots of the zamia palm Macrozamia riedlei which harbour a blue-green alga in this case and also have a nitrogen-fixing role. Nodulation similar to that of legumes but involving an actinomycete fungus occurs in species of Casuarina.