The Hard Life of Prokaryotes in the Leaf Cavities of Azolla

Abstract

Life of cyanobionts and bacteriobionts inside the leaf cavities of Azolla cannot be so easy. Fern shows many features of remedation plant, able to adapt itself to the change of the environmental conditions such as high light intensity, high temperature or water composition. Cyanobionts seem to modify their metabolism according to that of the fern, and whenever the host life conditions become stressing, the symbiont can be eliminated (Hill, 1975; Kitoh et al., 1991). Therefore speaking in term of symbiosis, it may be not so easy for the symbionts, since Azolla behaves at its convenience, forcing them to follow its benefit. Anyway, some authors consider the Azolla-Anabaena relationship like an happy marriage between lucky partners, where each of them contributes to the menage. Some considerations can be made on the different aspects of such unusual association.