THE ROLE OF ANABAENA IN THE AZOLLA-ANABAENA SYMBIOSIS

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SUMMARY

The Anabaena cells in Azolla undergo a developmental pattern of differentiation parallel to that of the fern. At the apex, the algal cells are small and rapidly dividing, and do not fix atmospheric nitrogen. After the leaf cavities are colonized, the algal cells form heterocysts, fix nitrogen and the vegetative cells enlarge considerably. The synchrony between the two partners appears to break down under certain environmental conditions leading to alga-free fern fronds.

Ancillary