Evolution, Biology, Ecology and Uses of Azolla

Dear Colleagues,

Azolla is a small, free-floating freshwater fern that is distinguished from other plants by its permanent symbiosis with the nitrogen-fixing cyanobacterium Nostoc azollae (also known as Anabaena azollae). This unique symbiosis originated in the Late Cretaceous (Campanian) of North America, when whole-genome duplication (WGD) of Azolla's ancestor enabled transmission of the cyanobacteria via the plant’s megaspores. Over the following 80 million years, the two symbionts underwent additional genetic alterations that changed the cyanobacteria from free-living organisms into obligate endosymbionts, with other modifications increasing their nitrogen fixation and Azolla's rapid growth. This resulted in the 'Arctic Azolla Event' when Azolla repeatedly spread across the Arctic Ocean surface 49 million years ago, sequestering large amounts of atmospheric carbon dioxide and initiating the transition from a greenhouse to icehouse climate.

Azolla has been cultivated for hundreds of years in India and East Asia as a renewable low-cost biofertilizer and feed for farmed animals, birds and fish. It is also increasingly studied for its biofuel, biochar and food production, removal of excess nitrogen and phosphorus from water and soil, suppression of harmful cyanobacterial (blue-green algal) blooms, and carbon capture and storage (CCS). These applications are urgently needed with today's climate change and growing human population, making this Special Issue on the Evolution, Biology, Ecology and Uses of Azolla significant and timely.

This Special Issue of Plants invites original research and review articles addressing all aspects of Azolla, including its evolution, genetics, biology, ecology, phytoremediation, agricultural applications, and food security.

Dr. Jonathan Bujak
Dr. Ana Luisa Pereira
Prof. Dr. Henk Brinkhuis
Guest Editors

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