Azolla is unique because it is one of the fastest growing plants on the planet – yet it does not need any soil to grow.

Unlike almost all other plants, azolla is able to get its nitrogen fertilizer directly from the atmosphere. That means that it is able to produce biofertilizer, livestock feed, food and biofuel exactly where they are needed and, at the same time, draw down large amounts of CO₂ from the atmosphere, thus helping to reduce the threat of climate change.

How is it able to do this?

Azolla and Anabaena – the Perfect Marriage

Azolla is able to do this because it has a unique mutually beneficial ‘symbiotic relationship‘ with a cyanobacterium (blue-green alga) called  Anabaena.

Each partner gives something to the other in this Perfect Marriage.

The Azolla-Anabaena symbiosis. Each partner gives something to the other.

Azolla provides an enclosed environment for anabaena within its leaves. In return, anabaena sequesters nitrogen directly from the atmosphere which then becomes available for azolla’s growth, freeing it from the soil that is needed by most other land plants for their nitrogen fertilization.

The oldest azolla fossils are more than 70 million years old, representing the remains of plants that lived during the Late Cretaceous Period when dinosaurs roamed the earth.  They occur in sediments that were deposited in quiescent freshwater bodies, such as lakes, ponds and sluggish rivers, identical to those inhabited by modern azolla.

Fossil azolla (left) has leaves (circled above in red) and tendrils (circled in blue) that are identical to those of modern azolla (right). The fossil is from the Green River Formation of Colorado, dated between 50.5 and 55.5 million years. The photograph was kindly provided by Dr Ian Miller of the Denver Museum of Nature and Science.

Several other symbioses are known between plants and cyanobacteria – for example in legumes – but the azolla-anabaena relationship is the only known symbiosis in which a cyanobacterium passes directly to subsequent generations via the plant’s reproductive sporangia and spores.

So azolla and anabaena have never been apart for 70 million years. During that Immense period of time, the two partners have co-evolved numerous complementary ways that make them increasingly efficient.

That is why azolla is able to produce large quantities of biofertilizer, food, livestock feed and biofuel without using land needed to grow food and biofuel, or natural ecosystems such as rainforests.

The challenge

The challenge, then, is to work with azolla and use its remarkable properties to help us weather the Perfect Storm that now threatens us and the other species with whom we share our planet.