Some time ago we got a question about this phenomenon; the Cycas revoluta showed a strange kind of nodules at the bottom of the caudex. The question was of course whether this is normal or harmful to the plant.
Well known bacteria
In fact, this is a cyanobacteria which was used to be called “blue-green algae” and which lives in symbiosis with the Cycas. This means that the bacteria does absolutely no harm and even contributes positively. The cyanobacteria does this by bonding nitrogen, which is used by the Cycas to produce organic compounds. The bacteria gets carbon and a solid shelter in these special roots in return.
This root growth is also controlled by the Cycad itself and will become larger if there is a greater need for nitrogen but will also reduce in times of abundance.
La Palmeraie ©