Botany · Ch 9 — Plant Breeding
Azolla
Azolla
Azolla is a small, free-floating water fern that lives in symbiosis with the nitrogen-fixing blue-green alga Anabaena azollae, housed within cavities on its fronds. Together they fix atmospheric nitrogen and make it available to the surrounding soil and water (Figure 9.5). Azolla is widely used as a biofertilizer for wetland (lowland) rice cultivation, where it can contribute an estimated 40–60 kg of nitrogen per hectare per crop. Because Azolla decomposes quickly once incorporated into the soil, releasing its fixed nitrogen rapidly, it has considerable agronomic value for boosting …
What this figure shows. Two-part figure: (a) a photograph of a flooded rice paddy field with its water surface covered by a dense green mat of the small free-floating fern Azolla, showing how it is grown directly in the crop field; (b) a close-up photograph of individual Azolla plants showing their tiny, overlapping, scale-like leaves and branching fronds, within which the symbiotic nitrogen-fixing cyanobacterium Anabaena azollae lives in sp …