Biology · Oct / Nov 2025 · Paper 22 · Question 3

Azolla is a genus of small ferns that float in slow-flowing or stationary fresh water. Azolla has cavities in its leaves that contain nitrogen-fixing bacteria called Anabaena azollae. In some parts of the world, farmers grow Azolla in their rice fields. Rice fields are flooded with water so that rice plants grow half submerged. Fig. 3.1 shows rice and Azolla growing together in a flooded field. Fig. 3.2 shows a section through an Azolla leaf. 0.2 mm rice plants clumps of Azolla nitrogen-fixing bacteria leaf cavity containing air Fig. 3.1 Fig. 3.2

Read automatically from the paper; the printed page above is exact.