Explain the importance of the following structures in plants:
$(i)$ Root nodules (Rhizobium association)
$(ii)$ Stipular tendrils

(N/A) $(i)$ In leguminous plants like bean and pea,the roots develop nodules that house $Rhizobium$ bacteria. These bacteria fix atmospheric nitrogen into a usable form for the plant,which is essential for protein synthesis.
$(ii)$ In some plants,the stipules (leaf-like appendages at the base of the leaf) are modified into tendrils to provide support for climbing. This is known as a stipular tendril. In the pea plant ($Pisum$ $sativum$),the stipules are large and leaf-like,assisting in photosynthesis while the tendrils help the weak stem climb.