$(i)$ In leguminous plants of bean, pea, underground adventitious root has many small and big nodes. These nodes are Rhizom. Rhizobium bacteria lives on it and develops that fixes nitrogen and provides nitrogen to plants.

$(ii)$ The stem is weak in pea plant. In that leaflets of compound leaf get converted into stem tendril and help in climbing. So stipules are big in pea, help in photosynthesis being leaf like stem. It is called stipular tendril.