Describe various stem modifications associated with food storage,climbing,and protection.

(N/A) The stem performs several specialized functions in addition to its primary roles of support and conduction. It undergoes modifications to adapt to these functions:
$(A)$ Modification of stems for food storage:
$(i)$ Rhizome: Underground stems like ginger,turmeric,and Colocasia store food and become fleshy. They possess nodes,internodes,scaly leaves,and adventitious roots.
$(ii)$ Tuber: In potato,the tips of underground branches swell due to food storage,forming a round or oval structure called a tuber. The surface has depressions called 'eyes',which contain buds that perform vegetative propagation.
$(iii)$ Corm: Amorphophallus is a condensed,vertical form of a rhizome.
$(B)$ Modifications of stem for climbing:
Stem tendrils: In plants like cucumber,pumpkin,watermelon,and grapevines,axillary buds develop into slender,spirally coiled structures called stem tendrils,which help the plant climb.
$(C)$ Modifications of stem for protection:
Thorns: In plants like Citrus and Bougainvillea,axillary buds are modified into woody,straight,and pointed structures called thorns,which protect the plants from browsing animals.