Explain how stem is modified variously to perform different functions?

A Under ground stem modifications :
i) Rhizome : It is an underground stem that grows horizontally in a particular depth of the soil.
Eg : Ginger, Turmeric
ii) Corm : It is an underground stem that grows vertically in a particular depth of the soil.
Eg : Colocasia, Amorphophallus (zaminkand)
iii) Stem tuber : Tip of underground branches store food material and become tuberous. Eyes show vegetative reproduction.
Eg : Potato.
iv) Bulb : Stem is reduced and leaf bases store food material.
Eg : Onion.
B. Aerial stem modifications :
i) Stem tendrils : In weak stemmed plants, axillary (or) terminal bud is modified in to slender wiry, spirally coiled structures which helps in climbing purpose, called as stem tendrils.
Eg : (a) From axillary bud: Cucumber, pumpkin, watermelon
(b) From terminal bud: Grapevine
ii) Thorns : These are hard woody, straight and pointed structures protect from grazing animals.
Eg : Bougainvillea, Citrus.
iii) Phylloclade : In xerophytes stem is modified into green colored structures for photosynthesis.
Eg: Opuntia, Casuarina.
C. Sub aerial stem modifications :
i) Runners : Some plants spread to new niches with adventitious roots at nodes.
Eg: Grasses, Strawberry, Oxalis
ii) Stolons : It is a slender, aerial lateral branches arising from the base of the main axis and grows obliquely down wards to touch the ground and produce adventitious roots.
Eg: Nerium, Jasmine
iii) Sucker : Underground branch grows horizontally beneath the soil and come out obliquely upward called sucker.
Eg: Chrysanthemum.