Q.Students were on the excursion to a botanical garden. They noted following observation. Will you be able to help them in understanding those conditions? While having lunch, onion slices were served to them. Teacher asked which part of the plant are you eating?

The stem develops underground, sub-aerial and aerial modifications for storage, perennation, propagation and photosynthesis, all recognisable by the presence of nodes/internodes and buds (unlike modified roots). Underground stems: the stem tuber (Potato) swells at its tip and bears axillary-bud 'eyes' at nodal scale leaves; the rhizome (Ginger, Turmeric) is a horizontal/oblique stem with nodes, scale leaves and buds, spreading by sympodial growth via lateral buds or monopodial growth via the terminal bud (Nymphaea, Lotus, fern); the bulb is a reduced discoid stem wrapped in concentric fleshy storage leaves, either tunicated/layered (Onion) or scaly/compound tunicated (Garlic); the corm (Colocasia, Amorphophallus) is a swollen vertical stem-internode with ring-like nodes and adventitious buds/roots. Sub-aerial stems: the trailer spreads flat over the ground (Euphorbia); the runner sends out horizontal green branches from a crown (Cynodon); the stolon arches over and roots where it touches ground (Mentha); the sucker grows underground before emerging as a new shoot (Chrysanthemum, Banana); the offset is a one-internode rosette runner (Pistia, Eichhornia). Aerial modifications: the thorn is a hard modified bud (apical in Car …