(i) Underground parts of a plant are not always roots. Sometimes stem or stem branches occur underground to perform some special functions. For example, potato tuber is a modified stem which is underground. A potato tuber shows nodes and internodes, scale leaves and buds at the nodes. It also has an apical bud at the tip of potato tuber which confirms it as a stem.
(ii) Flower is a modified shoot consisting of a highly reduced stem branch to form thalamus in which the nodes are borne only towards the tip. The floral parts, i.e., sepals, petals, stamens and carpels are arranged in their respective whorls and arise from nodes The growing point of floral bud is used up in the production of floral organs.