How the form of roots, stems, leaves and flowers suits their roles
Morphology is the study of the external form of organisms. Roots may be tap roots, as in mustard, or fibrous roots, as in wheat, and some are modified for storage (carrot), support (prop roots of banyan) or breathing (pneumatophores in mangroves). Stems bear nodes and internodes and can be modified as tendrils, thorns, underground tubers like potato and rhizomes like ginger. Leaves show different venation, reticulate in dicots and parallel in monocots, and phyllotaxy, the arrangement of leaves on the stem, which may be alternate, opposite or whorled.
A flower is a modified shoot for reproduction, with calyx, corolla, androecium and gynoecium. Flowers may be actinomorphic or zygomorphic, and the ovary may be superior or inferior. Placentation describes how ovules attach inside the ovary, such as marginal in pea. After fertilisation, the ovary becomes a fruit and the ovules become seeds, which may be dicot with two cotyledons or monocot with one. Families are described with floral formulae; for example, Fabaceae (pea family) has papilionaceous flowers, Solanaceae includes tomato and potato, and Liliaceae includes onion.
Why it matters
Plant morphology helps farmers, botanists and gardeners identify plants, choose crops and recognise weeds. Knowing modified roots and stems explains why we eat potatoes, ginger and carrots as different plant parts. Floral structure is key to plant breeding and pollination, and it is the basis for classifying flowering plants into families.
Key terms
- Phyllotaxy
- The pattern in which leaves are arranged on a stem.
- Venation
- The arrangement of veins in a leaf blade.
- Placentation
- The arrangement of ovules within the ovary of a flower.
- Floral formula
- A shorthand that summarises the number and arrangement of flower parts.