Morphology of Flowering Plants — Core Principles

Core Principles

Morphology of flowering plants is the study of their external structure, providing insights into their form, function, and classification. The plant body is organized into a root system (underground) and a shoot system (above ground).

Roots anchor the plant, absorb water and minerals, and can be tap, fibrous, or adventitious, often modified for storage or support. The stem, developing from the plumule, bears leaves, flowers, and fruits, facilitating transport and sometimes modified for storage, propagation, or protection.

Leaves, the primary photosynthetic organs, exhibit diverse shapes, venation patterns (reticulate or parallel), and arrangements (phyllotaxy: alternate, opposite, whorled), and can be simple or compound.

They also undergo modifications like tendrils or spines. Flowers, the reproductive structures, are arranged in inflorescences (racemose or cymose) and consist of sepals, petals, stamens, and carpels. Their symmetry (actinomorphic or zygomorphic), ovary position, aestivation (petal arrangement), and placentation (ovule arrangement) are key diagnostic features.

Fertilized ovaries develop into fruits, which can be true, false, or parthenocarpic, enclosing seeds. Seeds, containing an embryo and stored food, are either albuminous or non-albuminous, representing the plant's dispersal and survival unit.

Understanding these basic structures and their modifications is crucial for identifying and classifying angiosperms.

Important Differences

vs Racemose Inflorescence

Aspect	This Topic	Racemose Inflorescence
Growth of Main Axis	Indefinite, continues to grow.	Definite, terminates in a flower.
Arrangement of Flowers	Acroptetal succession (youngest at apex, oldest at base).	Basipetal succession (oldest at apex, youngest at base).
Opening of Flowers	Flowers open from base to apex.	Flowers open from apex to base.
Number of Flowers	Potentially indefinite number of flowers.	Limited number of flowers.
Examples	Mustard, Radish, Gulmohar.	Jasmine, Solanum, Cotton.

Racemose and cymose inflorescences represent two fundamental patterns of flower arrangement on a plant's floral axis, primarily differing in the growth habit of the main axis and the sequence of flower opening. Racemose inflorescences exhibit indeterminate growth, with the main axis continuously elongating and producing flowers laterally in an acropetal order, meaning younger flowers are at the top. This allows for a prolonged flowering period. Conversely, cymose inflorescences show determinate growth, where the main axis terminates in a flower, thus limiting its growth. Flowers in cymose inflorescences open in a basipetal order, with the oldest flower at the apex. These distinct patterns are crucial for plant identification and understanding reproductive strategies.