Fruit and Seed — Definition

Definition

In the fascinating world of flowering plants, or angiosperms, the journey from a flower to a new plant involves two incredibly important structures: the fruit and the seed. Think of a flower as the plant's reproductive organ. After successful pollination and fertilization, where pollen grains meet the ovules inside the ovary, a remarkable transformation begins.

The fruit is essentially the mature and ripened ovary of a flower. Its primary job is to protect the developing seeds inside and aid in their dispersal once they are ready. Not all fruits are juicy and sweet like an apple or a mango; many are dry, like the pods of peas or the grains of wheat.

The wall of the ovary develops into the fruit wall, which is called the *pericarp*. This pericarp can be differentiated into three distinct layers: the outermost *epicarp* (skin), the middle *mesocarp* (fleshy part in many fruits), and the innermost *endocarp* (which can be stony, fibrous, or papery, enclosing the seed).

Fruits can be broadly classified based on their origin. A 'true fruit' develops exclusively from the ovary, like a mango. However, sometimes other floral parts, such as the thalamus, also contribute to fruit formation; these are called 'false fruits,' with an apple being a classic example.

Fruits also vary in how many ovaries or flowers they originate from: 'simple fruits' develop from a single ovary of a single flower (e.g., pea, mango), 'aggregate fruits' from multiple separate ovaries of a single flower (e.

g., custard apple), and 'multiple fruits' from the ovaries of an entire inflorescence (e.g., pineapple, jackfruit).

The seed is the ultimate product of sexual reproduction in flowering plants. It develops from the fertilized ovule. Each seed is like a tiny, self-contained package designed to grow into a new plant under favorable conditions.

Inside a seed, you'll find three main parts: a protective outer covering called the *seed coat*, a miniature plant called the *embryo*, and often a food supply. This food supply can be in the form of *endosperm* (a nutritive tissue formed during fertilization) or stored within specialized leaves of the embryo called *cotyledons*.

Seeds that retain endosperm are called *albuminous* (e.g., castor), while those that consume it during development and store food in cotyledons are *exalbuminous* (e.g., pea, bean).

Seeds are also categorized based on the number of cotyledons they possess: *monocotyledonous* seeds have one cotyledon (e.g., maize, wheat), while *dicotyledonous* seeds have two (e.g., pea, gram). The embryo within the seed consists of an *embryonal axis* (which develops into the shoot and root) and the cotyledons.

The part of the embryonal axis above the cotyledons is the *epicotyl*, terminating in the *plumule* (future shoot), and the part below is the *hypocotyl*, terminating in the *radicle* (future root).

Both fruits and seeds are vital for plant survival and human civilization. Fruits provide nutrition and aid in seed dispersal, while seeds are the primary means of propagation for most crops, ensuring food security and biodiversity. Understanding their structure and development is fundamental to comprehending plant biology.