Different Parts of a Dicot Seed Embryo: Structure, Differences, Examples

Definition Of A Dicot Seed

A seed that contains two cotyledons storing food for the developing plant embryo. Examples are beans, peas, and sunflowers. Knowing about seed embryos can provide better insight into plant development by looking through the studies on the very early stages of plant growth and differentiation. This information is useful in agriculture and botany to enhance yield, develop new strains of plants, and fathom basic plant biology.

Structure Of A Dicot Seed

The structure of a dicot seed include:

Seed Coat

The seed coat is that hard outer covering of the seed that protects the inner organs from mechanical injury, pests, and diseases. It consists of two layers, i.e., the outer layer, testa and the inner one, tegmen. The testa is the rigid, outermost protective cover while the tegmen is the thinner, inner delicate membranous layer providing extra protection.

Hilum And Micropyle

The hilum is a scar on a seed coat, that marks a point where a seed was attached to the ovary wall. Typically it is a minor, dark dot. Directly adjacent to a hilum is a small pore called a micropyle. It allows water to pave the way for seed and initiate germination. Meanwhile, it allows for gas exchange to take place

Parts Of A Dicot Seed Embryo

The parts of a dicot seed embryo include:

Embryonic Axis

The embryo has three central parts to its axis body, the radicle, hypocotyl, and epicotyl. The axis is essential in that the plant's primary root and shoot systems arise from it.

Radicle

The radicle is the embryonic root that becomes the first to extend into the soil during germination, thus anchoring the seedling and absorbing necessary water and nutrients for further growth.

Hypocotyl

The embryonic axis developed between the radicle and the cotyledons is stem-like. It also elongates during germination, lifting the cotyledons above the ground, and thus forms the lower stem of the seedling.

Epicotyl

The epicotyl is that part of the embryonic axis above the cotyledons. It will become the upper stem and leaves of the seedling and be part of the shoot system of the plant.

Cotyledons

Cotyledons are leaves of the embryo and are, hence, called the seed leaves. Dicotyledons have two cotyledons, and they are storage organs that supply nutrients to the seedling in its early stages of growth until it has true leaves which can photosynthesise.

Seed Germination Process

The seed germination process is explained below:

Stages Of Germination

Germination starts with imbibition, which is the uptake of water by the seed, causing it to swell. This triggers enzymes that digest stored foods to provide energy for growth. The radicle emerges and forms the primary root. The hypocotyl emerges next. It elongates behind the cotyledons, pushing them above ground. Finally, the epicotyl grows forming the shoot and true leaves.

Environmental Conditions Required

Seeds require maximum temperature, moisture, and oxygen conditions. Temperature affects the enzymes' activity and metabolic rate. Moisture is required for the metabolic processes to be initiated while oxygen is required for cellular respiration to enable the energy used in growth to be gained.

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