Plant Reproduction and Germination

If we keep a leaf of bryophyllum on damp soil, within a day or two,  buds appear from the margin of leaf.

The lower swollen portion of archegonia is known as venter.

Seed coat dormancy is observed when the seed coat is impermeable to water, and gases (oxygen). It requires action by weathering, microorganisms, passage through an animal's digestive track, or fire to soften the seed coat.

Dormancy that is caused by an impermeable seed coat is known as physical dormancy. Physical dormancy is the result of impermeable layer(s) that develops during maturation and drying of the seed or fruit. This impermeable layer prevents the seed from taking up water or gases. As a result, the seed is prevented from germinating until dormancy is broken.

Perisperm is the residual, persistent nucellus found inside some seeds.

In a monocarpellary (one carpel), unilocular (one chamber) ovary, ovules are arranged along the ventral suture where the carpel margins fuse. This marginal placentation is characteristic of legumes. Axile is for multicarpellary ovaries, parietal for syncarpous ovaries with false septa, basal for single basal ovule.

Marginal placentation (a) develops from bicarpellary, syncarpous ovary that becomes unilocular (as in Fabaceae). Parietal placentation (c) develops from multicarpellary, syncarpous, unilocular ovary where ovules attach to the ovary wall. Basal placentation (d) develops from bicarpellary, syncarpous, unilocular ovary with single ovule at base. Axile placentation (b) requires multilocular ovary, not unilocular.

Axile placentation occurs when ovules are attached to a central column formed by the fused margins of carpels. In a pentacarpellary (5 carpels), syncarpous (fused carpels), and pentalocular (5 chambers) ovary, this central arrangement is exactly what creates the axile pattern. Parietal placentation would give a unilocular ovary, while marginal occurs only in monocarpellary conditions.

Parietal placentation characteristically occurs in multicarpellary, syncarpous ovaries where the ovules are borne on the inner walls (periphery) of a single chamber (unilocular). The fusion of carpels creates one large cavity with ovules attached to the walls, unlike axile placentation which has multiple chambers.

In paddy (Oryza sativa, rice), the grain (caryopsis) remains enclosed by persistent bracts (lemma and palea) collectively called the chaff. This is characteristic of the grass family (Poaceae).

Germination is the process by which a seed begins to grow and develop into a new plant. Radicle is the embryonic root, Plumule is the embryonic shoot, Annual refers to a plant life cycle.

Some plants never open to ensure complete self-pollination. This condition is called cleistogamy, e.g., Commelina bengalensis, Oxalis, Viola, etc.. The cleistogamous flowers are bisexual small, inconspicuous, colourless and do not secrete nectar.

Ovule as well as embryo sac is curved like a horse shoe e.g., Lemna, Poppy, Alisma.

A sprout is a very young plant (newly germinated) or the new growth on a plant (a shoot).

Chalazogamy is a process of fecundation in which the pollen tube penetrates into the embryo sac through the tissue of the chalaza.