Overview of Reproduction in Lower and Higher Plants

• Anther is usually dithecous and tetrasporangiate, having two lobes with four pollen sacs in total.
• In the immature anther, hypodermal cells differentiate into archesporial cells, initiating anther development.
• The archesporial cell divides to form sporogenous tissue (gives rise to microspore tetrads) and parietal cells (form anther wall layers).
• The mature anther wall has four layers: epidermis (protective), endothecium (helps in dehiscence), middle layers (degenerate), and tapetum (nutritive layer).

The process in which each microspore mother cell undergoes meiosis to form a tetrad of haploid microspores (pollen grains) is called as microsporogenesis.

• Anatropous ovule is the most common ovule in angiosperms, where the ovule is inverted so that the micropyle lies close to the funiculus.
• The ovule is attached to the placenta by a stalk called funiculus, and the point of attachment is known as hilum.
• The central tissue of the ovule is nucellus, which is usually surrounded by two integuments (outer and inner).
• The ovule has a micropyle at the apex, chalaza at the base, and an embryo sac embedded in the nucellus.

The process of formation of haploid megaspores from a diploid megaspore mother cell (MMC) in the nucellus of ovule is called as megasporogenesis.

The transfer of pollen grains through water as a medium for pollination is called as hydrophily.

Pollination that occurs below the surface of water where pollen grains sink and reach the stigma is called as hypohydrophily.

Pollination in which pollen grains float on the surface of water and reach the stigma is called as epihydrophily.

Pollination carried out with the help of living organisms is called as biotic pollination.

Pollination carried out with the help of insects is called as entomophily.

Pollination carried out with the help of birds is called as ornithophily.

Pollination carried out with the help of bats is called as chiropterophily.

The yellow, sticky substance present on pollen grains that helps in adhesion to insect body is called as pollenkit.

The process of development of zygote into an embryo is called embryogenesis.

• Seed development begins after fertilization; the fertilized ovule develops into a seed, and the integuments form the seed coat (testa and tegmen).
• Seeds may be endospermic (albuminous) with endosperm present (e.g., maize, coconut) or non-endospermic (exalbuminous) where endosperm is absorbed by the embryo (e.g., pea, bean).
• The micropyle persists as a small pore in the seed coat and helps in the entry of water and oxygen during germination.
• Fruit development is triggered by hormones from developing seeds; the ovary transforms into the fruit and the ovary wall becomes the pericarp.
• Seeds and fruits protect the embryo, store or supply food, aid in dispersal, and help in the continuation and distribution of plant species.

A temporary state of metabolic arrest that enables organisms to survive adverse environmental conditions is called as dormancy.

The formation of an embryo-like structure directly from a gametophytic organ or cell without fertilisation is called as apogamy.

The development of a diploid gametophyte from a diploid sporophytic cell without undergoing meiosis is called as apospory (e.g., Orange, Mango).

The development of fruit from the ovary without fertilisation, resulting in a seedless fruit, is called as parthenocarpy.