Revision: Reproduction >> Sexual Reproduction in Flowering Plants CUET (UG) Sexual Reproduction in Flowering Plants

When calyx and corolla are not differentiated, the floral envelope is called the perianth.

Individual members of the perianth are called tepals.

The pattern of ovule arrangement in the ovary is called placentation. 

A modified, compressed reproductive shoot of angiosperms bearing sepals, petals, stamens, and carpels, meant for sexual reproduction, is called a flower.

A circular arrangement of floral organs at the same level on the thalamus is called a whorl.

The swollen terminal part of the pedicel on which all floral whorls are arranged is called the thalamus or receptacle.

A flower that has both androecium (male part) and gynoecium (female part) in the same flower is called a bisexual flower.
Example: Hibiscus

A specialised axis or branch over which flowers are produced or borne in definite manner is known as inflorescence.

A flower that has only one reproductive whorl (either androecium or gynoecium) is called a unisexual flower.

• If it has only androecium: male flower
• If it has only gynoecium: female flower
  Example: Papaya

A flower that has a stalk called pedicel for support is called a pedicellate flower.

The structure in flowering plants that develops into a seed after fertilization is called the ovule.

The controlled crossing of selected male and female parent plants to produce genetically superior offspring is called artificial hybridization.

When pollination occurs within the same flower or between two flowers on the same plant, it is called self-pollination.

or

Transfer of pollen grains from the anther to the stigma of the same flower or another flower on the same plant is said to be self~pollination.

Transfer of pollen grains from the anther to stigma is called pollination.

When pollination occurs between flowers on two different plants of the same species, it is called cross-pollination.

or

Transfer of pollen grains from the anther of a flower from one plant to the stigma of the flower on another plant is called cross-pollination

Union of the second male gamete with two polar nuclei to form endosperm, along with fertilization, is called double fertilization.

• Flower: A modified shoot and the reproductive unit of angiosperms.
• Structure: Consists of four whorls—calyx, corolla (accessory), androecium, and gynoecium (reproductive).
• Types by sex: Flowers may be unisexual (male/female) or bisexual (both present).
• Symmetry: Actinomorphic (radial), zygomorphic (bilateral), or asymmetric.
• Based on floral parts: Flowers can be trimerous, tetramerous, or pentamerous depending on the number of parts.
• Position of ovary: Hypogynous (superior), perigynous (half inferior), epigynous (inferior).

• Sexual reproduction involves the fusion of male and female gametes from two parents to form a diploid zygote.
• A flower is the reproductive structure in plants that produces gametes and enables fertilisation.
• A flower has four whorls: calyx, corolla, androecium (male), and gynoecium (female).
• It includes meiosis for gamete formation and fertilisation, producing genetically different offspring.
• Sexual reproduction occurs in three stages: pre-fertilisation, fertilisation, and post-fertilisation.

• A typical anther is dithecous and tetrasporangiate, having two lobes, each with two microsporangia (pollen sacs).
• Microsporangia contain sporogenous tissue, which develops into microspore mother cells that form pollen grains.
• The anther wall has four layers: epidermis, endothecium, middle layers, and tapetum.
• The tapetum provides nutrition to developing pollen, and microspore mother cells undergo meiosis to form haploid microspores.
• During anther dehiscence, the endothecium helps in rupture at the stomium, releasing pollen grains for pollination.

• The ovule is an integumented megasporangium present inside the ovary and is attached to the placenta by a stalk called the funicle.
• The nucellus is the central part containing reserve food, surrounded by one or two integuments for protection.
• The integuments leave a small opening called the micropyle at the apex, while the basal region is called the chalaza, and the attachment point is the hilum.
• The ovule is commonly anatropous, and contains an embryo sac (female gametophyte) with structures like egg cell, synergids, and polar nuclei.
• During development, the ovule arises from the placenta, and integuments grow around the nucellus to form a mature ovule.

• Artificial hybridisation is used in crop improvement to combine desirable traits of different plants.
• It ensures that only selected (desired) pollen is used for pollination.
• Emasculation → removal of anthers from bisexual flowers before they release pollen.
• Bagging → covering the flower to prevent unwanted pollen contamination.
• When stigma becomes receptive, desired pollen is applied, and the flower is rebagged for fruit development.