A flower contains the subsequent parts-
Calyx: outermost whorl of a flower. It contains units known as sepals, within the bud stage, petall encloses the remainder of the flower. They typically exhibit inexperienced colouration, at other instances, they are colored like florals. This state of petal is termed as floral leaf.
Corolla: It consists of many numbers of petals and it is the second whorl of the flower. These petals are generally musky. they’re colored, skinny and soft, which will facilitate the method of fertilisation as they’d attract animals and insects.
Reproductive Structure of a Flower
Androecium
It is the male fruitful a part of a flower, comprising stamens and it is the third whorl. Every reproductive structure contains 2 components, namely, reproductive structure and filament. The tip of the reproductive structure is supported by the filament. Here pollens are made by meiosis and disappear eventually.
Anther: this can be a four-lobed sac-like structure answerable for spore formation.
Filaments: These thread-like structures are hooked up to the reproductive structure, and that they keep the reproductive structure insitu.
The thwartwise section of Associate in Nursing reproductive structure is microsporangia that more forms a spore sac. The spore sac contains spore grains.
Microsporangia and Microsporogenesis
Microsporogenesis involves the formation of spores from microspore mother cells by cell division.
The structure of reproductive structure: The anther is that the breeding is a part of stamens. every reproductive structure is connected by 2 lobes. Every reproductive structure lobe contains 2 spore chambers settled lengthwise. The spore sac is sufficiently provided with a variety of spore microspores.
Structure of Microsporangia
Microsporangia consist of:
Tarentum
The cells are multinucleated and this layer is one in every of the innermost layers of the wall.
Middle layer
It is composed of three to four layers of thin-walled cells. they’re settled simply below the epithelium.
Endothecium
This layer is inner to the cuticle. Some cells develop cells of the epithelium.
Epidermis
It is a protecting outermost single-layer. Cells of the cuticle in genus Arceuthobium develop a fibrous thickening and therefore the cuticle is selected as exothecium.
Formation of spore grains
The young reproductive structure before long becomes four-lobed because it contains a standardized mass of parenchymatous cells engirdled by the cuticle. Every cell at first gift in layer cells divides into the inner primary reproductive structure cell and outer primary membrane bone cell. every primary reproductive structure cell splits to supply microsporocytes. every spore cell meiotically divides to make spore grains.
Microgametogenesis (Development of Male Gametophyte)
Spore is partly developed at this stage and it is the primary cell of the male flora. The wall of the spore grain contains exine (outer layer) and inline (inner layer). The outer layer contains sporopollenin and therefore the inner layer is formed from pectose and polysaccharide.
Pre-pollination development
The microspores begin to germinate in place. A smaller generative cell lies next to the reproductive structure wall. A callose layer is placed round the generative cell. Then, the callose layer dissolves. The reproductive structure then sheds the spore grains. The discharged spore grains are passed to the stigma through fertilisation. The spore grain gift on the stigma absorbs water and at intervals some minutes, swells up. The wall of plant structure secretes hydrolytic enzymes and exogenous pectinases making a passage to enter. The generative and vegetative cells are equipped by the plant structure. The generative cell splits forming 2 non-motile male gametes. Tube nucleus might disintegrate as there’s no vital operation.
Gynoecium
It is the feminine sex organ and therefore the last whorl of the flower. It is composed of reproductive structure and occupies the central position of the neural structure. The stigma, style, and ovary are the parts of the reproductive structure. The ovary produces ovules internally. Through meiosis, ovules turn out megaspores that successively develop into feminine gametophytes. As a result, egg cells are made.
Gynoecium will be:
Monocarpellary
The gametoecium consists of one reproductive structure. For eg., peas and beans.
Multicarpellary
Here, gametoecium contains quite one reproductive structure.
Syncarpous
It is the gametoecium with combined reproductive structure. For eg., Tomato, cucumber.
Apocarpous
It is the gametoecium with free reproductive structure. For eg., Lotus dicot genus.
Pistil- Every reproductive structure has 3 parts:
- Ovary: The ovary could be a chamber wherever ovules (eggs) ar keep, expecting fertilisation.
- Stigma: it is hooked up to the highest of the pistil, wherever the spore from alternative flowers lands.
- Style: it is a hollow structure that connects the ovary and therefore the stigma. It is answerable for the transportation of spore from the stigma to the ovary and holding the stigma in situ.
Megasporangia and Megasporogenesis
The ovule is connected to the placenta with a stalk known as funiculus. It yields megasporocytes that kind megaspores. Megasporogenesis is the method of arrangement of microspores of the megaspore cell. The microspore cell divides meiotically. one in every of the 3 megaspores is used whereas the others degenerate. The useful macrospore forms the feminine flora.
Pollination is an ecological method administered by all flowering plants. During this method, the matured spore grains are transferred from the reproductive structure to the stigma for the aim of amphimixis in flowering plants.
Sorts of pollination
- Self-Pollination: This method happens once the spore grains from the reproductive structure are deposited on the stigma of a constant flower, or another flower on a constant plant.
- Cross-Pollination: This method happens once the spore grains ar transferred from the reproductive structure of 1 flower into the stigma of another flower of various plants of constant species.
Conclusion
After fertilisation, the pollen is transferred to the ovary through the plant structure. Once reaching the ovary, one in every of the male gametes mates with the ovule, or the feminine sex cell (fertilisation) and therefore the alternative joins with the polar nuclei. The sex cell uniting with the eggs leads to the assembly of a fertilized ovum, that gently develops to be Associate in Nursing embryo. The second sex cell that unites with the polar nuclei leads to the formation of reproductive structure nucleus. It provides nourishment to the embryo. The fertilisation ultimately turns ovules into seeds whereas the ovary develops into the fruit.