Sexual Reproduction in Flowering Plants Mind map Class 12 NEET CBSE boards

Flowering plants are also known as angiosperms because they are only kind of plants that produce flower.

In the classification system given by RH Whittaker, there are five types of plants that we have to study for class 12th or neet exam. These are algae Bryophytes, Pteridophytes, Gymnosperm and Angiosperm. 

Flowers are used since long time to convey important feelings such as love, happiness,  affection, grief, peace, etc.

For angiosperm plants, flowers are the site of sexual reproduction. The flowers can have both male and female sex organs or they can be unisexual. Typical flower have four whorls, these are - Calyx, Corolla, Gynoecium and Androecium.

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Pre fertilization structure and events -

In flower the male reproductive organ is androecium and the female reproductive organ is Gynoecium.

The male reproductive organ have stamen which have two part - anther and filament. The anther is a bilobed, dithecous and tetrasporangiate structure. Two microsporangia are found in each lobe located at corner. This microspongia developed further and become pollen sacs. Pollen sacs are also known as male gametophyte. 

The size of pollen grain is about 25 to 50 micrometers in diameter. In more than 60% of angiosperm the pollen grains are shed at 2 celled stage. In the remaining species the generative cell divided and form two male gametophyte before pollen grain are shed. 

Parthenium aur carrot grass, that came into India as contaminant with wheat is notorious to causing pollen allergy.

The Pollen viability is time period for which the Pollen remains active before it lands on a stigma. Pollen grains of wheat and rice lose viability within 30 minutes of the release.

Pistil or Carpel is unit of Gynoecium. A pistil has three parts, these are stigma, style and ovary. Embryo sac is also called as female gametophyte. A mature embryo sac is 7 celled and 8 nucleated.

The transfer of pollen grains from anther to stigma is called pollination. There are three different types of pollination these are

Autogamy - when transfer happens within same flower of the same plant.

Geitonogamy - when transfer happens between different flower but on the same plant.

Xenogamy - when transfer happens on other flower as well as, this flower must be on different plant.

Honey bees are major pollination agent.

Out of the two male gamete that are in pollen grain, one is fused to egg cell and the other is fused with polar nuclei. This two type of fertilization is known as double fertilization.

The result of the sexual reproduction in flowering plants is the seed. If the seed is found without fertilization it is known as apomixis. Apomixis is seen in grasses.

 When the fruit is formed without fertilization it is known as parthenocarpic fruit. Parthenocarpic can be seen in seedless plants like banana.

Some of the flowering plants can produce more than one embryo in their seed this phenomena is called as polyembryony.

If a fruit develops from any other part then ovule then it is called as false fruit. For example the fruit of Apple and strawberry develops from thalamus and hence these are false fruit.

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