Railway Science (Biology-Reproduction in Plant) (Part-II)

Flowers are the specialized reproductive structures of angiosperms (flowering plants). The stamen is the male reproductive part of the flower. The pistil is the female reproductive part of the flower.

Pollination is the characteristics of flowering plants i.e. Angiosperms. This process involves the transfer of pollen grains from the male reproductive organ (stamen) to the female reproductive organ (pistil) of the same or another flower, leading to fertilization and seed formation. Angiosperms have evolved various mechanisms for pollination, including wind insects, birds and other animals.

Jasmine: Reproduces vegetatively through cuttings, suckers, or grafting, as its flowers often lack fertile pollen or ovules. Watermelon, mustard, and mango : These plants reproduce sexually through seeds. They produce flowers, and the fertilization of the ovule by pollen leads to seed formation.

Bisexual flowers have both pistils and stamens in one flower. These are also called androgynous and hermaphrodite flowers. Examples of bisexual flowers are - Rose, Lily, Tulip, Hibiscus, Sunflower.
The flowers which include only the male (stamen) or female (Pistil) reproductive organs are called unisexual flowers. Examples are Papaya, Coconut flower, Cucumber.

Ovules - The organ that forms the seeds of flowering plants. Sepals - These are the small, leaf-like parts growing at the base of the petals. Petals: This layer lies just above the sepal layer (collectively known as the corolla).
Pollen grains - Haploid microgametophytes that transport male reproductive cells (gametes) in a plant.

Spermatophytes, which means “seed-producing plants”. Pollen tubes act as conduits to transport the male gamete cells from the pollen grain.

Stamens: Representing the male reproductive organ and the gynoecium represents the female reproductive organ. The number and length of stamens are variable in flowers of different species. Types of Stamen - Polyandrous, Monadelphous, Diadelphous, Polyadelphous, Syngenesious, Synandrous.

Pollen grains of wind-pollinated flowers are produced in large quantities to make sure that at least some pollen grains reach the stigmas of other flowers and successful pollination takes place.
Stigma is large and feathery to catch the wind pollen grains. Agents for pollination: Anemophily (Pollination by air/wind), Hydrophily (by water), Entomophily (by Insects), Ornithophily (by birds).

A typical flower has four main parts. The outermost whorl of the flowering plant is calyx and sepals are the floral leaves of this whorl. The second whorl is corolla and petals are floral leaves here.
The third whorl is Androecium, which is the male reproductive organ. The floral leaves here are stamens. The fourth (central) whorl is gynoecium and it is the female reproductive organ of the flower. The floral leaves in it are carpels.

Agents of Pollination - The agents or media which can transfer the pollen grains for pollination. Examples - Air, water, animals and insects. Pollination by air - Light and dry pollen grains are carried by air to the other plants. Pollination by water - Pollen or the male flower is carried by water current towards the female flower to pollinate.
Pollination by insects - The bright colors of corolla and nectar attract the insects and pollen grains stick to the body of the insect which facilitates pollination as it approaches another flower. Pollination by animals - Animals and birds interact with the flowers helping with pollination.