@Sexual Reproduction in flowering plants

Flowering plant• Flowering plants are the dominant plant form

on land and they reproduce by sexual means. Often their most distinguishing feature is their reproductive organs, commonly called flowers.

• Flowering plants, also called angiosperms, use a sexual mode of reproduction. Reproduction in plants mainly revolves around the flower, which has both the male and the female gametes. All the parts of a flower aid in the process of reproduction, although some of them are sterile. To understand about sexual reproduction we need to look through its reproductive organ flower.

Flower {reproductive organ}• DIAGRAM 1 :- Stigma

Style

Ovary

Anther

Filament

Flower diagram 2 :-

DIAGRAM 3

FLOWER’S PARTS AND FUNCTIONS

A flower consists of the following parts-Calyx: Commonly known as sepals, these leaf like

structures protects the flower when it develops from a bud.

Corolla: These are the bright and colourful petals of the flower which attract insects and birds, who

are the agents of pollination.Androecium: It is the male reproductive flower

parts, also known as stamens. Stamens consist of two parts:

Anther: This is a four lobed sac-like structure responsible for pollen formation.

Filaments: These thread-like structures are attached to the anther and they keep the anther in

place.

• Gynoecium: Also called carpels or pistils, these are the female reproductive parts of the flower. Carpels are made up of three parts:

• Ovary: The ovary is a chamber where ovules (eggs) are stored, waiting for fertilization.

• Stigma: It is attached to the top of the carpel, where the pollens from other flowers land.

• Style: It is a tubular structure that connects the ovary and the stigma. It is responsible for the transportation of pollens from the stigma to the ovary and holding the stigma in place.

PROCESS OF SEXUAL REPRODUCTION

PROCESS OF SEXUAL REPRODUCTION

• Sexual reproduction in flowering plants Sexual reproduction in flowering plants involves the production of male and involves the production of male and female female gametes, the transfer of the male , the transfer of the male gametes to the female ovules in a process gametes to the female ovules in a process called called pollination. After pollination occurs, . After pollination occurs, fertilization happens and the ovules grow  happens and the ovules grow into seeds within a into seeds within a fruit. After the seeds . After the seeds are ready for are ready for dispersal, the fruit ripens , the fruit ripens and by various means the seeds are freed and by various means the seeds are freed from the fruit and after varying amounts from the fruit and after varying amounts of time and under specific conditions the of time and under specific conditions the seeds seeds germinate and grow into the next  and grow into the next generation.generation.

• The The anther produces male  produces male gametophytes which are  which are pollen grains, , which attach to the stigma on top of a which attach to the stigma on top of a carpel, in which the female , in which the female gametophytes (inside ovules) are gametophytes (inside ovules) are located. After the pollen tube grows located. After the pollen tube grows through the carpel's style, the sperm through the carpel's style, the sperm from the pollen grain migrate into the from the pollen grain migrate into the ovule to fertilize the egg cell and central ovule to fertilize the egg cell and central cell within the female gametophyte in a cell within the female gametophyte in a process termed process termed double fertilization. .

• The resulting zygote develops into an The resulting zygote develops into an embryo, while the triploid endosperm embryo, while the triploid endosperm (one sperm cell plus a binucleate female (one sperm cell plus a binucleate female cell) and female tissues of the ovule give cell) and female tissues of the ovule give rise to the surrounding tissues in the rise to the surrounding tissues in the developing seed. The ovary, which developing seed. The ovary, which produced the female gametophyte(s), produced the female gametophyte(s), then grows into a then grows into a fruit, which surrounds , which surrounds the seed(s). Plants may either the seed(s). Plants may either self-pollinate or  or cross-pollinate.

Pollination• Pollination is the process where mature

pollens are transferred to the stigma for the purpose of sexual reproduction in flowering plants. It can happen in two ways-

• Cross-Pollination: If pollens from the flower of one plant lands on the stigma of another flower of a different plant, it is called Cross-pollination or Birds. Bees, insect and the wind are some of the agents of cross-pollination

• Self-Pollination: If the pollen of a flower is transferred to its own ovary, it is known as Self-pollination, or fertilization.

Self pollination

• Self-pollination is when pollen from the same plant arrives at the stigma of a flower (in flowering plants) or at the ovule (in Gymnosperms). There are two types of self-pollination: In autogamy, pollen is transferred to the stigma of the same flower. In geitonogamy, pollen is transferred from the anther of one flower to the stigma of another flower on the same flowering plant, or from microsporangium to ovule within a single (monoecious) Gymnosperm. Some plants have mechanisms that ensure autogamy, such as flowers that do not open (cleistogamy), or stamens that move to come into contact with the stigma.

• Occurrence• Few plants self-pollinate without the aid

of pollen vectors (such as wind or insects). The mechanism is seen most often in some legumes such as peanuts. In another legume, soybeans, the flowers open and remain receptive to insect cross pollination during the day. If this is not accomplished, the flowers self-pollinate as they are closing. Among other plants that can self-pollinate are many kinds of orchids, peas, sunflowers and tridax.

• Most of the self-pollinating plants have small, relatively inconspicuous flowers that shed pollen directly onto the stigma, sometimes even before the bud opens. Self-pollinated plants expend less energy in the production of pollinator attractants and can grow in areas where the kinds of insects or other animals that might visit them are absent or very scarce—as in the Arctic or at high elevations. Self-pollination limits the variety of progeny and may depress plant vigor. However, self-pollination can be advantageous, allowing plants to spread beyond the range of suitable pollinators or produce offspring in areas where pollinator populations have been greatly reduced or are naturally variable.

Cross pollination

• Cross-pollination, also called allogamy, occurs when pollen is delivered from the stamen of one flower to the stigma of a flower on another plant of the same species.[4] Plants adapted for cross-pollination have several mechanisms to prevent self-pollination; the reproductive organs may be arranged in such a way that self-fertilisation is unlikely, or the stamens and carpels may mature at different times.[4]

Fertilisation• Fertilisation• Only after pollination, when pollen has landed on

the stigma of a suitable flower of the same species, can a chain of events happen that ends in the making of seeds. A pollen grain on the stigma grows a tiny tube, all the way down the style to the ovary. This pollen tube carries a male gamete to meet a female gamete in an ovule. In a process called fertilisation, the two gametes join and their chromosomes combine, so that the fertilised cell contains a normal complement of chromosomes, with some from each parent flower.

• .

• The fertilised ovule goes on to form a seed, which contains a food store and an embryo that will later grow into a new plant. The ovary develops into a fruit to protect the seed. Some flowers, such as avocados, only have one ovule in their ovary, so their fruit only has one seed. Many flowers, such as kiwifruit, have lots of ovules in their ovary, so their fruit contains many seeds.

Process of fertilization• Occur in part :-The pistil

• Process 1

• Process 2

• Process 3

Made by:-