Pollination and Fertilization

pollen tube

The grows through the stigma and style by dissolving the tissues with the help of enzymes and reaches the ovary.

Self sterility

: This is a condition in which even if the stigma receives pollen from the anthers of the same flower, the pollen fails to undergo further growth.

pollen grains

The are stick or spiny to enable them to be carried by the insects easily.

Rafflesia

Elephophily is found in whose flowers are very large and are found at ground level.

Scent

and nectar need not be produced by flowers.

Pollen grain

germinates only if it falls on the stigma of the same plant species, otherwise, it disintegrates.

embryo sac

The contains seven (3+3+1) cells 3 cells at the micropylar end- one egg cell and two synergids,

ovule

The is destined to become the seed and the ovary to become the fruit containing the seed inside.

Fertilisation

is the union /fusion of the nuclei of male and female gamete.

Herkogamy

(Mechanical or Structural barriers): In some flowers, the pollen of a flower can not reach the stigma of the same flower.

Artificial pollination

: When man himself transfers pollen to the stigma it is called .

aquatic plants

Water- pollinated (or hydrophilous) flowers are found only in .

Papaya

( usually has separate male and female trees, but less frequently there may also be a hermaphrodite tree bearing both kinds of flowers)

special features

Wind- pollinated (or anemophilous) flowers usually possess showering .

self pollination

Heterostyly: In such flowers, the stigma and anthers grow at different heights which do not favor .

small opening

The integuments leave a(n) in the micropyle at one end (for the entry of the pollen tube)

Pollination

between flowers of the same plant is considered self- pollination on account of the common genetic characteristics- i.e.

mature pollen grain

The is a cell with a double wall- the outer exine and the inner intine.

Unisexuality

: The flowers may be either male or female and they may be borne on separate plants.

central cell

The is different containing two nuclei called polar nuclei.

Pollen

is produced in very large quantities.

modem times

In , artificial pollination (also called artificial crossing) is a standard practice adopted by plant breeders and scientists in their efforts to evolve new varieties.

ovule

The is the inner part of the ovary.

pollen grains

In some plants, the have a specific gravity almost equal to that of water so that they remain floating below the surface of the water.

pollen grain

The falling on the stigma is stimulated to germinate due to the secretion of sugars by the stigma.

pollen grains

The stigmas are feathery and hang out of the flower to trap the .

pollen grain

The is the male gamete.

ovule

Each has one or two protective coverings, the integuments.

Pollen grains

are light, dry, and smooth so that they can easily be carried away by the wind.

pollen grains

The of one flower get attached to the feet of elephants and may be carried to the stigma of another flower when trampled by those feet.

In some rare cases, as in pansy, some flowers growing close to the ground level, do not open at all (cleistogamy, cleisto

closed), the anthers and stigma lie close to each other which mature at the same time, and self-pollination is assured

Unisexuality

The flowers may be either male or female and they may be borne on separate plants

Example

palms and papaya

Dichogamy

(Different timings of maturation of androecium and gynoecium)

Examples

bhindi, sweet peas, salvia, and sunflower

Examples

custard apple, peepal

Self-sterility

This is a  condition in which even if the stigma receives pollen from the anthers of the same flower, the pollen fails to undergo further growth

Examples

ray florets of sunflowers, orchids, etc

Herkogamy (Mechanical or Structural barriers)

In some flowers, the pollen of a flower cannot reach the stigma of the same flower

Heterostyly

In such flowers, the stigma and anthers grow at different heights which do not favor self-pollination

Examples

primrose, oxalis

(Example

Maize)

Example

Vallisneria

Examples

Bignonia, canna

Artificial pollination

When man himself transfers pollen to the stigma it is called artificial pollination

The mature pollen grain is a cell with a double wall

the outer exine and the inner intine

The embryo sac contains seven (3+3+1) cells 3 cells at the micropylar end

one egg cell and two synergids,