Flower and pollination - class-XII

Flower is a reproductive organ. Essential parts of a flower include the stamens (male parts) and the carpels (female parts). It takes part in the process of pollination which results into the completion of reproduction. Pollen grains transfer from anther to carpel resulting into the formation of seeds and fruit.

Asteraceae or Composite is large and it is an economically important family of flowering plants. In Asteraceae, the flowers are bracteates, sessile, complete (flower having calyx, corolla, stamens, and pistil) As well as hermaphrodite (i.e. bisexual), pentamerous (i.e. calyx, corolla, androecium, and gynoecium), actinomorphic i.e. radial symmetry, and epigynous ovary enclosed in the receptacle with stamens. So, the correct answer is ‘Flowers are hypogynous in Asteraceae’.

So option B is correct.

Flowers are used by the plants for sexual reproduction. Actually, every single part of a flower is used only for reproduction. Flowers care about making themselves beautiful for one purpose to attract a mate, and hence to reproduce.

The correct answer is B.

The flower is a reproductive organ of an angiosperm plant. The typical flowers consist of sepals, petals, stamens, and carpels. A flower having both stamens as well as carpels or pistils is known as a bisexual flower. Flowers that are either staminate (means having stamens) or pistillate (having pistils only) are known as unisexual flowers. Thus the answer is unisexual flowers.

The correct option is B.

• Anthocyanins are red or purple colored water-soluble pigments present in the plant cell vacuoles. 
• They are responsible for the color of the flowers, fruits as well as leaves. But, phycoerythrin is a photosynthetic pigment and it is found in red algae.
• Carotenes and Xanthophylls both are carotenoid pigments of higher plants. They are accessory photosynthetic pigments.
• The correct option is C.

Most of the night flowers are white emerges better in low light conditions. Hence making it simpler for insects to discover. As they bloom at night the plant does not have to waste resources producing coloured pigments to attract the day insects. Night blossoming blooms are ordinarily and vigorously scented. Then it goes about as an attractant for nighttime insects and mammals.

Thus the correct answer is option D.

Vallisneria is a submerged hydrophyte and it is a dioecious plant with the flowers borne under the water. The male flowers detach on the maturity and float on the surface of the water whereas the female flowers grow under the water. They come up to the surface with the help of their thin long stalk. 

The male flowers of Vallisneria are floating on the surface of the water, with the help of two tepals forming boat-shaped float while the third smaller one functions as a rudder.

So, the correct answer is D.

Degeneria is a genus of primitive flowering plants in the family Degeneriaceae, often cited in botany for having primitive stamen structures.

In an inferior ovary (epigynous flower), the thalamus grows upward to surround the ovary, and other floral parts (sepals, petals, stamens) are attached above the ovary.

The tallest flower is amorphophallus which is commonly known as Rafflesia flower. It is known to be the largest flower in the world.

Pollen kitt is a sticky, oily substance found on the surface of pollen grains in insect-pollinated (entomophilous) plants, helping them adhere to insects.

A scape is a leafless flowering stem that emerges directly from the ground or a bulb, common in plants like onions and lilies.

• Ornithophily means bird pollination,  is the pollination of flowering plants by birds.
• Pollination done by Bats is known as chiropterophily. Various fruits are dependent on bats for pollination, such as mangoes, guavas, and banana. Bat pollination is an essential process in tropical communities with 500 tropical plant species. They are completely, or partially, dependent on bats for pollination.
• Malacophily refers to pollination by snails.
• Anemophily or wind pollination refers to a form of pollination whereby pollen is distributed by wind.

So, The correct answer is option B

When a pollen grain from a stamen is transferred
to the stigma of the same plant, it is called self-pollination. It mainly occurs in bisexual flowers.

Chasmogamy is a plant with a reproductive mechanism in which pollination occurs in chasmogamous flowers. Chasmogamous flowers are showy with open petals and encircling exposed reproductive parts.  Chasmogamous stems from Greek for an open marriage. These are named after the open arrangement of floral structures. 

Once chasmogamous flowers have reached maturity, they unfurl and their stamens and/or style are made available for pollinations correct answer is Chasmogamy, is pollination in open flower.

Thus the correct answer is C.

Mixed pollination, involving the application of compatible pollen alongside incompatible pollen, can sometimes overcome self-incompatibility barriers in plants.

Bombax ceiba (the silk cotton tree) is well-known for being pollinated by bats, a process known as chiropterophily.

Anemophilous flowers have certain characters like:-

The pollen grains which are very light in weight can be passed on by wind from one flower to another or to the stigma of the same flower. This is known as wind pollination. They produce light weight pollens in large number and do not produce vector. The stigma is sticky.

Yucca is the pollinated by a moth known as the Tegeticulla yuccasella.  Each spring, adult moths emerge from the underground cocoons. And the males and females meet up with each other on Yucca plants for mating.

The Yucca moth is also termed as the pronuba moth. It is a small white moth that lives in the semi-arid habitats where Yucca plants grow.

Thus the correct answer is A.

Bat-pollinated flowers tend to be large and showy, white or light coloured, open at night and have strong musty odours. They are often large and bell-shaped or a ball of stamens. Flowers are typically borne away from the trunk or other obstructions. More than 500 species of plants, spanning 67 plant families, are pollinated by bats. This pollination syndrome is known as chiropterophily. In general, flowers that use this approach tend to be white or dull in colour, open at night, rich with nectar, and musty or rotten smell. 

Even in absence of pollinating agents, seed setting is assured in Commelina, which is also called as 'Asiatic dayflower'. They lack nectar, they offer only pollen as a reward to their visitors. To attract pollinators, the plant has three types of brightly coloured floral organs: the large blue petals, fertile yellow anthers and infertile yellow antherodes that lack pollen.

Bombax, Butea, and Bauhinia are all typically pollinated by birds (ornithophily).

Hypohydrogamous pollination occurs underwater, which is characteristic of Vallisneria (though it is often cited as epihydrogamous, some sources classify it under underwater mechanisms).

In ferns spores are haploid hence they have half number of chromosomes where as embryo is diploid.

The outer surface of seed shows a scar or mark of attachment with the seed stalk. It is called hilum. There is small pore, called micropyle, which represent the micropyle of ovule.

A. Funiculus- It is the stalk like structure which attaches the ovule to the placenta.

Double fertilization in angiosperms triggers the transformation of ovule into a seed. The zygote delvelops into an embryo. In double fertilization, one male gamete fuses with the egg to form the diploid zygote, the other male gamete fuses with the two polar nuclei to form the triploid primary endosperm nucleus.

A. The nucellus is generally used up
during the development of embryo, but in some cases, it remains outside the
endosperm in the form of a thin layer, called perisperm.

B. Integuments- These are outer covering of ovule which provide protection to the developing embryo.

C. Pericarp or fruit developed from wall of the ovary.

In the development of the dicot embryo, the apical octant of the proembryo gives rise to the plumule and cotyledons.