Sexual Reproduction in Flowering Plants Test - 9

The flowers are considered as the reproductive parts of the plants. The female reproductive organs are known as pistils which consist of the style, stigma and ovary. The male reproductive organs are known as a stamen which is composed of the anther and filament.

Plumed seeds occur in Calotropis. The seeds are compressed, broadly ovoid, with a tufted micropylar coma of long silky hair. The crown of the hair on the seeds favouring anemochory gives the plumed appearance.

In some flowers like Cassia and Canna, the stamen does not develop the fertile anther and such a stamen is called staminode. The staminode can become petaloid, as seen in Canna.

Endosperm is a triploid tissue in angiosperms because double fertilization results in the formation of a diploid zygote and a triploid endosperm. The female gametophyte or embryo sac has an egg nucleus and two polar nuclei. One sperm fertilizes the egg nucleus and forms the zygote, 2n. Another sperm joins the two polar nuclei forming the triploid (3n) nutritive tissue, called the endosperm.

• Pollination which occurs by means of insects is known as Entomophily.
• Pollination which occurs by means of birds is known as Ornithophily.
• Pollination which occurs by means of bats is known as Chiropterophily.
• Pollination which occurs by means of snails and slugs is known as Malacophily.

In pea, bean and groundnut, endosperm is consumed by developing embryo in the seed. The endosperm is completely absorbed by the growing embryo and the food reserve gets stored in the cotyledons. Such seeds are called non-endospermic or exalbuminous.

Apomixis' term was given by Winkler (1908). Apomixis in a plant means the development of a new plant without the fusion of gametes. Although seeds, in general, are the products of fertilization, a few flowering plants such as Asteraceae and grasses, have evolved this special mechanism. An apomixis is a form of asexual reproduction that mimics sexual reproduction.

Maize which is also known as Corn plant is pollinated by wind. The anthers are born in long tassels that move with the wind and shake off their pollen. The stigma is feathery and hairy so as to catch the wind-borne pollen. Thus, in maize, pollens are transferred from the anthers of one plant to the stigma of another plant by means of wind i.e. cross-pollination occurs by the wind.

Most angiosperms are adapted to biotic pollination, in which pollen is delivered to stigmas by various animals. The majority of gymnosperms are pollinated by means of wind (i.e., anemophily).

• Apomixis in flowering plants is defined as the asexual formation of a seed from the maternal tissues of the ovule, avoiding the processes of meiosis and fertilization, leading to embryo development. 
• Apomixis relates to mechanisms where an embryo sac is mitotically formed from a diploid cell in the ovule, bypassing meiosis. The genetic nature of plants produced by apomictic embryos is the same as that of parents so they can be called clones.
• Hence, the mother cell is diploid, so diploid embryo forms.

Pollen wall consists of two layers: outer layer exine and inner layer intine.

Exine is made up of sporopollenin which is one of the most resistant known biological materials. Exine is thin in the beginning but it becomes very thick with maturity. However, exine is discontinuous or ruptured at some places. These are the called the germ pores (or germinal furrow) through which pollen tube comes out during germination on the stigma.

• Mulberry is pollinated by wind.

• Cucumber is pollinated by bees.

• Maize is pollinated by wind.

• Vallisneria is pollinated by water.

Hence, animal vector is required for the pollination of Cucumber. So, the correct answer is B.

•Flemming in 1882 characterized the animal mitochondria cytologically.

•Ubisch discovered orbicules (also called ubisch bodies) secreted from the Tapetum and how these ubisch bodies help in exine formation. 

•Strasburger while working on Monotropa, observed the actual fusion of the male gamete with the female gamete (i.e. egg) and discovered syngamy.

•Nawaschin while working on Lilium and Fritillaria confirmed syngamy and gave the concept of Triple fusion and double fertilisation.

Puya raimondii, which is also known as 'Queen of the Andes' is the largest inflorescence. It is pollinated by the help of snails and slugs. It is thus called Malacophily. It is classified under spadix inflorescence.