CBSE Questions for Class 12 Medical Biology Sexual Reproduction In Flowering Plants Quiz 6 - MCQExams.com

• The pollination mechanism in Salvia is a unique lever type. The flowers in this genus are arranged in thyrsus inflorescence and they are attractive and well adapted for cross-pollination through the agency of insects. 
• In this lever mechanism of pollination, the Corolla has a spreading upper lip, which acts as a landing place for the insect. When the insects land on the lower lip of the corolla and in its endeavor to obtain nectar that is secreted by the hypogynous disc, pushes the sterile lobes of the stamen inwards.
•  Due to this the upper half of the connective with the fertile lobes acts as a lever. Then the anther lobe comes down and shed the pollen on the back of the insect.

$$\textbf{Correct option: D}$$

$$\textbf{Solution:}$$

Option A:

$$\bullet$$ Pollination by water is called hydrophily and it occurs in aquatic plants mostly.

Option B:

$$\bullet$$ Pollination by animals is called zoophily. Animals like bats, birds, insects, etc do pollination.

Option C:

$$\bullet$$ Pollination by air is called anemophily and the flowers pollinated by air are called anemophilous flowers.

Option D:

$$\bullet$$ Entomophily is the pollination by insects and the flowers pollinated by insects are called entomophilous flowers.

The characteristic features of entomophilous flowers are:

$$\bullet$$ Entomophilous flowers are colored, have fragrance, and produce nectar. Colored flowers and fragrances attract insects towards them for pollination. In return, insects get nectar from these flowers.

$$\bullet$$ Mostly they are large in size. These flowers are often present in inflorescence when small in size.

$$\bullet$$ The pollen grains are heavy and sticky so that they can easily stick with the body of pollinators.

Hence the correct option is option D.

• Pollination is a process of transfer of pollen grain (male gamete) to the stigma (part of the female reproductive unit) which results in fertilisation and formation of seed takes place. 
• The process of pollination takes place with the help of biotic and abiotic agents. 
• The abiotic agents are wind and water while biotic agents are insects, bats, birds, snails, etc. Fruits are produced after fertilisation. 
• Thus, plants can produce fruits with the help of insects as they are pollinators.

• Balsam fruit is composed of pod-like structures. The castor fruit is spherical in shape. 
• On maturity, these fruits dry out and open up. The breaking of the fruits causes an explosion which results in the seeds scattering and disperse. 
• Cotton seeds have hairs over the seeds which help them to be carried away by the wind.
  

• They do not open at all. 
  
• The anthers and stigma lie close to each other.
  
• When anthers dehisce in the flower buds, pollen grains come in contact with the stigma to effect pollination. It is autogamous.
  
• They produce assured seed-set even in the absence of pollinators.
  

• A unisexual flower is a flower that contains three whorls such as petals, sepals, the male reproductive structure (stamen) or the female reproductive structure (pistil). 
• Autogamy is pollination by the transfer of pollen grains from the anther of a flower to the stigma of the same flower.
• Geitonogamy is the pollination by transfer of pollen grains from the anther of a flower to the stigma of another flower of the same plant.
• Thus, a unisexual flower cannot show autogamy but geitonogamy is possible.

• Staminate flower is the one in which androecium is present. Each unit of the androecium is called microsporophyll or stamen. 
• It is the male reproduc­tive organ of the flower. A stamen is made up of a stalk called the filament and anther which contains microsporangia.
  
  Hence, the correct option is A.

• Seed formation without fertilization in flowering plants involves the process of apomixis. 
• 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. It includes abnormal sexual reproduction in which egg or other cells like synergids and antipodals develop into an embryo without fertilization and meiosis.