Control and Co-ordination — BIOLOGY STD 12 Science — Question

How is a transgenic tobacco plant protected against Meloidogyne incognita? Explain the procedure.

Distinguish between : Pharynx and Larynx.

Read the following and answer any four questions from (i) to (v) given below:
Pollen-pistil interaction is the group of events that occur from the time of pollen deposition over the stigma to the time of pollen tube entry into ovule. It is a dynamic process which has checks at several places for promotion or inhibition of pollen growth. Pollen-pistil interaction is a safety measure to ensure that illegitimate crossings do not occur. Compatibility and incompatibility of the pollen-pistil is determined by special proteins. The compatible pollens are able to absorb water and nutrients from the surface of the stigma. They germinate and produce pollen tubes. Pollen tubes grow into the style. Their growth and path through the style are also determined by specific chemicals.

1. Which of the following parts of gynoecium determines the compatible nature of pollen?

1. Stigma.
2. Style.
3. Ovary.
4. Thalamus.

2. In Triforium, which type of self-incompatibility is found?

1. Gametophytic self-incompatibility (GSI).
2. Sporophytic self-incompatibility (SSI).
3. Both GSI and SSI.
4. None of these.

3. Select the incorrect statement.

1. In Asteraceae, incompatibility is due to the genotype of the sporophytic stigmatic tissues.
2. In members of Brassicaceae, incompatibility is due to the genotype of the pollen.
3. Nature has imposed self-incompatibility to avoid highly homozygous individuals, which have a very low survival value.
4. None of these.

4. Which of the following are examples of self incompatibility?

1. Tobacco.
2. Potato.
3. Crucifers.
4. All of these.

5. Given figures show the pollen-stigma interaction, where pollen wall proteins are released onto the pellicle of stigmatic papillae, where a recognition reaction occurs.

Which of the following statements drawn from given figures is incorrect?

1. P indicates compatible reaction in which the pollen tube penetrates the cuticle and grows down the papilla.
2. Development of callose plug between the plasma membrane and pectocellulosic layer of stigmatic papillae results in the incompatibility reaction in Q.
3. A callose plug, which appears at the tip of pollen in Q, is dissolved by callase enzyme secreted by stigma resulting in compatibility reaction.
4. Deposition of callose can be employed as a reliable bioassay to detect compatibility or incompatibility reactions of pollen and stigma.