Double fertilization involves

• fertilization of the egg by two male gametes

• fertilization of two eggs in the same embryo sac by two sperms brought by one pollen tube

• fertilization of the egg and the central cell by two sperms brought by different pollen tubes

• fertilization of the egg and the central cell by two sperms brought by the same pollen tube.

The pollen tube usually enters the embryo sac

• through one of the synergids

• by directly penetrating the egg

• between one synergid and central cell

• by knocking off the antipodal cells.

253.

Assertion: Insects visit flowers to gather honey.

Reason: Attraction of flowers prevents the insects from damaging other parts of the plant.

• If both Assertion and Reason are true and Reason is the correct explanation of Assertion

• If both Assertion and Reason are true but Reason is not the correct explanation of Assertion

• If Assertion is true but Reason is false

• If both Assertion and Reason are false.

Pollen grains are able to withstand extremes of temperature and dessication because their exine is composed of

• cutin

• suberin

• sporopollenin

• callose

Assertion: Coconut tree is distributed in coastal areas over a large part of the world.

Reason: Coconut fruit can float and gel dispersed over thousands of kilometers before losing viability.

• If both Assertion and Reason are true and Reason is the correct explanation of Assertion

• If both Assertion and Reason are true but Reason is not the correct explanation of Assertion

• If Assertion is true but Reason is false

• If both Assertion and Reason are false.

When the pollen tube enters through the micropyle, it is termed as

• chalazogamy

• mesogamy

• porogamy

• none of these

For self pollination, flower must be

• unisexual

• bisexual

• monosexual

• asexual

Assertion : Many visitors to the hills suffer from skin and respiratory allergy problem.

Reason : Conifer trees produce a large quantity of wind-borne pollen grains.

• If both Assertion and Reason are true and the reason is the correct explanation of the assertion

• If both Assertion and Reason are true but the reason is not the correct explanation of the assertion

• If Assertion is true statement but Reason is false

• If both Assertion and Reason are false statements

The plant part which consists of two generations, one within the other, is

• genninated pollen grain

• embryo

• unfertilized ovule

• seed

Dispersal of fruits in Opium (poppy) occur through shaking by wind by

• explosive mechanism

• parachute mechanism

• censer mechanism

• jacular mechanism