In which one of the following, both autogamy and geitonogamy are prevented?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Papaya
Explanation: In several species such as papaya, male and female flowers are present on different plants... This condition prevents both autogamy and geitonogamy.
An organic substance that can withstand environmental extremes and cannot be degraded by any enzyme is:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Sporopollenin
Explanation: No enzyme that degrades sporopollenin is so far known.
Even in absence of pollinating agents seed-setting is assured in:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: A
Answer: Commelina
Explanation: Commelina produce... cleistogamous flowers... which produce assured seed-set even in the absence of pollinators.
What is the function of germ pore?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: A
Answer: Initiation of pollen tube
Explanation: Following compatible pollination, the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores.
Wind pollination is common in:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: C
Answer: Grasses
Explanation: Wind-pollination is quite common in grasses.
Nucellar polyembryony is reported in species of:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: A
Answer: Citrus
Explanation: More often, as in many Citrus and Mango varieties... nucellar cells... develop into the embryos.
Apomictic embryos in Citrus arise from:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Maternal sporophytic tissue in ovule
Explanation: Nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos. Nucellus is maternal sporophytic tissue.
Wind pollinated flowers are:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Small, producing large number of dry pollen grains
Explanation: Wind pollination also requires that the pollen grains are light and non-sticky... flowers produce enormous amount of pollen... not very colourful and do not produce nectar.
The nutritive layer of the anther wall is:
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: B
Answer: Tapetum
Explanation: The innermost wall layer is the tapetum. It nourishes the developing pollen grains.
Which one of the following statements is correct?
[Sexual-Reproduction-in-Flowering-Plants] [class-xii]
Correct Option: D
Answer: Tapetum nourishes the developing pollen
Explanation: Tapetum... nourishes the developing pollen grains.