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501 questions in this collection · Page 10 of 51
Question 91 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
In which one of the following, both autogamy and geitonogamy are prevented?
In several species such as papaya, male and female flowers are present on different plants... This condition prevents both autogamy and geitonogamy.
Question 92 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
An organic substance that can withstand environmental extremes and cannot be degraded by any enzyme is:
No enzyme that degrades sporopollenin is so far known.
Question 93 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Even in absence of pollinating agents seed-setting is assured in:
Commelina produce... cleistogamous flowers... which produce assured seed-set even in the absence of pollinators.
Question 94 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
What is the function of germ pore?
Following compatible pollination, the pollen grain germinates on the stigma to produce a pollen tube through one of the germ pores.
Question 95 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Wind pollination is common in:
Wind-pollination is quite common in grasses.
Question 96 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Nucellar polyembryony is reported in species of:
More often, as in many Citrus and Mango varieties... nucellar cells... develop into the embryos.
Question 97 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Apomictic embryos in Citrus arise from:
Nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos. Nucellus is maternal sporophytic tissue.
Question 98 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Wind pollinated flowers are:
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.
Question 99 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
The nutritive layer of the anther wall is:
The innermost wall layer is the tapetum. It nourishes the developing pollen grains.
Question 100 of 501
📘 CLASS XII
Sexual Reproduction In Flowering Plants
Which one of the following statements is correct?
Tapetum... nourishes the developing pollen grains.