Reproduction in flowering plants
Answers are for parents and teachers.
1
A plant has 2N = 18. How many chromosomes has each microspore? How many pollen grains come from 40 spore mother cells?
18 ÷ 2 = 9 chromosomes. 40 × 4 = 160 pollen grains.
2
An ovary has 15 ovules and 11 are fertilized. How many seeds form? How many male nuclei were used altogether? What happens to the other ovules?
11 seeds. Each fertilization of an ovule uses 2 male nuclei: 11 × 2 = 22. The other 15 − 11 = 4 ovules do not become seeds.
3
Describe the path of a pollen tube from the stigma to the egg: which parts of the flower does it pass through, and how does it enter the ovule?
The pollen grain germinates on the stigma. The tube grows down through the style to the ovary and enters the ovule through the micropyle, reaching the embryo sac.
4
Name two parts of a flower that usually wither and fall after fertilization, and say which part ripens into the fruit.
Any two of: calyx, corolla, stamens, style, stigma. The ovary ripens into the fruit.
5
What happens to a flower that is never pollinated and fertilized, and what happens to the ovule and the ovary of a flower that is?
An unpollinated flower withers and drops without making a fruit. In a fertilized flower the ovule becomes a seed and the ovary ripens into a fruit.