Question

Given below is a set of information about some fruits and seeds.

Fruit	Fruit and seed formation
P	Nucellar cells surrounding the embryo sac develop into embryos.
Q	Ovary develops into the fruit by the application of growth hormones.
R	Thalamus contributes to fruit formation.
S	Ovary matures into a fruit after fertilisation.

On the basis of the information provided above, answer the following questions with justification for each answer.

1. How many embryo sacs will be present in each ovule of S before maturation and how many egg(s) will be present in each embryo sac when the embryo sac is developed from a single megaspore?    (1)
2. 1. Which of these fruits exhibits polyembryony? Will their embryos exhibit genetic variation? Justify.    (1)
   2. What will be ploidy of the embryonic cells in the above case?    (1)
3. Which of these fruits can be considered as parthenocarpic? Give a reason.    (1)
   OR
4. Which of the fruits P, Q, R or S is a true fruit with seeds? Give a reason.

Answer 1

1. One embryo sac is present in each ovule, and one egg is present in each embryo sac when the embryo sac is developed from a single megaspore.
2. 
   
   1. P exhibits polyembryony due to the presence of more than one embryo in a seed. Embryos developed from nucellar cells by apomixis, a form of asexual reproduction, don’t show genetic variation.
   2. Cells of embryos developed from diploid nucellar cells are diploid (2n), as these are formed by apomixis, a form of asexual reproduction.
3. Fruit Q, because this fruit is developed without fertilisation and will thus be seedless.
4. Fruit S is a true fruit with seeds. True fruits develop from the ripened ovary after fertilisation, and fertilised ovules mature into seeds.