Biology · Sexual Reproduction in Flowering Plants · NEET
The ovule matures into the seed and the ovary develops into the fruit. Both changes happen at the same time. The wall of the ovary becomes the wall of the fruit, called the pericarp. Remember: ovule to seed, ovary to fruit. NEET often flips this to say 'ovule develops into embryo sac' which is wrong, because the embryo sac forms before fertilisation inside the ovule.
Dormancy is a state of inactivity where the embryo's metabolism slows down. As a seed matures its water content drops to about 10 to 15 percent, so it becomes dry and inactive. This lets the seed survive bad conditions and germinate only when moisture, oxygen and suitable temperature are available. Dormancy also lets us store seeds as food all year and to sow crops in the next season, so it is the basis of agriculture.
NCERT lists clear advantages: (1) pollination and fertilisation do not need water, so seed formation is more dependable; (2) seeds have better strategies for dispersal to new habitats and help the species colonise new areas; (3) seeds carry enough food reserves to nourish the young seedling until it can photosynthesise; (4) the hard seed coat protects the young embryo; (5) as products of sexual reproduction, seeds bring new genetic combinations and variations.
In a true fruit, only the ovary wall (pericarp) forms the fruit, as in mango, orange and guava. In a false fruit, the thalamus (receptacle) also becomes fleshy and edible along with the ovary, as in apple, strawberry and cashew. So the presence of the thalamus in the fleshy part is what makes a fruit false. This is a very common NEET figure question.
After the ovary becomes a fruit, many fruits evolve special mechanisms to disperse seeds away from the parent plant. Fleshy fruits like guava, orange and mango attract animals that eat them and carry the seeds away, while dry fruits like groundnut and mustard use wind or other means. Dispersal spreads seeds to new habitats and reduces competition with the parent.
Seed viability varies a lot. In some species seeds lose viability within a few months, while seeds of many species live for several years, and some remain alive for hundreds of years. A famous record is Lupinus arcticus (a lupine) seed excavated from Arctic tundra that still germinated after around 10,000 years. Dehydration and dormancy make this long survival possible.
Which one of the following statements regarding post-fertilization development in flowering plants is incorrect?
Which part of the fruit, labelled in the given figure, makes it a false fruit?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The main body of the seed comes from diploid tissues: the embryo (2n) forms from the diploid zygote, and the seed coat forms from the diploid integuments of the ovule. The endosperm, however, is triploid (3n). So a seed contains tissues of more than one ploidy.
The pericarp is the wall of the fruit, formed from the wall of the ovary after fertilisation. It may be fleshy, as in guava, orange and mango, or dry, as in groundnut and mustard.
When mature seeds dehydrate and enter dormancy, their metabolism slows and they can be stored for long periods without germinating. This lets seeds be used as food throughout the year and be sown to raise a crop in the next season, which is why seed is the basis of agriculture.
Most fruits form after fertilisation, but a few develop without it. These are parthenocarpic fruits, such as banana, and they are seedless. Parthenocarpy can be induced by applying growth hormones.
