Question
Write a short note on Apomixis and polyembryony.
✓
Answer
→ Seeds in general are the products of fertilisation, but in a few flowering plants such as some species of Asteraceae and grasses a special mechanism, to produce seeds without fertilisation, called apomixis have evolved.
→ Thus, apomixis is a form of asexual reproduction that mimics sexual reproduction.
→ Types: There are several ways of development of apomictic seeds.
(i) Recurrent agamospermy:
→ In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation.
(ii) Adventive embryony:
→ More often, as in many citrus and mango varieties some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos.
→ In such species each ovule contains many embryos. Occurrence of more than one embryo in a seed is referred to as polyembryony.
→ Thus, apomixis is a form of asexual reproduction that mimics sexual reproduction.
→ Types: There are several ways of development of apomictic seeds.
(i) Recurrent agamospermy:
→ In some species, the diploid egg cell is formed without reduction division and develops into the embryo without fertilisation.
(ii) Adventive embryony:
→ More often, as in many citrus and mango varieties some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac and develop into the embryos.
→ In such species each ovule contains many embryos. Occurrence of more than one embryo in a seed is referred to as polyembryony.
Need a full question paper?
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
Explore more
Similar questions
Expand the following:
- ICSI.
- GIFT.
- ZIFT.
- IUT.
- IUI.
- IVF.
State the functions of acrosome.
Briefly explain IVF and ET. What are the conditions in which these methods are advised?
The graph given below shows species-area relationship of a certain region.
a. Study the graph and explain what it represents.
b. After a while, a small area was taken for constructing a road which divided the region into two. Write the impact this construction would have on species richness of the region.
a. Study the graph and explain what it represents.
b. After a while, a small area was taken for constructing a road which divided the region into two. Write the impact this construction would have on species richness of the region.
A large number of married couples the world over are childless. It is shocking to know that in India the female partner is often blamed for the couple being childless.
Suggest a technique that can help the couple to have a child where the problem is with the male partner.
Suggest a technique that can help the couple to have a child where the problem is with the male partner.
Observe the diagram of Genetic code and answer the following questions:
i. How many codons codes for amino acids and how many do not?
ii. Explain the following giving one example of each.
a. Unambiguous and specific codon
b. Degeneration codon
c. Universal codon
d. Initiator codon
i. How many codons codes for amino acids and how many do not?
ii. Explain the following giving one example of each.
a. Unambiguous and specific codon
b. Degeneration codon
c. Universal codon
d. Initiator codon
- Mention the exact location or the site in a flowering plant, where the following developments take place:
- Deposition of sporopollenin.
- Triple fusion.
- Release of male gametes.
- Megasporogenesis.
- Draw a labelled diagram of a male gametophyte of an angiosperm.
How are assisted reproductive technologies helpful to humans? How are ZIFT and GIFT different from intra uterine transfers? Explain.
Why are the conventional methods not suitable for the assessment of biodiversity of bacteria?
Look at the figure below depicting lac operon of E.coli.
i. What could be the series of events when an inducer is present in the medium in which E.coli is growing?
ii. Name the inducer.
i. What could be the series of events when an inducer is present in the medium in which E.coli is growing?
ii. Name the inducer.