Good morning students, 

Today I am posting important points about Apomixis, Parthenocarpy and Polyembryony. For importance and fruit and seed the points given in textbook form the excellent material for two mark question. There is no need to study any other material for the same. Hope you all are reading  practice questions and trying to attempt them. Underline answers in your textbook that will help you to revise chapter properly.

Apomixis:-

• Formation of one or more embryos through asexual method of reproduction without formation of gametes and  the syngamy or fertilization.
• Unusual asexual reproduction without gametogenesis and syngamy.
• Development of embryo takes place inside the ovule and further ovule develops into seed.
• Apogamy:- Gametophytic organ or cell ( haploid structure)  produces embryo like structure without fertilization.
• Apospory :- Diploid sporophytic cell produces a diploid gametophytic structure without undergoing meiosis. e.g. Mango, Citrus
• It is possible to produce clones.

Types of apomixis:-

a. Recurrent apomixis:-

1. Development of embryo sac takes place from archesporial cell or from some other part of nucellus or sporogenous tissue.
2. The unreduced embryo sac develops from diploid megaspore mother cell ,this is called as diplospory. (Taraxacum)
3. When the nucellar cells give rise to apomictic embryo sac , it is called as apospory.

b. Non-recurrent apomixis:-

1. Usual reduction division in the megaspore mother cell is seen and haploid embryo sac develops.
2. Development of embryo takes place from the egg cell through parthenogenesis i.e. without fertilization or some other haploid cell of gametophytic origin shows apogamy to develop embryo.
3. This process results in development of sterile progeny. e.g. Nicotiana

c. Adventive embryony:-

1. In this type , the embryo develops from somatic cells of nucellus or the fleshy integuments along with the normal zygotic embryo.
2. This leads to polyembryony.
3. e.g. mango, orange, citrus, lemon etc.

Parthenocarpy:-

• Noll coined the term in 1902.
• It is production and development of seedless fruits.
• It can be induced through vegetative or stimulative methods.
• The development is without fertilization.
• Natural Parthenocarpy is due to genetic factors.
• It can be induced using different types of plant growth regulators like auxins .
• It results in development of seedless fruits. e.g. Banana.

Polyembryony:-

1. Development of more than one embryos inside the seed is called as polyembryony.
2. Leeuwenhoek noticed this for the first time in  Citrus .
3. The development of additional embryos is due to differentiation and development of of various maternal and zygotic tissues related with ovule of seed.
4. It may be true or false on the basis of the fact that whether they arise in same embryo sac or in different embryo sac of the same ovule.
5. When the embryo develops directly from the diploid nucellus and the integuments , it is referred as adventive polyembryony. (  Citrus )
6. In some plants zygote or proembryo divides to produce many smaller units , each of which is capable of developing into an embryo. This is called as cleavage polyembryony.
7. Polyembryony increases life span of plant and is also helpful in horticulture.