Post Fertilization: Structure & Events
Good morning Dear Students,
Welcome to our new Academic Session 2020-2021 officially.
Please mark your attendance for today.
Today we will cover the following learning outcomes :-
Students will be able to :
1) Draw & Explain the formation of Endosperm, Embryo & Seed.
2) Understand & Elaborate the process of Apomixis & Polyembryony.
Kindly write your notes in your register & ask your doubts in the blog itself.
POST FERTILIZATION : STRUCTURE & EVENTS
This includes :-
i. Development of Endosperm.
ii. Development of Embryo.
iii. Maturation of Ovules into seed & Ovary into fruits.
DEVELOPMENT OF ENDOSPERM
The PEN divides repeatedly to form a TRIPLOID Endosperm. The cells contains starch, oils & proteins. Endosperm is a source of nutrition for Embryo.
Types of Endosperm Formation
a) Nuclear Type
b) Cellular Type , &
c) Helobial Type.
NUCLEAR TYPE
First division & usually several of the following division are unaccompanied by wall formation. The nuclei may either remain free or in later stages, they may become separated by walls. After sometime the nuclei are being pushed towards the periphery thus a large Central Vacoule is formed.
CELLULAR TYPE
First division & most of the following divisions are accompanied by wall formation. Thusthe sac is divided into several chambers. The first wall is usually transverse, but sometimes vertical or oblique.
P. S. The coconut water from tender coconut that is free nuclear Endosperm ( made up of thousands of nuclei) and the surrounding White Kernel is the cellular Endosperm.
DEVELOPMENT OF EMBRYO
Embryo develops at the micropylar end of the embryosac, where Zygote is situated.
Zygote ----> Proembryo -------> Globular ----->Heart shaped embryo -----------> Mature Embryo. (Mitotic Cell divion).
A Typical Dicot Embryo
A Typical Monocot Embryo
MATURATION OF SEED & FRUIT
THE FRUIT
APOMIXIS
It is the process of reproduction that mimics sexual reproduction I. E without fertilization produces Seeds. Eg : Asteraceae & Grasses (Poaceae)
It occurs in two ways :-
1) ADVENTIVE POLYEMBRYONY - Nucellus cells or integuments which are diploid, continuously divide & enter inside Embro Sac & later develop into Embryo. This gives rise to a POLYEMBRYONY conditions in Citrus, Opuntia etc.
2) RECURRENT AGMOSPERMY - formation of seed that has an embryo formed without meiosis & syngamy. For eg: the diploid Egg as well as other diploid cells of embryo sac can grow into normal Embryos. It is seen in Rubus, Apple, Poa etc.
Advatages of Apomixis.
i. Adventive embryos are better clone than cuttings of plants.
ii. Hybrid varieties provide higher & better yield.
I will be also sending you YouTube link related to this topic for better understanding.
See you on 3rd April Day 2 time table.
Welcome to our new Academic Session 2020-2021 officially.
Please mark your attendance for today.
Today we will cover the following learning outcomes :-
Students will be able to :
1) Draw & Explain the formation of Endosperm, Embryo & Seed.
2) Understand & Elaborate the process of Apomixis & Polyembryony.
Kindly write your notes in your register & ask your doubts in the blog itself.
POST FERTILIZATION : STRUCTURE & EVENTS
This includes :-
i. Development of Endosperm.
ii. Development of Embryo.
iii. Maturation of Ovules into seed & Ovary into fruits.
DEVELOPMENT OF ENDOSPERM
The PEN divides repeatedly to form a TRIPLOID Endosperm. The cells contains starch, oils & proteins. Endosperm is a source of nutrition for Embryo.
Types of Endosperm Formation
a) Nuclear Type
b) Cellular Type , &
c) Helobial Type.
NUCLEAR TYPE
First division & usually several of the following division are unaccompanied by wall formation. The nuclei may either remain free or in later stages, they may become separated by walls. After sometime the nuclei are being pushed towards the periphery thus a large Central Vacoule is formed.
CELLULAR TYPE
First division & most of the following divisions are accompanied by wall formation. Thusthe sac is divided into several chambers. The first wall is usually transverse, but sometimes vertical or oblique.
P. S. The coconut water from tender coconut that is free nuclear Endosperm ( made up of thousands of nuclei) and the surrounding White Kernel is the cellular Endosperm.
DEVELOPMENT OF EMBRYO
Embryo develops at the micropylar end of the embryosac, where Zygote is situated.
Zygote ----> Proembryo -------> Globular ----->Heart shaped embryo -----------> Mature Embryo. (Mitotic Cell divion).
A Typical Dicot Embryo
A Typical Monocot Embryo
MATURATION OF SEED & FRUIT
THE FRUIT
It is the process of reproduction that mimics sexual reproduction I. E without fertilization produces Seeds. Eg : Asteraceae & Grasses (Poaceae)
It occurs in two ways :-
1) ADVENTIVE POLYEMBRYONY - Nucellus cells or integuments which are diploid, continuously divide & enter inside Embro Sac & later develop into Embryo. This gives rise to a POLYEMBRYONY conditions in Citrus, Opuntia etc.
2) RECURRENT AGMOSPERMY - formation of seed that has an embryo formed without meiosis & syngamy. For eg: the diploid Egg as well as other diploid cells of embryo sac can grow into normal Embryos. It is seen in Rubus, Apple, Poa etc.
Advatages of Apomixis.
i. Adventive embryos are better clone than cuttings of plants.
ii. Hybrid varieties provide higher & better yield.
I will be also sending you YouTube link related to this topic for better understanding.
See you on 3rd April Day 2 time table.
Present ma'am
ReplyDeleteGood morning ma'am
ReplyDeleteGood Morning Ma'am
ReplyDeletegood morning ma'am
ReplyDelete-Yashvardhan
ma'am hv you checked the test assignment?
Yes Yashvardhan, Almost every body did a good job. It was important for me to know whether you all understood the topic taught online well or not, and I am glad to see it.
DeleteGood morning ma'am
ReplyDeleteGood morning ma'am
ReplyDeleteGood morning ma'am
ReplyDeleteGood morning maam
ReplyDeleteGood morning, ma'am
ReplyDeleteGood morning to all the students. Kindly go through the blog & ask me questions based on it.
ReplyDeleteAlmost everyone did a fantastic job in test. It was a little feedback for me to check whether you all understood the topic or not, since I am not physically present.
Apomixis & poly embryony can be tricky , so clarify this portion from me.
This portion is usually ask for 3/5 marks questions
Good morning ma'am
ReplyDeleteGood morning ma'am
ReplyDeleteGood morning maam
ReplyDeletepresent ma'am
ReplyDeleteSo I am here waiting for your doubts.????
ReplyDeleteGood morning maam
ReplyDeleteGood morning ma'am
ReplyDeletema'am dont we hv to write about helobial?
ReplyDeleteIt is nit in CBSE syllabus, so for competitive exams you can do that
DeleteGood morning Seedhant & Aadithya. Good to see you
ReplyDeleteMa'am what about fruits like guavas and pomegranate? How are they classified?
ReplyDeleteFalse fruits based on how they originate .
DeleteGood morning ma'am
ReplyDeleteMa'am the embryo will mature when the seed is fully formed right?
ReplyDeleteGood morning ma'am
ReplyDelete