Development of Embryo in Flowering Plants

24/08/2020 Vinod 0 Comments

Development of Embryo in Flowering Plants :-

Development of Embryo in Flowering Plants occur at the micropylar end of the embryo sac where the zygote is situated .

  • Most zygotes divide only after certain amount of Endosperm is formed .

Endosperm :-

During the development of Embryo in Flowering Plants the primary endosperm cell divides repeatedly and form a triploid Endosperm tissue .The cells of this tissue are filled with reserve food materials and are used for nutrition of the developing Embryo .

  • Castor and Coconut contains Oily Endosperm .

Types of Endosperm :-

Three main types :-

  1. Nuclear type :- In nuclear type of Endosperm ,the first division of primary Endosperm nucleus and few subsequent nuclear divisions are not accompanied by wall formation . The nuclei produced are free in the cytoplasm of the Embryo sac and wall formation take place later .

Example – Coconut .

2 . Cellular type :- In this case , there is cytokinesis after each nuclear division of Endosperm nucleus . Thus the Endosperm has a cellular form , from the very beginning because first and subsequent divisions are all accompanied by wall formation .

Example – Petunia , Datura etc .

3 . Helobial type :-

It is an intermediate type between the nuclear and cellular type . The first division is accompanied by cytokinesis but the subsequent ones are free nuclear . The chamber towards Chalazal end .

Development of Dicotyledons Embryo :-

PI.6
Fig . 1 . Stages of Development of Embryo in Flowering Plant ( Dicotyledons ) .

The early stages of development of Embryo in Flowering Plants are similar in both monocotyledons and dicotyledons .

  • The zygote gives rise to the proembryo and subsequently to globular , heart shaped and mature Embryo .
  • A typical Dicotyledons Embryo consists of an Embryonal axis and two cotyledons .
  • The portion of Embryonal axis above the level of cotyledons is the epicotyl with terminates with Plumule or Stem tip .
  • The cylindrical portion below the level of Cotyledons is hypocotyl that terminates at it’s lower end in the Radicle or Root tip . The Root tip is covered with a Root cap .

Development of Monocotyledons Embryo :-

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Fig . 2 . Development of Embryo in Flowering Plant ( Monocotyledons ) .

During the development of Embryo in Flowering Plants Embryos of Monocotyledons possess only one Cotyledon . In the Grass Family the Cotyledon is called Scutellum that is situated towards lateral of the Embryonal axis .

  • At it’s lower end , the Embryonal axis has the Radicle and Root Cap enclosed in an Coleprrhiza .
  • The portion of the Embryonal axis above the level of attachment of Scutellum is the epicotyl . It has a Shoot apex .

Also read :- Fertilization & Developement of embryo in humans

Seeds :-

seed structure
Fig . 3 . Anatomy of common bean and corn Seeds .

Seeds are basically very small Embryonic Plants that are enclosed by a covering called Seed coat .

A typical Seed Includes three basic components –

  1. Seed coat :-

The Seed coat refers to the hard or semi hard covering that sheathes a Seed , protective it from fungi , bacteria and various types of diseases .

2 . Cotyledon :-

Cotyledons are the first leaves produced by Plants . They are not considered true leaves and are sometimes referred to as a Seed leaves because they are actually part of the Seed or Embryo of the Plant .

  • The Cotyledons are the simple structures generally thick and swollen due to storage of food reserves .

3 . Embryo axis :-

At the same time Embryonic shoot and root develops as well taken together , they are called the Embryonic axis .

  • The part of the embryonic axis located above the point of attachment of the Cotyledon is called the Epicotyl .
  • The embryonic axis below the Cotyledon attachment site is called the hypocotyl and is the progenitor of the root .

Fruits :-

11 bio chapter 5 fig 15
Fig . 4 . Anatomy of a Fruit ( Mango ) .

During the development of Embryo in Flowering Plants like mangoes the transformation of Ovule into Seeds and Ovary into Fruit proceeds simultaneously .

The Fruit primarily contains two parts – the Pericarp and the Seed . the Pericarp layer is actually the outer wall of the Ovary from which the Fruit developed .

  • The Pericarp has three layers –

1 . Exocarp or Epicarp :-

This is the outermost layer of Pericarp that forms the skin of the Fruit .

2 . Mesocarp :-

It is the thick , fleshy and juicy middle layer of the Pericarp .

3 . Endocarp :- It is the innermost layer of the Fruit which often develops into the Pith .

True Fruits :-

It is the Fruit that is formed from the fertilized Ovary of the Flower and Ovules get transformed into Seeds .

  • True Fruits are made up of two parts namely Pericarp and Seed .
  • True Fruits can be simple Fruits , Aggregate Fruits and Multiple Fruits .
  • Based on the Pericarp simple Fruits can be classified into two types which include Fleshy Fruits Dry Fruits .

Fleshy Fruits :- Examples – Mango , Berry , Grape ,Orange etc .

Dry Fruits :- Examples – Achene , But Grain Samara etc .

Aggregate Fruits :- Example – Raspberry ,

Multiple Fruits :- Examples – Mulberry , Figs etc .

False Fruits ( Parthenocarpy ) :-

It is the phenomenon in which Fruits are formed without Fertilization .

Fals Fruits arises from other Floral parts except the Ovary .These Fruits are Seedless .

Examples – Apple , Pineapple , Banana ,Strawberry , Akharot , kaju etc .

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