notes of structure and germination of seed

STUCTURE AND GERMINATION OF SEED

SEED :-  it is develop from a mature ovule after fertilization and is usually enclosed within the fruit.

                It is final product of sexual reproduction.

Seed dormancy is defined as a state in which seeds are prevented from germinating even under environmental conditions normally favorable for germination.

Basic structure of seed:-

·         Seed Coat:- it, is the outer protective covering of seed.

It is made up of two layer

o   Testa :- it is outer layer and it is thick, very hard and dry

o   Tegmen:- it is inner layer and it is thin

·         Hilum:- the structure where seed was attached to the ovary wall. it is concave side of the seed.

·         Micropyle:- the opening where pollen tube enters the ovule.

it serves two function:-

Ø  When soaked in water, the seeds absorb water mainly through it and make it available to the embryo for germination.

Ø  Diffusion of respiratory gases for the growing embryo takes place through it.

·         Embryo:-  it is fleshy and soft structure inside the seed coat.

Embryonal axis:- it is the short axis in which  seed leaves and cotyledons are attached. It formed 4 parts

1.       Radical:- it is the lower part of the axis that gives rise to the primary root.

2.       Plumule:- it is the part of the axis between the cotyledon which forms the shoot.

3.       Hypocotyl:- it is the part of the axis of the embryo between the cotyledons and the radical.

4.       Epicotyls:- it is the part lying above the cotyledon. It bears the plumule at its tip.

·         Endosperm:- it is food storing tissue in seed. Infact in coconut the water is nothing it is a endosperm .

TYPES OF SEED

MONOCOTYLEDONOUS SEED 1.       Only one cotyledon present in the embryo. 2.       Cotyledons is thin and small and lacks food materials. 3.       Endosperm is mostly present and stores food. 4.       Radicle is protected by coleorhiza and plumule by coleoptile. 5.       Example:- maize, rice, wheat

DICOTYLEDONOUS SEED 1.       Two lateral cotyledons are present in the embryo axis. 2.       Cotyledons are fleshy and store food. 3.       Endosperm is mostly absent and lacks food. 4.       Coleorhiza and coleoptiles are absent. 5.       Examples :- pea, bean, gram etc.

ALBUMINOUS OR ENDOSPERMIC  SEED 1.       In this seed food is stored in the endosperm 2.       Cotyledons are thin 3.       Example:- In dicoat seed castor, poppy, custard apple In monocoat seed maize, rice, wheat, palm and millets

EXALBUMINOUS OR NONENDOSPERMIC SEED 1.       In this seed food is stored in cotyledons 2.       Cotyledons are fleshy. 3.       Examples:- In dicoat Gram, pea, mango and mustard In monocot seed Vallinsneria, orchids and Amorphophallus.

QUESTION FOR PRACTISE

1.       differentiate between dicot and monocot seed

2.       differentiate between endospermic and non endospermic seed.

3.       Write the function of microplye.

Find out the monocoat and dicoat seed :- maize, rice, Vallinsneria, orchids , Amorphophallus wheat, palm ,millets

STRUCTURE OF BEAN SEED

·         It is dicotyledonous seed.

·         It is kidney shaped and reddish brown in colour.

·         Raphae:-  it is white line which is present on the convex side.

·         Micropyle:- it is a minute pore present at one end of raphae.

·         Hilum:- it is whitish scar present at other end of raphae.

·         Funiculus:- it is the structure where seed is attached to the fruit.

·         Testa:- it is hard and brownish and helps the seed from injury and infection.

·         Tegmen;- it is pale yellow in colour.

·         Radical:- it forms the root.

·         Plumule:- it forms the shoot.

STRUCTURE OF A MAIZE GRAIN

·         It is a monocotyledonous.

·         It is small, one seeded fruit.

·         It is caryopsis.

·         Caryopsis :-  in dry fruit where the seed coat is fused with the wall of the fruit.

·         It is yellowish in colour.

·         It has two unequal portion:-

·         Epithelium:- it is thin layer.

·         Endosperm:- it is the bigger portion which lies towards the broader side. The yellowish endosperm is the food storage tissue of the grain and rich in starch

·         Aleurone layer:- the outermost layer where protein is stored.

·         Embryo:- the endosperm towards the pointed end lies an opaque body called the embryo.

·         Scutellum:- the embryo consists of one large and shield shaped cotyledon. This is also called scutellum.

·         Plumule:- upper end of scutellum

·         Radical:- lower end of scutellum.

·         Coleoptile:- the sheath covering the plumule is known as coleoptile.

·         Coleorhizae:- the sheath covering the radical is known as coleorhizae.

Q . what are the reserve foods in seeds?

Ans. Seed contains starch, oil, proteins and carbohydrate.

Starch:- it found in wheat, rice, barley and oat seeds.

Oil:- it is found in castor, sunflower, groundnut

Protein :- pulses, pea

Carbohydrate:- potato

QUESTION FOR PRACTISE:-

1.       Write the difference between bean seed and a maize seed?

2.       Draw the diagram of bean seed and maize seed?

3.       Define the following:-

Aleurone layer, coleorhizae, coleoptile,

SEED GERMINATION

The process during which the food reserves present in a seed are broken down and the embryo starts to grow is called germination.

·         Nondormant seeds:- the seed which can germinate under favourable condition are called nondormant seeds.

·         Dormant seeds:- the seed which cannot germinate under favourable condition are called dormant seeds.

Q . write the condition under the dormant seeds?

Ans. After the development, the seed growth stops.

The seed now, begins the lose its water content.

The seed coat becomes impermeable to air and moisture.

At this stage, all the physiological activities are very slow and very little food is used.

Even respiration is very slow.

In this dry condition, the seed can remain alive and dormant for long periods.

The seed in this condition are called dormant, and this stage is called dormancy.

Q . define after ripening?

Ans. During the period of dormancy, the seeds undergo certain internal changes called after ripening.

PROCESS OF GERMINATATION

Imbibition of water

Rupture of seed coat

Absorption of water by embryo

Hydrolysis of carbohydrates, lipids and proteins

Transport of nutrients to embryo

 

Cell division and growth of embryo

 

Seedling formation

CONDITION NECESSARY FOR SEED GERMINATION

1.       MOISTURE

2.       TEMPERATURE

3.       OXYGEN

4.       LIGHT

·         MOISTURE :-  In the dormant seeds, the water content is only 10-15%.

Moisture softness the seed coat and the testa.

Seed swell up and embryo breaks through the softened seed coat and comes out easily.

Q . how you prove that water is necessary for seed germination?

Ans. (i) take two petridishes  and mark them as A and B. Spread cotton wool in both the petridishes. Moisten the cotton wool in petridishes A with water.

(ii) place equal no. Of garm seeds in both the petridishes. Keep both the petridishes in a room at normal temperature (25^.C to 30^.C).

(iii)we observe after two days that seeds in petridishes A will germinate whereas seed in petridish B will not germinate.

HYPOGEAL GERMINATATION 1.       The cotyledons remains underground 2.       In this germination epicotyl elongates 3.       Examples :- bean, gourd, castor, cotton and tarmarind.

EPIGEAL GERMINATION 1.       The cotyledons are pushed above the ground. 2.       In this germination hypocotyl elongates 3.       Examples :- gram, pea, maize, rice

ncert based question of evolution for medical prepartation

1.       Stellar distance is measured in :

a) Kilometer       b) Light year

c) Per second     d) None

2.       Darwin scientist worked on, which island for explanation of natural selection ?

a) Malay archipelago      b) Galapago

c) Sumatra                          d) Port Blaier

3.       In the ancestory line of “Tyrannosarus” which ancestor is present?

a) Crocodile               b) Triceratopos

c) Archaeoptryx                      d) Branchyosaurus

4.       During natural selection which variety of Biston betullaria was completely wiped out from England?

a) White winged moth

b) Dark winged moth

c) Both of them

d) None of them

5.       What was the food habit of the original variety of Darwin’s finches from which many other varieties were developed?

a) Seed eater          b) Cactus eater

c) Wood eater        d) Fruit eater

6.       Tasmanian Wolf, Tiger Cat, Sugar glider are example of :

a) Convergent evolution

b) Adaptive radiation

c) Australian marsupials

d) 2 and 3 both

7.       Which of the following statement is true?

a) During evolution, the rate of

    appearance o f new form of

    organisation is linked to the life

    cycle/life span.

b) The essence of Darwinian theory is

    natural selection.

c) Fitness is based on characteristics

    which are inherited.

d) All of them.

8.       What are two main key point of Darwinian theory of natural selection?

a) Branching descent

b) Natural selection

c) Fitness

d) Both 1 and 2

9.       During evolution the first cellular form of the appeared before how many millions years?

a) 2000                  b) 400

c) 100                    d) 50

1.   The biggest dinosaur, which appeared during evolution was:

a) Thecodont     b) Stegosarus

c) Triceratops     d) Tryannosaurus rex

1.   Mutations are:

a) Random          b) Direcionless

c) Both 1 and 2  d) Always small

1.   Fore limbs of whale, bat, cheetah and human are example of:

a) Analogous organ

b) Homologous organ

c) Homoplastic organ

d) Vestigial organ

1.   Hugo de vries called the single step large mutation as:

a) Mutation                        b) Sports

c) Micro evolution           d) Saltation

1.   Stanley Miller performed his experiment for explanation of origin of line, in which year?

a) 1953                                  b) 1970

c) 1870                                  d) 1960

1.   Which was absent in Miller’s experiment?

a) Vacume pump             b) Electrodes

c) Condenser                     d) None

1.   During human evolution the body of which primitive ancestors covered by hairs and walk like gorilla and chimpanzee.

a) Dryopithecus and cromagnon

b) Dryopithecus and Ramapithecus

c) Ramapithecus and Homohabilis

d) Java man and Peking man.

1.   Cranial capacity of homoerectus                      

 Was about :

a) 650-800 cc                      b) 1400 cc

c) 900  cc                              d) 1600 cc

1.   Why pouched mammals are survived in Australia?

a) Divergent evolution

b) Continential drift

c)  Adaptive radiation

d) Convergent evolution

1.   Dianosours disappeared before:

a) 200 million years ago

b) 20 million years ago

c) 65 million years ago

d) 65 billion years ago

2.   The animals which evolved into the first amphibian that lived on both land and water, were :

a) Jawlessfish                    b) Lobefin

c) Ichthyosorus                 d) Shrew

2.   In which type of natural selection the peak gets higher and narrower?

a) Stabilising selection   

b) Directional selection

c) Disruptive selection

d) None of these

2.   Out of the following the theory of natural selection is based on certain observation, which are :

i) Natural resources are limited.

ii) Population are stable in size except

     for seasonal fluctuations.

iii) Members of a population vary in

    characteristics even though key

     look superficially similar.

iv) Most of variations are inheriteted.

a) i, iii, and iv      b) i, ii, iii and iv

c) ii and iii             d) i, ii and iii

2.   The process of evolution of different species in a given geographical area starting from a point and literally radiating to other area is called as :

a) convergent evolution

b) adaptive evolution

c) parallel evolution

d) continental drift

2.   The industrial revolution phenomenon demonstrate :

a) Gene mutation          b) Genetic drift

c) Natural selection       d) Migration

2.   When more than one adaptive radiation appeared to have occurred in an isolated geographical area, it is called as :

a) convergent evolution

b) adaptive evolution

c) parallel evolution

d) continental drift

2.   Out of the following which is an example of convergent evolution ?

A) Eyes of octopus and mammals

B) Flippers of Penguins and Dolphins

C) Sweet potato and potato

a) A and C                            b) A and B

c) B and C                            d) A,B and C

2.   In some animal, the same structure developed along different directions due to adaptations to different needs is called :

a) Divergent evolution

b) Continential drift

c)  Adaptive radiation

d) Convergent evolution

2.   Conventional religious literature tells us about the theory of species creation. Which of the following is/are included in the theory ?

a) All living organism that we see

    today were created as such

b) The diversity was always the same

     since creation and will be the same

     in future.

c) Earth is about 400 years old.

d) All of these

2.   Mostly mutation are :

a) Harmful           b) Useful

c) Recessive       d) Dominant

ANSWER

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