plant movement bio project

8/3/2019 Plant Movement Bio Project

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BIOLOGYPROJECT

NAME: SHAHAB AKHTAR RABBANICLASS: X SEC: G

TOPIC: photosynthesis andplant movements

EXAM NO.: 10722

Photosynthesis and Plant

Movements


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PLANT

MOVEMENTS


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A directional growth or movement made by a part of a

stationary plant in response to environmental stimulus. The

dictionary defines tropism as an orientation of an organism toan external stimuli.

There are numerous types of tropisms : Hydrotropism Phototropism

Geotropism Chemotropism Thigmotropism Heliotropism Thermotropism


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GEOTROPISMGeotropism is the growth of a living organism in response to gravity.

There are two types of geotropisms. They are:

1. Positive geotropism

2. Negative geotropism

Positive Geotropism

It is the growth of an organism (i.e.

plants) towards the centre of the

earth.Negative Geotropism

It is the growth of an organismaway from the centre of the

earth.

An example of geotropism is

given in the picture.

Positive Geotropism

Negative Geotropism


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IMPORTANCE OF

GEOTROPISM

Provides firm anchorage for roots.Ensure the plant can get adequate

supply of water & mineral salts.


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PHOTOTROPISM

The growth response of a living organism onresponse to light direction is called

phototropism. Like geotropism even

phototropism is of 2 types: 1. Positive

2. Negative

In positive phototropism living

organism grow towards the light. For

example- Stems are positively

phototrophic.

In negative phototropism living organisms

grow away from the light. For example- Roots

are negatively phototrophic.

Positive

Phototropism

NegativePhototropism


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IMPORTANCE OF

PHOTOTROPISM

Phototropism enables leaves to be in aposition to receive as much sunlight as possible

for photosynthesis.


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HYDROTROPISM

Hydrotropism is the growth of a living organism

in response to water. Hydrotropism is the

directed growth of the root in relation to the

gradient in moisture. It begins in the root cap

with the sensing of moisture.

Both positive and negative

hydrotropism exist in living

organisms and its direction of

growth depends upon a stimulus or

gradient in water concentration.

Growing towards water (Positive

Hydrotropism)

Growing away from water

(Negative Hydrotropism)


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IMPORTANCE OF

HYDROTROPISM

Ensures that a plant gets enough water

as a raw material for photosynthesis &enough mineral salts to maintain normal

growth


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Phototropism in ShootPhototropism in ShootThe shoot tip produces auxins which diffuse downward.

The auxins diffuse to the shaded side due to the

presence of unilateral light.

High auxin concentration stimulates growth in shoot.

The shaded side grows faster than the lighted side

The shoot bends towards the light.


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Geotropism in RootGeotropism in Root

Theroot tip produces auxins which diffuse to the elongation region.

The auxins diffuse to the lower sidedue to gravity.

High auxin concentration inhibits growth in root.

The lower side grows slower than the upper side.

The root bends downward


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THIGMOTROPISMThigmotropism is the growth of a living organism

in response to a touch/contact. As in all tropismsthere exist positive and negative thigmotropism.

Positive thigmotropism is where a

living organism grows and clings

to a wall or a fence.

Negative thigmotropism is the

opposite. It is where a living organism

grows away from a touching object.

A thigmotropic plant


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HELIOTROPISM

Heliotropism is quite similar to phototropism. Now, as we knowthat phototropism is the response of a living organism in response

to light but heliotropism is the diurnal motion of the plant flowers or

leaves in response to the direction of the sun. The most famous

examples of heliotropism is the sunflower. Heliotropism was first

described by Leonardo Da Vinci.


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THERMOTROPIS

M

Thermotropism is the tendency of plants or other organisms to bend

toward or away from heat as the movement of a plant or plant part inresponse to changes in temperature. A common example is the

curling ofRhododendron leaves in response to cold temperatures.

Thermotropism is often called thermotropic

movement .


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Chemotropism is movement caused by chemical stimulus

in organisms such as bacteria and plants. An example of

chemotropic movement can be seen during the growth of

the pollen tube. This growth of the pollen tube is always

towards the ovules.

Chemotropism

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