أحياء لغات – support and movement in the plant للصف الثالث الثانوى 2016

:-Support in Plants-

**The plant possesses different methods and systems for support*:- Why***

1- To maintain its shape.

2- for protection.

These methods

Physiological Structural1

a- Physiological

The cell becomes turgid, when water passes by osmosis into its vacuoles.

As a result, the size and pressure of vacuoles increase, affecting the shape of the cell wall.

Examples

1-The turgidity of the guard cells,

2-The wilting of leaves and stems of herbaceous plants that face drought& The wilting plant will attain its turgidity by soil irrigation.

3- If you soak dried fruit in water, you will notice that it absorbs water, enlarges in size, and swells due to the turgidity of its cells.

BUT , On the contrary, if you leave fresh seeds such as peas or beans for a time, you will notice that the seeds become wrinkled and wilt due to loss of water from their cells.

B. The structural support

Deposition of substances on or in the cell wall. Why?

( 1- Protect the inner plant tissues 2- Prevent the water evaporation)

:-Some examples

Deposited material	Parts
Impermeable cutin	External cell wall (epidermis)
Cellulose only	Collenchyma cell
cellulose and lignin	Sclerenchyma (Fibers and stone cells)
Impermeable Suberin	Cork layer

The position and distribution of thickened cells play a role for support?

Deposition of Hard substance such as cellulose or lignin in cell walls or in some parts so these cells become stronger
Deposition of cutin on the epidermal cells to become Thick &impermeable (Decrease evaporation of water)
Movement in livings organisms

Type of movement	A continuous movement	A positional movement	A total movement
Definition	inside each cell for its biotic activities	Takes place in some organs of living organisms	Movement of the organism from place to place in search of food, or for mate. Spread in nature.
Examples	v Cytoplasmic streaming in plant.

v Blood movement in animals.
v As peristalsis in vertebrate intestines .
v The movement of insectivorous plant leaves.This type of movement is restricted to animals.

Touch movement	Sleep movement	Tropism
Leaves of some plants are affected by touch;

Mechanism :-

when the leaflets of Mimosa are touched, they collapse in successive order followed by the petiole.The leaves of Mimosa, and some leguminous

Mechanism :-
plants partially close during darkness and return back to their original position in the light.
Thus, through the succession of light and dark, movement of the leaves, which is similar to awakening and sleeping, occurs and so this movement is known as sleeping movementwhich is the response of different parts of to plant to light, humidity, and gravity
Mechanism :-
due to the difference in growth rates resulting from the effect of Auxins.
Phototropism
Hydrotropism
Geotropism

4-Cytoplasmic streaming

One of the main characteristic of the living cytoplasm is its continuous rotation inside the cell.

NB) . This is shown when examining Elodea leaf cell, which is an aquatic plant under the high power of the microscope.

NB). We can see the cytoplasm forming a thin layer lining the cell wall and streaming in a rotational movement in one direction But How AS cytoplasm has nocolor? ……This movement is indicated by the movement of the chloroplasts

embedded in the cytoplasm.

أحياء لغات – support and movement in the plant للصف الثالث الثانوى 2016 Hgjtj-625x202

5-Haptotropism: (Pulling movement):

1. Tendrils in Pea:

One special type of movement is Haptotropism, which is seen in tendrils of pea.
Mechanism :-
1-The tendril raises itself into the air and is likely to make contact with a solid object.
2-It twines closely around the object for few turns in a spiral form.
3- Its length decreases, and so the plant stem approaches the support, and grows vertically.
4-The tendril becomes thickened and lays down a considerable amount of mechanical tissue.

What will happen if the tendril doesn’t meet a support during its twining movement?

It wilts and dies.

How can the tendril twist itself around the support?

The twining of the tendril around the support is due to slow growth in the side in contact with the support

Accelerated growth in the far side

This leads to elongation of the far side, and so the tendril twines around the support

أحياء لغات – support and movement in the plant للصف الثالث الثانوى 2016 Gfhyh-378x400

2. Pulling roots of corms and bulbs:

Site:-
Corms and bulbs have pulling roots below them,
Function :-
by contracting of these roots, the corm or bulb is pulled downwards to a suitable level in the soil.
Importance:-
Subterranean storing stems remain at a suitable distance from the soil surface by the help of these pulling roots which support the aerial parts against wind effects.
أحياء لغات – support and movement in the plant للصف الثالث الثانوى 2016 Fnhjfhjyrsj-625x364