Support and transport in plants

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Slide 24

Phloem tissue

Slide 25

The function of phloem tissue

The sieve tubes transport manufactured food from the leaves to the all parts of the plant.

The companion cells probably control the activities of the sieve tubes

Slide 26

Collenchyma and Sclerenchyma

Slide 27

Absorption and Transport of water and mineral salts by plants

Water enters the root hairs of the epidermis of roots by osmosis

POINTS TO REMEMBER

THE SOIL WATER IS THE DILUTE SOLUTION

THE CELL SAP HAS CONCENTRATION SOLUTION BECAUSE OF HIGH CONCENTRATION OF SALTS.

THE CELL MEMBRANE AND TONOPLAST IS SEMI-PERMEABLE MEMBRANE

OSMOSIS: MOVEMENT OF WATER MOLECULES FROM HIGH

WATER POTENTIAL TO LOW WATER POTENTIAL

THROUGH SEMI PERMEABLE MEMBRANE.

Slide 28

Lateral transport of water and mineral salts to the stele of the root

Slide 29

Upward movement of water and mineral salts through the stem from Roots to Leaves

Slide 30

Forces responsible for the upward movement of water

Transpirational pull

Root pressure

Capillarity

Slide 31

Forces responsible for the upward movement of water

Transpirational Pull:

Water evaporates from leaves

Creates diffusion pressure gradient between outside air and xylem

Tension exists in the water column extending from the roots to the leaves

Adhesive and cohesive forces keep the column continuous

Thus water is continually being pulled upward as water evaporates from the leaves

Upward pull = transpirational pull

Slide 32

Forces responsible for the upward movement of water

Root pressure

Cell sap of root hair always has low water potential when compared to soil water

Water enters root hair by osmosis

Continuous osmosis causes pressure forcing water a short distance up the stem

Capillarity

Spontaneous movement of water up narrow tubes because of adhesion and cohesion is called capillarity

Lumen of xylem vessels and tracheids are very narrow therefore capillarity takes place

Upward distance is very short

Slide 33

Structural modifications of leaves to reduce water loss (Internal factors limiting transpiration)