This ppt is based on the basic concept of transpiration, which ill help the student for better understand...

1. TRANSPIRATION

2. -: Topics to be covered :-
• What is Transpiration
• Experiments to demonstrate Transpiration
• Kinds of Transpiration
• Mechanism of stomatal Transpiration
• Factor affecting rate of Transpiration

3. What Is Transpiration :-
 Large quantities of water are absorbed by the plants from the
soil but a small amount of it is utilized.
 The excess amount of water is lost from the aerial parts of the
plants in the form of vapour is known as Transpiration.
 Transpiration is the vital physiological process in which the
water is lost from the aerial parts of the plant.
 Transpiration was first worked out by Stephen Hales, an English
clergyman.
 He first gave the idea of loss of water in the form of vapour,
which is still belived.

4. Experiments to demonstrate transpiration
 Some important experiments have done to demonstrate and measure the rate of
transpiration.
 Some of them are

5. Types Of Transpiration
 3 types of Transpiration is found these are;
i. Stomatal transpiration
ii. Cuticular transpiration
iii. Lenticular transpiration
 Stomatal Transpiration:-
The transpiration process which occurs through stomata is called Stomatal
Transpiration. The stomata are found numerously on the leaf surface.

6.  Cuticular Transpiration :-
cuticle is impervious to water still it looses some water i.e. about 10%
of total transpiration.
 Lenticular transpiration :-
Some of the water may be lost by the woody stem through lenticels
which is called as Lenticular transpiration .

7. Mechanism of transpiration :-
 The stomatal transpiration occurs due to the stomatal movement i.e. the mechanism
of opening and closing of stomata.
 Structure of stomata :-
stomata are small minute pore like structure present in surface of leaf
and are guarded by two guard cells.
• According to the number of distribution of Stomata, they are of 3 types i.e.
epistomatal, hypostomatal, amphistomatal respectively.
• Guardcell contain chloroplast, nucleus, contractile vacule.
• Subsidary cell doesnot contain chloroplast .

8. Opening and closing of Stomata :-
 The mechanism of oprning and closing of stomata involves 2 steps;
a) Starch sugar Interconversion Theory
b) ATP-driven proton- K+ Exchange pump
i. Starch sugar Interconversion Theory :-
• According to Liyord (1908);
Starch Sugar
• According to Sayre (1948)
Starch Sugar (at certain pH )
• According to Yin and Tung
(close) Starch glucose-1-phosphate ( open)

9. • According to steward(1964) the starch during day time at pH 7.0
converted to glucose-1-phosphate, which causes the stomata open by
increasing the OP of guard cell.
• During night the glucose-1-phosphate converted into starch, which
causes the stomata close by decreasing the OP of guard cell.

10. ii. ATP-driven proton- K+ Exchange pump :-
 During day:-
6𝐶𝑂2 + 12 H20 𝐶6 𝐻12 𝑂6 + 6𝑂2
𝐶6 𝐻12 𝑂6 Malic Acid
Malic Acid Malate ion + 𝐻+
 During night :-
• As 𝐶𝑂2 is not utilized by photosynthesis during night hence;
6𝐶𝑂2 + 12 H20 Carbonic acid
• Then it forms ABA (Abscisic acid).
• The 𝑘+ are transported back to the guard cell.

11. Lets Recap:-

12. Factor affecting rate of Transpiration :-
 Two important factors are responsible;
a) External Factor
b) Internal Factor
I. External Factor :-
• Atmospheric Humidity is inversely proportional to rate of transpiration.
• Temperature is directly proportional to rate of transpiration.
• Light intensity is directly proportional to rate of transpiration.
• Wind velocity is directly proportional to rate of transpiration.
• Carbon dioxide concentration is inversely proportional to rate of transpiration.
II. Internal Factor :- The factors like structure of leaf area of transpiring surface, number of
stomata, orientation of leaf are included in the category.