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Transpiration

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

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Transpiration

  1. 1. TRANSPIRATION
  2. 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. 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. 4. Experiments to demonstrate transpiration  Some important experiments have done to demonstrate and measure the rate of transpiration.  Some of them are
  5. 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. 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. 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. 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. 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. 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. 11. Lets Recap:-
  12. 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.

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