This presentation is made as per the B.Sc-III Botany Syllabus of SGBAU Amravati.

1. GOPIKABAI SITARAM GAWANDE
MAHAVIDYALAYA
UMARKHED, DIST. YAVATMAL
NAAC REACCREDITED (3RD CYCLE) GRADE B++ CGPA 2.79
GOPIKABAI SITARAM GAWANDE MAHAVIDYALAYA UMARKHED, DIST. YAVATMAL
PLANT PHYSIOLOGY AND ECOLOGY
BOTANY
B.Sc-III
Semester-V
Presented by—
Mr. Kailash S Sontakke
Assistant Professor
Department of Botany

2. Plant Physiology
 Plant physiology is a branch of study in Botany dealing with the
physiological processes or functions of plants.
 Fundamental processes such as photosynthesis, respiration, plant nutrition,
plant hormone functions, tropisms, nastic movements, photoperiodism,
photomorphogenesis, circadian rhythms, environmental stress physiology,
seed germination, dormancy and stomata function and transpiration, both
parts of plant water relations, are studied in plant physiology.
 Father of Plant Physiology
Stephen Hales
Julius Sachs
 Father of Indian plant physiology
Jagadish Chandra Bose

3. Photosynthesis
 Every Living organism require energy to do work.
 The anabolic process in plants in which the synthesis of carbohydrates
takesplace from simple inorganic materials like CO2 and H2O with the
help of light energy and chlorophyll pigments.
 solar/light energy is converted into chemical energy

4. Overall Equation of Photosynthesis

5. Modes of Nutrition in Plants

6. Chloroplast

7. Chloroplast Structure

8. Thylakoid

10. Photosynthetic Pigments
1) Chlorophyll
 Chlorophyll a - C55H72O5N4Mg
 Chlorophyll b - C55H70O6N4Mg
2) Carotenoids
 Carotenes - C40H56
 Xanthophylls - C40H56O2
3) Phycobillins (Bilioproteins)
 Phycocyanins – C34H44O8N4 615nm
 Phycoerythrins – C34H46O8N4 560nm

11. C55H72O5N4Mg
C55H70O6N4Mg

12. Nature of Light
 Light is a form of Energy
 It Travels as a stream of tiny particles called photons
 A photon contains a quantum of light.

13. Absorption and Action Spectrum
 Out of total sunlight energy only 40% is received by earth, most of
get reflected or scattered in atmosphere.
 Only about 1% of total solar energy received by earth is absorbed
by pigments and utilized in photosynthesis.

14. Absorption Spectrum
 A curve which shows the amount of light absorbed at each wavelength
is termed as Absorption Spectrum
 Max. light absorbed by Chlorophyll pigments at Blue, Violet and Red
wavelength of visible spectrum

15. Action Spectrum
 An action spectrum is the rate of a physiological activity
plotted against wavelength of light.
 The action spectrum indicates the overall rate
of photosynthesis at each wavelength of light.

16. Action Spectrum

17. Mechanism of Photosynthesis
 In 1931, Van Neil proved bacteria used H2S and CO2 to synthesisze carbohydrates as
follows

18. Mechanism of Photosynthesis
 Ruben in 1941, confirmed it in Chlorella.

19. Mechanism of Photosynthesis
 Robert Hill in 1937,

20. Mechanism of Photosynthesis

21. Photosystem-I & II or LHC-I & II
 Reaction Center/Photocenter
 Accessory pigments/ Light harvesting/Antenna molecule
 PS-II or P680
 PS-I or P700

22. Light Harvesting Complex-LHC

23. Photoexcitation of Chlorophyll - a

24. A) Light Reaction/Primary Photochemical Reaction/Hills
Reaction
 Takes place in Grana of Chloroplast
 Light energy is trapped and stored in the form of ATP & NADPH2(Assimilatory
Power)
 Photolysis of water takes place and Oxygen is evolved
I. Absorption of light energy by Chloroplast pigments
II. Transfer of light energy from accessory pigments to Chl-a
III. Activation of Chl-a by photons of light
IV. Photolysis of water & Evolution of Oxygen
V. Electron transport and the production of Assimilatory power

25. Photophosphorylation
 The process of formation of ATP from ADP & iP in chloroplast in presence of
light is called as Photophosphorylation.
 Two types
1. Cyclic Photophosphorylation
2. Non-Cyclic Photophosphorylation

26. Non-Cyclic Photophosphorylation/ Non-Cyclic Electron
Transport/Z Scheme
 Both PS-I & PS-II are involved
 Electrons releasd from PS-II do not return back to PS-II and it is accompanied
with ATP formation, this is called Non-Cyclic photophosphorylation.
 Photolysis of Water takes place

27. Non-Cyclic Photophosphorylation
FNR- ferredoxin NADP+ reductase

28. Photolysis of water

29. Non-Cyclic Photophosphorylation

30. Cyclic Photophosphorylation
 It is a process of photophosphorylation in which an electron expelled by the
excited photo-centre is returned to it after passing through a series of electron
carriers.
 It occurs under conditions of low light intensity, wavelength longer than 680
nm and when CO2 fixation is inhibited.

31. Cyclic Photophosphorylation

32. Cyclic Photophosphorylation

33. Cyclic Vs Non-Cyclic Photophosphorylation

34. Difference between Cyclic and Non-Cyclic Photophosphorylation
Cyclic Photophosphorylation Non-Cyclic Photophosphorylation
Only Photosystem I is involved. Both Photosystem I and II are involved.
P700 is the active reaction centre. P680 is the active reaction centre.
Electrons travel in a cyclic manner. Electrons travel in a non – cyclic
manner.
Electrons revert back to Photosystem I Electrons from Photosystem I are
accepted by NADP.
ATP molecules are produced. Both NADPH and ATP molecules are
produced.
Water is not required. Photolysis of water is present.
NADPH is not synthesized. NADPH is synthesized.
Oxygen is not evolved as the by-product Oxygen is evolved as a by-product.
This process is predominant only in
bacteria.
This process is predominant in all green
plants.

35. B) Dark Reaction/Blackman’s
Reaction/Biosynthetic Phase
 The pathway by which all photosynthetic eukaryotic organisms ultimately
incorporate CO2 into carbohydrate is known as carbon fixation or
photosynthetic carbon reduction (PCR.) cycle or dark reactions.
 Takes place in Stroma of Chloroplast
 Purely enzymatic
 It is independent of light
 Reduction of CO2 takes place with the help of ATP and NADPH2

36. Calvin Cycle/Calvin Benson Cycle/ C3 Cycle
 Proposed by Melvin Calvin.
 Calvin along with A.A. Benson, J. Bassham used radioactive isotope of carbon (C14) in
Chlorella pyrenoidosa and Scenedesmus oblique’s to determine the sequences of dark
reaction.
 For this work Calvin was awarded Nobel prize in 1961.
 Calvin cycle completes in 4 major phases:
 1. Carboxylation phase
 2. Reductive phase
 3. Glycolytic reversal phase (sugar formation phase)
 4. Regeneration phase

41. Quantum Requirement and Quantum Yield:
 The number of photons (or quanta) required to release one molecule of oxygen in
photosynthesis is called as quantum requirement.
 8 photons are required to evolve one molecule of molecular oxygen.
 On the other hand, the number of oxygen molecule released per photon of light in
photosynthesis is called as quantum yield.
 The quantum yield is always in fraction of one.
 1/8 = 0.125 = 12.5% O2.

42. Photorespiration

43. C4 Cycle ( Dicarboxylic acid pthway HSK Pathway or Hatch and Slack Pathway)
 Firstly reported by Hatch, Slack and Kortschak in 1965
 First product of CO2 fixation is a 4-Carbon compound i.e. Oxaloacetic acid
 Plants in tropical and sub tropical regions commonly follow the C4 pathway.
 Found in many plant species of family Poaceae
e.g., Maize, Sorghum, Sugarcane etc and other plants Atriplex, Amaranthus etc.
 All these plants are known as C4 plants and are dishtinguished by
• Absence of photorespiration
• Anatomical similarities of Leaf (Cane Type)
• These plant have Kranz Anatomy.
The plants in which CO2 fixation takes place by Calvin cycle are called C3 plants.

44. Kranz Anatomy in C4 plant leaf
Chloroplast Dimorphism
Mesophyll cells- Small, Granal
chloroplast
Bundle Sheath Cells- Large, Agranal
Chloroplast

45. HS-1:Phosphoenolpyruvate
(PEP) carboxylase
HS-2:NADPH-dependent
malate dehydrogenase
HS-2a Transaminase
HS-3: NADP+ malic enzyme
HS-4: Pyruvate, phosphate
dikinase
HS-1
HS-2
HS-3
HS-4 HS-2a

46. C3 Plants C4 Plants
The primary product obtained is 3- phosphoglyceric acid. The primary product is a 4 carbon compound, oxaloacetate.
Occurs in mesophyll cells. Occurs in mesophyll and bundle sheath cells.
These can be found in cool and wet areas. These can be found in dry areas.
95% of the green plants are C3 plants. 5% of the green plants are C4 plants.
The rate of photorespiration is high. Photorespiration is absent.
Leaves of these plants do not show Kranz anatomy. Leaves of these plants show Kranz anatomy.
Abundant in temperate conditions. Abundant in tropical conditions.
Bundle sheath cells do not contain chloroplasts. Bundle sheath cells contain chloroplasts.
Carbon dioxide fixation occurs only once. Carbon dioxide fixation occurs twice.
All the steps of dark reaction take place in mesophyll cells. The initial steps are carried out in mesophyll cells and the
subsequent steps are carried out in bundle-sheath cells.
The optimum tem[perature for photosynthesis is very low. The optimum temperature for photosynthesis is high.
These evolved 2.5 billion years ago. Evolved 12 million years ago.
Carbon dioxide fixation is slow. Carbon dioxide fixation is faster.
Photosynthesis is inhibited when stomata are closed. Photosynthesis occurs even when stomata are closed.
e.g. Wheat, Rye, Oats, Rice, Cotton, Sunflower,
Chlorella, barley, Peanuts, cotton, sugar beets,
tobacco, spinach, soybeans, and most trees
are C3 plants
e.g. Maize, Sugarcane, Sorghum, Amaranthus.

47. Crassulacean Acid Metabolism (CAM)
 (CAM) is found only in succulents and other xerophytes or plants that grow in
dry conditions.
 Crassulaceae also known as the stonecrop family or the orpine family
 E.g. Cacti, Crassula argentea, Aeonium, Echeveria, Kalanchoe, and Sedum of
the family Crassulaceae, pineapple (Ananas comosus), orchids, Agave etc.
 Diurenal fluctuation in acid
 Stomata are scotoactive i.e. active during night.
 Stomata are close during day and open at night.
 Acidification during night and deacidification during day.
 Both C3 and C4 cycle are involved.

48. CAM Pathway

49. Overall Photosynthesis Process

50. Significance of Photosynthesis
 Helps to maintain O2 balance in atmosphere
 Provides food to all living organisms.
 Fossile fules
 Plant Products etc