Plant Physiology

1. Plant Physiology
Department of Pharmacognosy
Dr. D. Y. Patil College of Pharmacy, Akurdi,
Pune - 44
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2. Nutrients: The components of food like
carbohydrates, fats, proteins vitamins & minerals.
Nutrients help living organisms :-
i) To build their bodies.
ii) To grow.
iii) To repair the damaged parts of their bodies.
iv) To provide energy to carry out life processes.
Nutrition: The mode of taking food by an
organism and its utilization in the body.
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3. Modes of nutrition
1. Autotrophic nutrition
2. Heterotrophic nutrition
3. Saprophytic nutrition
4. Parasitic nutrition
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4. i) Autotrophic nutrition
- Self nourishing
- is nutrition in which organisms can prepare their own
food & such organisms are called as autotrophs.
- Greek word, ‘Autos’ – self, ‘troph’ – nutrition
- Plants synthesize food by “photosynthesis”
- Non-green bacteria like sulphur bacteria synthesize
food by “chemosynthesis”.
- Chlorophyll present in the chloroplast.
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5. ii) Heterotrophic nutrition
- Ready made food / consumers
- is nutrition in which organisms get their food directly or
indirectly from plants & such organisms are called as
heterotrophs.
- ‘Heteros’ – other, ‘troph’ – nutrition
- Chlorophyll is lacking
- Classified into –
1) Parasites
2) Saprophytes
3) Symbionts
4) Carnivorous plant 5

6. - are plants which do not have chlorophyll and cannot
prepare their own food. They get their food from other
plants.
- Such plants are called as “parasitic” & the plants on
which they climb are called as “host”.
- Eg :- Cuscuta ( Amarbel)
1) Parasitic plants
http://upload.wikimedia.org/wikipedia/commons/1/12/Cuscuta_parasite_plant.JPG 6

7. - Greek word, ‘Sapro’ – rotten, ‘phyto’ - plant
- are plants which do not have chlorophyll and cannot
prepare their own food.
- They get their food from dead and decaying organic
matter. Eg :- mushroom, bread mould etc. They produce
digestive juice on the dead and decaying organic matter
and convert it into a solution and then absorb the
nutrients from the solution.
2) Saprophytes
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8. http://images.wisegeek.com/white-mushrooms-growing-out-of-
moss.jpg
http://www.abdn.ac.uk/rhynie/images/plants/fungi/fungi10.jpg
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9. - Two organisms live in close association and sharing
shelter and nutrients for the mutual benefit to each other
are called as ‘Symbionts’.
- This relationship is called ‘symbiotic relationship’ and
the condition is called ‘symbiosis’.
- Eg :- Lichens,
- Rhizobium bacteria in soil (Leguminous plants)
3) Symbionts
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10. In lichens, an alga and a fungus live together. The
fungus provides shelter, water and minerals to the alga.
The alga provides food to the fungus which it prepares
by photosynthesis.
http://www.bennett-smith.com/Havenfield%20Lichens%203.jpghttp://upload.wikimedia.org/wikipedia/en/9/9d/Plants_flowers_ice_rocks_
lichens_209.jpg
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11. - These plants capture lower animals like insects
- They digest the insect & absorb nitrogenous (protein)
products from its body.
- As they are green they can manufacture their own
carbohydrate food, they depend on insect for proteinous
material.
Insectivorous plants :- are plants which feed on
insects.
Eg:- Pitcher plant.
4) Carnivorous plant
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12. The leaf of the pitcher plant is modified into a pitcher.
The end of the pitcher has a lid which can open & close.
When an insect enters the pitcher, the lid closes & insect
is then digested by digestive juices inside the pitcher.
http://www.carnivorous--plants.com/graphics/pitcher-plant.jpg
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13. http://upload.wikimedia.org/wikipedia/commons/2/20/Darlingtonia
_californica_ne1.JPG
http://upload.wikimedia.org/wikipedia/commons/3/37/Venus_Flytrap_sho
wing_trigger_hairs.jpg
http://upload.wikimedia.org/wikipedia/commons/0/0f/Drosera_cap
ensis_bend.JPG
http://coloradocarnivorousplantsociety.com/2006-10-
13_VFT_vs_Black_Widow_045_crop.jpg
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14. Photosynthesis – Process of food production by plants in
the presence of water, minerals & sunlight.
Chemosynthesis – Non-green bacteria can use energy
which they derive from chemical reaction occurring in
them, with this energy they manufacture their food, this
process is called as chemosynthesis.
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15. Photosynthesis
- Photosynthesis term coined by Barnes in 1898.
- Greek word, ‘photo’ – light, ‘synthesis’ – putting together/
building up
- Process occurs in leaves
- Water & minerals present in soil is absorbed by root and
transported to leaves.
- Carbon dioxide from air is taken up by stomata
- Energy of sunlight is captured by chlorophyll present in
leaves.
- Photosynthesis equation is represented as,
6CO2+12H2O C6H12O6 + 6H2O + 6O2 15

16. Sunlight
Carbon dioxide + Water Carbohydrate + Oxygen
Chlorophyll
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17. Significance of photosynthesis
1. CO2 + H2O + Light energetic organic compound
2. Converts light energy into chemical energy
3. It gives energy in the form of fossil fuels like coal,
petrol, natural gas.
4. Prepares oxygen – essential for all living organisms.
5. Oxygen obtained helps in ozone formation.
6. Helps in production of different primary and
secondary metabolites.
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18. Site of photosynthesis
- Photosynthesis takes place in the green parts of the
plant, mostly leaves & to a lesser extent in young stem,
sepals, skin of developing fruits.
- In leaf specialised cells are present called mesophyll
cells. They are rich in chloroplasts.
- In blue green algae & some bacteria chloroplasts are
absent. They possess lamellae or thylakoids which are
hollow membranes with photosynthetic pigments.
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19. Chloroplast
 Structure: stacked
sacs (thylakoids) that
contain chlorophyll
surrounded by a
double membrane
 Function:
photosynthesis
(conversion of light
energy to chemical
energy stored in the
bonds of glucose)
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20. Where does photosynthesis take
place?
 Chloroplast: site for photosynthesis
 Contains chlorophyll: pigment that activates
photosynthesis & gives plants their green
color
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21. Important parts of the
choloroplast
Thykloids: site of Light rxns. Grana: a bunch of thykloids
Stroma: site of Dark rxns. 21

22. Pathways involved in photosynthesis
- Photosynthesis is involving oxidation – reduction process
by which hydrogen is transferred from water to carbon
dioxide through a ‘carrier’ substance.
- In this process volume of CO2 absorbed is almost equal to
volume of O2 liberated in most green plants.
It involves 2 phases:
1. Light reaction / Photochemical phase
2. Dark reaction / Biochemical / Thermochemical /
Synthetic phase
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23. Light Reactions  needs the sun and water
Dark Reaction  no light needed
Stages of Photosynthesis
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24. Light reaction / Photochemical phase
- Takes place in lamella region in granum
- Two types of photosystems are found in the granum:
i) Photosystem I (PS I) – less accessory pigments &
more chlorophyll a
ii) Photosystem II (PS II) – more accessory pigments
& less chlorophyll a
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- Absorption of light energy by photosynthetic pigments
converts radiant energy into chemical energy
(formation of ATP at the phosphate bond); photolysis
(ionization) of water, formation of reducing agent
(NADP-H2), evolution of molecular oxygen (from
water).
- This reaction involves pigments, solar energy and water
that produce ATP & NADPH2 & are called “Light
reactions”

26. Photon
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PS II Chlorophyll takes photon
& undergoes resonance
Excites PS II
Releases 4 electrons (e-)
4 e- combines with 4 protons
Plastoquinone Qb(4e-+4P)
e- transported to Cytochrome b6f
e- transported to Plastocyanin
PS I
Ferredoxin
Ferredoxin NADP reductase (FNR)
ATP synthase
ATP
2H2O
O2 & H+
Binds to
2 P released in lumen
NADP+ + 4e- + 2H+
NADPH
ADP + Pi
Light reaction

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Overview of light reaction
1. Needs sunlight
2. Takes place in thylakoid
3. Sunlight splits H2O to produce H+ (for energy) and O2
(waste).
4. The end products are NADPH and ATP, which are both
energy sources that drive the dark reactions.
5. ATP – energy donor for synthesis of carbohydrates from
CO2.
6. NADPH2 – acts as reducing power and is utilized in
reduction of CO2 to carbohydrates during dark
reactions.

28. - Light is not required
- Takes place in the stroma
- Given the name CARBON FIXATION (Calvin
Benson Cycle) because it will now fix carbon
dioxide chemically to form glucose
Dark Reaction
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Calvin Cycle
1. Carboxylation Phase 2. Reduction Phase
2 moles of 1, 3 diphosphoglyceric acid
2PGA
Ribulose 1, 5- diphosphate
(RuDP / RuBP)
6 – carbon unstable
compound
2 moles of Phosphoglyceric
acid (PGA)
Atmospheric CO2
Phosphoglyceraldehyde (PGAL) + Pi + NADP
Isomer - dihydroxy acetone phosphate
(DHAP)
RuDP crboxylaseAccepted
RuDP crboxylaseHydrolysis
12 ADP
12 ATP
PGA Kinase
12 NADPH2
12 NADP
Glyceraldehyde 3-phosphate dehydrogenase
Triose – phosphate isomerise
i) Synthesis Phase
ii) Regeneration Phase

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i) Synthetic phase
- For synthesis of 1 glucose molecule, 6 turns of Calvin
cycle is required i. e. 6CO2 + RuDP
- PGAL + DHAP
Fructose – 6-phosphate
Glucose – 6-phosphate
Glucose
Dephosphorylation & Pi
Isomerised
Dephosphorylation
Fructose 1, 6-diphosphate

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ii) Regeneration Phase
PGAL + DHAP
Fructose 1, 6- biphosphate
Fructose 6- phosphate
Ribose – 5 –phosphate + Erythrose – 4- phosphate
Sedoheptulose 1, 7 - biphosphate
Sedoheptulose 7 - phosphate
Ribose 5- phosphate + Xylulose – 5- phosphate
Ribulose 5- phosphate
RuBP + CO2 PGA
Dephosphorylation
PGAL
DHAP
Dephosphorylation
DHAP
RuBP
6ADP 6ATP
2ATP + 2NADPH2

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Dark Reaction
1. Sunlight is not required
2. It takes place outside the thylakoid
3. Use the energy produced during light reactions
4. CO2 is fixed from the air & converted into starches
and sugars using NADPH and ATP to help in the
conversion.
5. ADP, Pi and NADP get regenerated & are required for
the synthesis of ATP and NADPH2 during the light
reaction.

33. Overall Chemical Equation
 6 CO2 +12 H2O+ LIGHTC6 H12 O6+6 O2 + 6H2O
 REVERSE OF CELL RESPIRATION
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34. What is chemosynthesis?
Chemosynthesis is used when sunlight is not
available.
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What happens during chemosynthesis?
During chemosynthesis, organisms use inorganic
substances in place of sunlight to make sugar and
oxygen.
What is the equation for chemosynthesis?
Inorganic substances + water+
carbon dioxide
Oxygen + sugar

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Which organisms undergo
chemosynthesis?
Organisms that do
not receive sunlight
have to do
chemosynthesis in
order to make food
for themselves
(bacteria or deep
water organisms).

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Why does chemosynthesis happen?
Some ocean organisms
live so far below the
surface that they do not
get any sunlight.
They use chemosynthesis
instead of photosynthesis.

37. Chemosynthetic organisms
- Organisms using chemical energy for the synthesis
of carbon compounds are called Chemosynthetic
organisms.
- They are of 2 types:
i) Chemosynthetic autotrophs
ii) Chemosynthetic heterotrophs
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38. i) Chemosynthetic autotrophs
- These bacteria are aerobic & the energy required for
the metabolic processes is derived from the oxidation of
certain inorganic compounds present in their
environment.
- The energy released by this oxidative process is used to
convert CO2 to carbohydrate through several
intermediate reaction. Other organic compounds are
also formed along with carbohydrates.
- Oxygen is not liberated during this process.
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39. Examples of chemosynthetic autotrophs are:
a) Nitrosomonas – It oxidizes ammonia into nitrite,
energy liberated during this process is used for
photosynthesis of carbohydrates.
2NH3 + 3O2 2NO2
- + 2H2O + 2H+ + Energy
b) Beggiatoa is a sulphur bacteria & grows in springs &
stagnant water containing hydrogen sulphide. Oxidises
H2S to sulphur and water. Energy liberated is used for it’s
growth and sulphur is stored as granules inside the cell.
H2S + [O] H2O + S + Energy
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40. c) Iron bacteria:
- They are filamentous cells.
- Grows in lakes & marshes (water containing ferrous
iron)
- They obtain energy for synthesis of organic
compound by oxidation of ferrous hydroxide to ferric
hydroxide(water is often reddish due to this activity).
40http://2009.igem.org/Team:Tokyo_Tech/Iron-oxidizing_bacteria

41. ii) Chemosynthetic heterotrophs
- Fungi, most bacteria, animals and man.
- As they cannot prepare their food materials they obtain
energy for growth by chemical reactions such as
oxidising the organic compounds.
- Energy released when glucose gets oxidised in the
process of respiration hence the process is
chemosynthetic heterotrophic and organisms are
chemosynthetic heterotrophs.
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http://www.bigelow.org/foodweb/chain4.html