Plant Life Processes, Plant Growth and Development, Photosynthesis, C3 Pathways, C4 Pathways, CAM Pathways

1. Jupite Mark U. Banayag, L.Agr
Faculty
Compostela Valley State College
Purok 10, Poblacion, Compostela, 8803 Compostela Valley
pitebanayag@gmail.com
PLANT LIFE PROCESSES

3. Concepts of Growth and
Development
•Plant Development vs. Plant
Growth vs. Differentiation
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4. Growth
•Growth-
•irreversible change in size and weight,
mass, and/or volume of a plant or its
parts.
•various ways of quantifying plant growth.
These include cell number, fresh weight,
dry weight, plant height, length, width,
area, and volume.
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5. Types of Growth
•Primary Growth
• The mitotic division of meristematic cells present at
the root and shoot apex increases the length of the
plant body.
•Secondary Growth
• The secondary meristem increases the diameter of
the plant body.
•Unlimited/ Indeterminate Growth
• The root and the shoot system of plants grow
continuously from germination stage to the death or
throughout the life span of the plant.
•Limited/ Determinate Growth-
• The leaves, fruits and flowers stop growing after
attaining certain size. JMUBanayag

6. Differentiation
•Differentiation
•involves a series of qualitative changes
occurring in plants. It is an orderly process of
change in which structurally simple and
genetically identical cells become different by
becoming specialized for certain functions and
produce the various tissues and organs of a
plant. The shift into specialized cells occurs due
to differential activation of a cell’s genome
(Moore et al. 2003).
•Tissue culture
•Leaves to Flower JMUBanayag

7. Development
•Development-
•Refers to the sum of all changes
that an organism goes through in its
life cycle, including growth and
differentiation.
•seed germination to seedling stage,
vegetative growth, maturation,
flowering, fruit and seed formation,
and senescence
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8. Growth Curve
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9. Kinetics of Growth
•The growth (size) of many plants, when
plotted as a function of time will give an
S-shaped (sigmoid) curve.
•The growth curve has 3 distinguishable
phases:
• lag phase
•log (exponential) phase
•senescence phase
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10. Sigmoid Pattern

11. Phases of Plant Growth
1. Lag Phase-
• period in which internal changes occur
preparatory to growth
• early germination and vegetative growth
2. Log or Exponential Phase-
• the fastest rate of growth
• middle and last stage of vegetative growth
• ”grand Period of Growth”
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12. Phases of Plant Growth
3. Declining phase-
• plants have fully developed number and size
of leaves
•onset of flowering
•The increase in growth due to flower
formation is offset by leaf abscission
4. Steady Phase
• rate of growth is steady
• Pod or grain filling to ripening and maturity
until growth ceases.
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13. Phases of Plant Growth
5. Senescence
• Plants begin to die and abscission of
the leaves set in
• Some plant parts fall down
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14. Measurements of Growth
•Cell number,
•Increase in fresh weight,
•Increase in dry weight,
•Plant height,
•Length,
•Width,
•Volume,
•Surface area
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15. Stages of Plant Growth and
Development
•Vegetative and Reproductive Stages
•Vegetative stage has 3 sequential phases
• Juvenile Stage
• Transition Phase
• Adult Phase
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16. Vegetative stage- 3 Sequential
Phases
• Juvenile Stage – germination period, seedling growth
and up to a point of growth when transition phase
begins.
• length of juvenility period varies with some factors
such as the environment and genetic make-up of the
plant
• Transition Phase – the plant is gradually losing its
juvenile characteristics and at the same time gradually
acquiring the adult characteristics
• Adult Phase – the plant is already very capable of
flowering, i.e. can readily respond to flowering stimuli.
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17. Reproductive Stage
• Mainly concerned with the production of reproductive
structures
• Self-inducing Plants – the floral morphogenesis is entirely
determined endogenously
• may flower as soon as the genetically determined age for flowering is
reached.
• may flower when the vegetative parts have reached a certain size.
• may flower when their carbon-protein balance is favourable
• Non-self-inducing Plants – flowering is dependent upon
certain environmental factors such as temperature and
photoperiod.
• These type of plants must first be in the “ripeness-to-flower” status
before they can respond to flowering stimuli.
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18. Plant Life Processes
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19. Photosynthesis vs Respiration
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20. Photosynthesis
•Yield of crops ultimately depends on the size
and efficiency of their photosynthetic system.
(the basis of crop production)
•Solar energy that a plant stores in
carbohydrates during photosynthesis is used to
run and maintain process in the plants.
• Such as: absorption of water and nutrients,
transporting them to leaves, and converting other
products of photosynthesis to cell walls and other
cellular parts; so that the plant can grow and
develop.
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21. The most important process on earth … It is the
connecting link between solar energy and life
RESULTS OF PHOTOSYNTHESIS
1. Conversion of light energy to chemical energy for all
plant metabolic processes
2. Conversion of inorganic compounds into essential
foodstuffs and other useful products
3. Release of oxygen into the atmosphere which is used
for respiration by plants and animals

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23. Respiration
• For the carbohydrates to be utilized, their energy
must be released in the process of respiration.
• The released energy can be:
• stored as chemical energy
• used as mechanical energy
• stored as electrical energy
• released as heat
• Overall reaction of respiration is the breakdown of
carbohydrates into CO2 and water
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24. Pathways of Glucose Oxidation
• Glycolysis (glucose is oxidized to pyruvic acid)
• TCA (Kreb cycle) – p. acid is completely degraded to
water and CO2, NAD is produced
• Pentose Phophate pathway; NADP is produced
• Oxidation Pathways of Fats and Oils
• B-oxidation – removes 2 carbon atoms from a fatty acid at a time in
form of acetyl CoA
• L-oxidation – removes 1 carbon atom at a time
• Glyoxylate cycle – conversion of fatty acid to sucrose Acetyl CoA
produced during the B-oxidation of fatty acid is converted to
oxaloacetate, and by reverse glycolysis, OAA will be converted to
sucrose
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25. Parts of Plant
The ultimate growth
of plant in terms of
dry weight often
termed as net
photosynthesis.
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27. Photosynthesis and Respiration
•The ultimate growth of plant in terms of dry
weight often termed as net photosynthesis.
NP= TP-R
Where: TP= total photosynthesis
R= Respiration
NP= net photosynthesis
Given total photosynthesis, the greater the deference
between total photosynthesis and respiration, the faster
the growth of the plant.
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28. Photosynthesis and Respiration
•Sometimes the difference is zero which
means that there is no growth since the
amount of produced photosynthesis is all
broken down during respiration.
•The level of light at which net
photosynthesis is zero is called light
compensation point.
•Photosynthesis and respiration are the
processes on which all the other
metabolic processes directly or indirectly
depend, hence are the most important.
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30. The Structures Involved in Photosynthesis

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33. Stomata
•A very important feature of leaves as
a photosynthesizing organ is the
presence on their surfaces of a large
number of tiny openings.
•CO2 entry point and O2 exit point.
•Ex. Cabbage-
•14,100 stomates/sq.cm- upper surface
•22,600 stomates/sq.cm- lower surface
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35. • Xylem vessels- Conduct
water from the roots to the
leaves
• Phloem vessels- Distribute
food materials from the
leaves.JMUBanayag

36. The Light Requirement...
•Only the visible (white) light of the
electromagnetic spectrum drives the
photosynthetic process
•From violet (400nm) to red (700nm)
•Light striking a surface can be reflected,
transmitted or absorbed
•Photosynthesis utilizes 1-10% solar radiation
absorbed by crop surfaces during daytime
•Light absorption is made possible through
pigment molecules
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39. Site of Photosynthesis
•Photosynthesis occurs in the chloroplast of the
cells where the pigment chlorophyll and
sometimes other pigments like carotenoids are
found.
•Chlorophyll gives leaves their green color.
•Carotenoids are orange or yellow pigments.
•Photosynthesis thus occurs in green parts of
the plant: leaves, and to some extent, in stems
and green fruits.
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40. Steps in Photosynthesis
•2 phases of
photosynthesis
•Light reaction
•Dark reaction
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41. Simple representation-
Leaves serves as Factory
•Enzymes are the worker of the factory
•Chlorophyll is the machinery
•The factory has to sections.
• In the first section, of the factory, the sun
provides the energy. Water is fed into the
factory from the roots. It is chopped up into its
smaller pieces(hydrogen and Oxygen) and in
the process also form ‘batteries’ (ATP) to
provide power to run the second section of the
factory.

42. Simple representation- Leaves
serves as Factory

43. Light Reaction
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44. Dark Reaction
•Stage of the Dark Reaction:
•assimilation of CO2, production of CH2O
•use of ATP and NADP-H2 in the process
•consists of a series of reactions
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45. C3 vs C4 vs CAM
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46. Calvin cycle or C3 Pathway
•also called the photosynthetic carbon reduction
(PCR) cycle
•Melvin Calvin, an American biochemist
•First stable product is three-carbon 3-
phosphoglycerate (3-PGA) and operates in
most crop plants
•Steps:
1. Carboxylation – addition of water
and carbon dioxide to RuBP, RUBISCO is
the enzyme involved
2. Reduction of 3-PGA to 3-phosphoglyceraldehyde
3. Regeneration of RuBP
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48. Step 1: CO2 Fixation
• CO2 that diffuses into the stroma of the chloroplast in
mesophyll cells is added (covalently bonded) to the five-
carbon acceptor ribulose-1,5-bisphosphate (RuBP,
C5H12O11P2) also called ribulose-1,5-diphosphate (RuDP),
yielding a six-carbon intermediate product.
• This intermediate is hydrated and then cleaved, producing
two molecules of three-carbon 3-phosphoglycerate or
phosphoglyceric acid (3-PGA or simply PGA, C3H5O6P).
• The reaction is catalyzed by the enzyme ribulose-1,5-
bisphosphate carboxylase/oxygenase (RuBisCo).
Rubisco
CO2 + RuBP ----------------------------------> 2 3-PGA
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49. Step 2: Carbon Reduction
• Each of the two molecules of 3-PGA undergoes further
reactions to produce the three-carbon triose phosphate
sugar- glyceraldehyde-3-phosphate (G3P, C3H7O6P),
also called phosphoglyceraldehyde (PGAL).
• A molecule of G3P is first phosphorylated by ATP,
producing 1,3-bisphosphoglycerate which is in turn
reduced to G3P with NADPH as the reducing agent.
• Glyceraldehyde-3-phosphate or G3P is the
carbohydrate product of the C3 cycle and is the
precursor of glucose and other products of metabolism.
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50. Stage 3: Regeneration stage
• Some molecules of G3P go through further reactions
which result to the reformation of RuBP, the CO2
acceptor in the C3 cycle.
• To complete the process of photosynthesis, the other
molecules of G3P leave the cycle and proceed to a
series of reactions to form glucose and other sugars,
starch, and other organic compounds.
• It takes six turns of the cycle, or a total of six molecules
of CO2, to produce one molecule of glucose (C6H12O6)
(Mathews and Van Holde 1990; Simpson 2010).
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54. Hatch and Slack or C4 Pathway
•Photosynthesis occurs in two adjoining types of
cells, the mesophyll and bundle sheath cells in
plant species called C4 plants
•Both C3 and C4 cycles operate in the non-light-
requiring or Dark Reactions of photosynthesis
but spatially, that is, in different cells: C4 in
the mesophyll cells immediately followed by
C3 cycle in the bundle sheath cells.
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Diagram of Kranz
Anatomy

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57. Hatch and Slack or C4 Pathway
•Product is 4-C oxaloaceticacid before
proceeding to the Calvin cycle
•Steps:
1. Carboxylation of PEP to OAA, PEP
carboxylaseis enzyme involved
2. reduction of OAA to malate
3. Decarboxylation of malate in the bundle sheath
cells to form pyruvic acid
4. transfer of pyruvicacid to the mesophyllcell
5. fixation of carbon dioxide to form 3-PGA
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58. Step 1: Carboxylation of PEP to OA
• CO2 first enters the leaf and into the mesophyll cell.
• It is then hydrated to produce bicarbonate ion (HCO3-) in
the cytoplasm with carbonic anhydrase (CA) as catalyst.
• Followed by carboxylation reaction utilizing HCO3- instead of
CO2 as the inorganic carbon substrate.
Hydration of CO2 (catalyzing enzyme is carbonic anhydrase):
CO2 + H2O ------------> H2CO3 ----------> HCO3- + H+
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59. Step 1: Carboxylation of PEP to OA
• HCO3- reacts with the three-carbon acid
phosphoenolpyruvate (PEP or PEPA, C3H5O6P) to
form oxaloacetate (OAA, oxaloacetic acid= C4H4O5).
• The reaction is catalyzed by the carboxylating enzyme
phosphoenolpyruvate carboxylase (PEPcase, PEPC or
PEPCO).
• OAA is a four-carbon product, hence the term C4
photosynthesis.
Carboxylation of HCO3- (catalyzing enzyme is PEPcase)
HCO3- + PEP ---------->OAA
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60. Step 1: Carboxylation of PEP to OA
• Summary reaction is commonly written as:
PEPcase
CO2 + PEP --------------------------------------> OAA
• The hydration reactions leading to the formation of
HCO3- and its carboxylation are skipped
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61. Step 2: Reduction of OAA to Malate
•OAA is then reduced to malate (malic acid=
C4H6O5) and transported to the adjacent
bundle-sheath cells.
•Malate is utilized in two ways:
• for the regeneration of PEP, and
• for the supply of CO2 for the succeeding C3 cycle.
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62. Step 4: Transfer of pyruvicacid
• Malate is decarboxylated in which CO2 is removed
and pyruvate (pyruvic acid= C3H4O3) is formed.
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Step 3: Decarboxylation of Malate
• Pyruvate goes back to the mesophyll cell where it is
phosphorylated to PEP, the CO2 acceptor in the C4
cycle.
• The freed CO2 enters the C3 cycle within the bundle
sheath cell.

63. Step 5: Fixation of carbon dioxide to
form 3-PGA
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64. JMUBanayag
The C4 Photosynthetic pathway
(adopted from Taiz and Zeiger, 2004)

65. Some examples of C4 Vegetables
• amaranth, sweet corn and Malabar spinach.

66. Crassulacean Acid Metabolism
Pathway (CAM)
•Operates in orchids, pineapple, other
succulent plants wherein stomates are
closed during the day and open during the
night.
• They open their stomates at night to absorb
CO2, and close them during the day to
reduce transpiration
• They fix CO2 into 4-carbon acids,
oxaloacetate, using PEP CARBOXYLASE,
at night when stomates are open.
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67. Crassulacean Acid Metabolism
Pathway (CAM)
• the 4-carbon acid (malate) formed is temporarily
stored in the vacuole at night.
•During the day, malate returns to the chloroplast
where it is decarboxylated and the CO2 moves
into the C3 cycle while PEP is released
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Remember : CO2 fixation occurs at night because the
stomates are close during the day
the first compound formed is oxaloacetate
(4-carbon compound)

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CO2 fixation pathway in CAM plants

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The CAM Photosynthetic pathway (adopted from Taiz and Zeiger, 2002)

70. Summary among Pathways
C3 (Calvin cycle) C4 (Dicarboxylic acid) Crassulaccan (CAM)
Kranz Anatomy none Present None
CO2 acceptor RuBP PEP PEP
CO2 fixation product 3-PGA OAA (C4 acids) OAA (C4 acids)
Carboxylase
RuBP
carboxylase
PEP carboxylase PEP carboxylase
CO2 fixation
light light Darkening C4 cycle
Light C3 cycle
Photorespiration High Low Very low
CO2 comp. Pt. High Low low
Energy reqt. 3 ATP 5 ATP
Per CO2 fixed 2 NADPH2 2 NADPH2
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Simplified summary of photosynthesis

73. Types of Photosynthetic Patterns
•First stable compound formed before glucose is
finally formed is a three-carbon acid, phosphoric
acid.
Plants exhibiting this pattern of photosynthesis is
called C3 plants
Most crops are C3 plants
• Four-carbon acid as the first stable product of
photosynthesis are called C4 plants.
• Generally originated from hot or dry areas, sandy or
salty soils, conditions usually unfavorable for the
normal growth of plants.
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76. Photorespiration
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Chloroplast or Mitochondria

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79. Photorespiration
• Only in C3 plants ; very minimal or zero in C4 plants
• Utilizes the enzyme RUBISCO
(ribulose biphosphate carboxylase/ oxygenase)
• Fixes oxygen instead of CO2 … when O2
concentration in the plant is higher
• Since RUBISCO is both a carboxylase and an
oxygenase, the O2 and CO2 compete for the same
enzyme and for the same substrate, RuBP
• Results in CO2 loss in photosynthetic tissues… and is
the major source of CO2 evolution in the light by C3
plants
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80. Photorespiration
•Ribulose-1,5-bisphosphate (RuBP), the CO2
acceptor in the Calvin cycle, will be lost;
•The fixation of CO2 via the C3 pathway is
stopped; and
•Instead CO2 that is already fixed is released.
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83. Requirements of Photosynthesis
•Light
•Leaves
•Carbon dioxide
•Water
•Enzymes
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84. Light
•In general, the greater the intensity and
duration of sunlight, the more chance there is
for the leaves to capture sufficient amount of
light energy.
•There is a point, however, when the amount of
light (light intensity ) is too high that the leaf can
no longer use all the energy from the sunlight.
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85. Intercropping- cropping increases the
efficiency of using light energy per unit of
ground area.
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86. Properly spaced plants: light is being used by
the leaves instead of being wasted on the
bare soil
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87. Leaves
•While sunlight is available, the plants must
have leaves to capture the sun’s energy or it
will be lost.
•The greater the leaf area, the better the
photosynthetic rate
•Theoretically, the larger the leaves and the
greater the number, the bigger photosynthetic
rate. However, the arrangement of the leaf also
has much to do with photo synthetic rate.
•Arrangement and potential size of leaves are
determined by the species and variety.
(F1 corn with erect leaves)
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88. Leaves
Erect Dropping
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89. Carbon Dioxide
•Atmosphere contains 0.03% of CO2.
•The amount can be increased to enhance
photosynthesis, provided other conditions
are optimum
•Possible only inside a greenhouse or
polyethylene film chamber
•Increasing CO2 to 0.1% can double the
photosynthetic rate of some crops.
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91. CO2 Generator for greenhousesJMUBanayag

92. Enzymes
•Although photosynthesis appears to be a
simple reaction, it is actually composed of
many chemical reactions, each being triggered
and speeded up by an enzyme.
•For enzymes to be manufactured and to
function, some nutrients have to be presented
in adequate amounts: Carbon, hydrogen,
oxygen, nitrogen, phosphorus, potassium,
calcium, and other essential elements.
•Each enzyme has its own nutrient requirements
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93. Respiration
•Takes place in the mitochondria of cells.
•Composed of many reactions which are all
activated by enzymes.
•Respiration increases rapidly with the increase
in temperature.
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95. Translocation
•Water and nutrients absorbed by the roots must
be brought to the leaves and other parts of the
plants for photosynthesis to occur. Likewise,
food from the leaves must be distributed
throughout the plant.
•The movement of these dissolved substance is
called translocation.
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96. • Xylem vessels- Conduct
water from the roots to the
leaves
• Phloem vessels- Distribute
food materials from the
leaves.

97. Translocation
•Plant parts require more food are:
Growing tips
Buds
Young flowers
Developing fruits or storage roots
•They get as much food as they need at the
expense of the other plant parts and are
termed as sink tissues.
•Fully developed leaves which produce and
thereby supply carbohydrates are referred
to as the source.
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98. •Carbohydrates from a
source go to the nearest
sink.
•Thus, the more leaves
there are above a
developing fruit, the
bigger the fruit will
develop.
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99. • Credits to the owners of slides and contents being used.
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