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Plant Nutrition
B M Subramanya Swamy M.Sc. B.Ed. CIE Co ordinator & Examination Officer
Kanaan Global School Jakarta
Indonesia [email protected]
Plant nutrition
• Introduction
• Photosynthesis
• Leaf structure
• Mineral nutrition
Introduction
• Autotrophs :organisms that can synthesize their organic material from inorganic material in the environment they are called producer
• They include all green plants and some bacteria
• Chemosynthetic Autotrophs utilize chemical energy instead of light energy to synthesize their organic materials
• Heterotrophs they do not make their own food they obtain carbon and energy from organic materials already produced by autotrophs
• They include animals and fungi
• They are called consumers
Photosynthesis
• Maintain 0.03% of carbon di oxide in the air
• When carbon dioxide is trapped in the air there is a global increase in co2 levels
• Green plants help to reduce carbon di oxide in the air during photosynthesis
• Light energy is used by green plants to synthesise organic compounds such as sugars from inorganic compounds like water and carbon di oxide
• Photosynthesis is a process by which light energy from sun is converted into chemical energy. Carbon di oxide and water react using sunlight absorbed by chlorophyll to produce glucose and oxygen
Chlorophyll
• Most abundant photosynthetic pigment in plants
• Located mainly in the chloroplast
• Consists of chlorophyll a & b both absorbs blue and red light
• Chlorophyll a is the primary pigment for photosynthesis
Comparison of light and dark reactionLight reaction Dark reaction
Occurs in chloroplast Occurs in chloroplasts but not chlorophyll
Sunlight activates chlorophyll and activated chlorophyll splits water (photolysis) into hydrogen ions and oxygen and energy
Hydrogen ions combines with oxygen and energy to form glucose
There is a conversion of light energy into chemical energy
The reaction involves enzymes and is temperature dependent
Light reaction cyclic photophosphorylation
LIGHT ABSORBTION AND TRANSFER
TO THE REACTION CENTERS
NADP reductase
2H2O
O2 + 4H+
2H+ + 2NADP
NADPH
4 e-
4 photons
4 photons
2 H+
CYT B6f
PC
PSIPSII
Fd
The Path of Electron and Proton Flow in Photosynthetic Electron Transport
PQ
NADP reductase
2 H+
4 H+
CYT B6f
PC PSIPSII
PQ
Fd
CYCLIC PHOTOPHOSPHORYLATION
Under conditions where NADP+ regeneration is slow, or ATP demand is high, the leaf can cycle electrons between plastoquinone and PSI, and in doin so pump protons across
the membrane. This is termed cyclic photophosphrylation.
PHOTOSYSTEM I
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+ H+H+ H+H+ H+
H+ H+
H+
H+
H+
H+
H+
H+H+ H+
H+
H+ H+
H+
H+ADP+ Pi
ATP
3 H+
Thylakoid Lumen – compartment of low pH
Chloroplast stroma – region of high pH
PHOTOPHOSPHORYLATION
ATP Synthase(F-type ATPase)
Phase 1: Carboxylation
RuBP (5 carbon) + CO2 2 PGA (3 carbon)RUBISCO
Note: The oxygen in CO2 is incorporated into one of the PGA molecules. It is not released as O2.
Properties of Rubisco(Ribulose-1,5-bisphosphate carboxylase/oxygenase)
In primitive photosynthetic bacteria, Rubisco exists as a
dimer of two subunits
In the evolution of the blue-green algae, the primitive, two-
subunit form of Rubisco was modified by the combination of 4 dimers to give a complex of 8 subunits in four pairs of dimers.
RuBP Oxygenation
RuBP (5 carbon) + O2 RUBISCO PGA + PG
Summary of photosynthesis
External view of leaf
Lamina Flat thin broad
Large surface area for absorption of sunlight
Stomata found on the lower surface
Veins Good water supply throughout the leaf
Internal structure of a leaf
Epidermis •Single layer of cells
•Outer wall of cells covered with cutin
•No chloroplast
Cutin •Waxy substance
•Impervious to water and gases
Stomata •Kidney shaped cells
•Only on lower epidermis
Mesophyll palisade cells
•Between upper and lower epidermis
•1-2 layer of closely packed cells
•Large number of chloroplast
Spongy Mesophyll
•Loosely arranged
•Irregular cell
•Large intercellular space
•Facilitates diffusion of gasses
•Has chloroplasts
Vascular tissue •Forms main vein and branch veins of lamina
Xylem •Conducts and distributes water and mineral salts
Phloem •Carries products of photosynthesis to other parts of plant
Vascular bundle •Surrounded by a layer of cells forming the bundle sheath
Chloroplast •Arrangement in palisade cells to absorb maximum amount of sunlight
•More found in palisade cells than in the spongy mesophyll cells
Stomata •Works together with the mesophyll cells for efficient gaseous exchange
•Carbon dioxide enters and oxygen leaves
•Controlled by opening and closing of stomata
Opens (day) •Photosynthesis produces sugar
•This create a concentration gradient causing osmosis of water into the guard cells
•Cells balloon up pores open
Close (night) •Sugar is converted to starch
•Water is lost to neighboring cells
•Guard cells become flaccid pores closes
•This reduces intake of carbon dioxide by leaf
•Photosynthesis reduces and then stops
•Hydrolysis of starch begins
Factor affecting photosynthesis
Carbon dioxide Temperature Light
Carbon dioxide in air is about 0.03% and does not vary much
In the dark stage photosynthesis is enzyme controlled
Increase light intensity increase rate of
photosynthesis
Increase in carbon dioxide increase rate of photosynthesis
Increase temperature to 40 C decrease the rate of photosynthesis as enzyme action is greatly reduced
Up to saturation point
Further increase in light has no effect
Increase only up to carbon dioxide saturation point
Temperature greater than 40 c enzymes are denatured and photosynthesis stops
Absence of light no photosynthesis only
respiration
----------- -----------------------
As light intensity increases carbon dioxide from respiration is equal to carbon dioxide absorbed for photosynthesis
-------- ----------------------
As light intensity increase increases further net releases of carbon dioxide and uptake of carbon dioxide leads to an increase in the amount of sugar in the plant
--------------
------------------------
At very high light intensity photosynthesis slows down as UV damages chlorophyll
Mineral Nutrition
• Macronutrient – chemical elements needed in rather larger amounts
• E.g nitrogen, phosphorous, sulpur, magneium, potassium & calcium
• Micronutrient – traces elements needed in tiny amounts
• E.g. manganese, cobalt, zinc, copper, molybdeum
Element Function Deficiency symptom
Nitrogen Component of chlorophyll amino acids & protien
Stunted growthChlorosis of leaves
Phosphorous For release of energy Stunted growth Dull green leaves Leaves with curly brown edges
Sulphur Component of protein and aminoacids
Chlorosis of leaves Weak stem
Magnesium Component of chlorophyll Chlorosis of leaves Death of leaf or portion of it
Potassium For increase hardness Chlorosis of leavesDead tissue tips and edges of leaves
Calcium Cells formation at root and shoot tips
Stunted growthPoor budsNew leaves distorted in shape