Plant nutrition

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

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As light intensity increases carbon dioxide from respiration is equal to carbon dioxide absorbed for photosynthesis

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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

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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