Physiological Processes Affecting Crop Production

Flashcards about Physiological Processes Affecting Crop Production. Topics include photosynthesis, light and dark reactions, and factors affecting photosynthesis.

Physiological Processes in Crop Production

Growth and development of crops result from the interaction of various physiological processes, namely: Photosynthesis, Respiration, Transpiration, Translocation.

Photosynthesis

A chemical reaction where plants and plant-like organisms (algae) make their energy (glucose) from sunlight.

Importance of Photosynthesis

Makes organic molecules (glucose) out of inorganic materials (carbon dioxide and water); begins all food chains/webs; makes oxygen gas.

Requirements for Photosynthesis

Water, carbon dioxide, light, and chlorophyll.

Process of Photosynthesis

Plants use sunlight to turn water and carbon dioxide into glucose, which they use as food for energy and as a building block for growing.

"Putting together with light"

Photo-synthesis definition.

Anoxygenic Photosynthesis

Phototrophic process of obligate anaerobes, where light energy is captured and converted to ATP, without the production of oxygen; water is not used as an electron donor.

Oxygenic Photosynthesis

The most common type of photosynthesis, seen in plants, algae, and cyanobacteria, where water is the initial electron donor and molecular oxygen is freed as a byproduct.

Chlorophyll

The green pigment in plants which captures, transforms, translocates, and stores energy for all forms of life.

Photosynthesis

Converts light energy into chemical energy.

Leaf

The chief site of photosynthesis in plants.

Structural Parts of a Leaf

Upper and lower epidermis (stomates), mesophyll cells (chlorophyll), and vascular bundles (transport).

Types of Mesophyll

Palisade parenchyma (regular shaped palisade cells) and spongy parenchyma (irregular shaped).

Stoma

The opening through which plants exchange gases.

Chloroplasts

The tiny green structures within cells where photosynthesis happens.

Glucose

Provides the energy and carbon needed to make other plant materials like wax and proteins.

Carotenoids

Absorb light in regions of the spectrum not absorbed by chlorophylls and transfer that energy to chlorophyll.

Chlorophyll

The principal pigment involved in photosynthesis; absorbs light maximally in the violet blue and red regions of the visible spectrum and reflects green light.

Kinds of Chlorophyll

chlorophyll a (bluish green) and chlorophyll b (yellowish green).

Reaction center and the harvesting center pigments.

Packed into functional clusters called photosystems.

Photosystem I (PSI)

Chlorophyll–a with maximum absorption at 700 nm.

Photosystem II (PSII)

Chlorophyll–a with peak absorption at 680 nm.

Primary Electron Acceptor for Photosystem I

Iron protein (Fe-S-protein).

Primary Electron Acceptor for Photosystem II

PHEOPHYTIN

The Entire Process of Photosynthesis

Takes place inside the chloroplast and involves light reactions and dark reactions.

Light Reactions

Take place in the grana of the chloroplasts where chlorophyll can be found located on the membranes.

Dark Reactions

Take place at the stroma of the chloroplasts where it is absent from chlorophyll.

Light Reaction

Occurs in the chloroplast of the mesophyll cells of the leaves; generates organic molecules such as ATP and NADPH needed for dark reactions.

First Step of Light Reaction

Chlorophyll absorbs the red and blue segment of the white light.

Second Step of Light Reaction

The chlorophyll pigments which are excited give up their electrons and to compensate for the loss of electrons, water is split to release four hydrogen ions and four electrons and oxygen.

End products of light reaction

ATP and NADPH.

Photophosphorylation

The synthesis of ATP by the light - induced phosphorylation of ADP.

Non-Cyclic Photophosphorylation

Both PSI and PSII are functional; water is the primary source of electrons and H+ and gets photolysed; NADP is the final acceptor.

Cyclic Photophosphorylation

Only PSI is functional; electron comes from and returns to the same chlorophyll P700 molecule.

Dark Reaction

Occurs in the stroma; inorganic carbon is converted to carbon; CO2 is reduced and carbohydrates are produced.

Three Pathways of Carbon Dioxide Fixation

Calvin Benson Cycle/ Reductive Pentose Pathway, C4 or Hatch Slack Pathway, and CAM or Crassulacean Acid Metabolism Pathway.

Calvin Benson Cycle/ Reductive Pentose Pathway

Fixation and reduction of one molecule of CO2 requires three molecules of ATP and 2 NADPH; CO2 acceptor is RUBP; the first stable product is 3-PGA.

C4 or Hatch Slack Pathway

First product is 4-C oxaloacetic acid; presence of Kranz anatomy.

CAM or Crassulacean Acid Metabolism Pathway

Operates in orchids, pineapple, other succulent plants wherein stomates are closed during the day and open during the night.

Categories of Factors Affecting Photosynthesis

Internal and External (environmental) factors.

Internal Factors: Chlorophyll

Amount of chlorophyll present.

Internal Factors: Leaf Age

Leaf age and anatomy.

Internal Factors: Demand for Photosynthate

Rapidly growing plants show increased rate of photosynthesis in comparison to mature plants.

External Factors Affecting Photosynthesis

Temperature, light, carbon dioxide, water, and mineral elements.

External Factors: Light

The rate of photosynthesis increases with increase of intensity of light within physiological limits.

External Factors: Temperature

Very high and very low temperature affect the rate of photosynthesis adversely.

External Factors: Carbon Dioxide

Since carbon dioxide is one of the raw materials for photosynthesis, its concentration affects the rate of photosynthesis markedly.

External Factors: Water

Loss of water in the soil is immediately felt by the leaves, which get wilted and their stomata close down thus hampering the absorption of CO2 from the atmosphere.

External Factors: Mineral Elements

Some mineral elements like magnesium, copper, manganese and chloride ions, which are components of photosynthetic enzymes, and magnesium as a component of chlorophylls are important.