Recap.

Textbook Chapter 7

Nutrition in PlantsLearning outcomesidentify the cellular and tissue structure of a dicotyledonous leaf, as seen in cross-section under the microscope and state their functions:distribution of chloroplasts photosynthesisstomata and mesophyll cells gaseous exchangevascular bundles transportstate the equation, in words only, for photosynthesisbriefly explain why most forms of life are completely dependent on photosynthesis Learning outcomesoutline the intake of carbon dioxide and water by plantsstate that chlorophyll traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent usesinvestigate and state the effect of varying light intensity, carbon dioxide concentration and temperature on the rate of photosynthesis (e.g. in submerged aquatic plants)

Photosynthesis isThe process by which light energy is absorbed by chlorophyll and transformed into chemical energy,

used in the synthesis of carbohydrates from water and carbon dioxide,

with oxygen being given off during the process.Plants use light energy from the Sun to power photosynthesis.

Where in the leaf does this reaction take place?

Photosynthesis takes place in what part of plant cells? Photosynthesis: where it happens

carbondioxidewater

light energy5Plant cell

Photosynthesis takes place in plant cells with chloroplasts.

Chloroplasts contain the green chemical called chlorophyll.Question:Do all plant cells contain chloroplasts?The Chloroplast

Photosynthesis occurs in 2 stagesLight stageDark stageLight-dependent stage(Light stage)

Light energy is absorbed by chlorophyll in the chloroplast.Chlorophyll converts light energy into chemical energy.Photolysis of water.Oxygen given off.Light-independent stage(Dark stage)

Photolysis of water.HydrogenOxygenCarbon dioxideGlucoseGlucose is formed using carbon dioxide and hydrogen atoms released during the light stage.Products of photosynthesisThe Overall Picture

Light energy is absorbed by chlorophyll in the chloroplast.Chlorophyll converts light energy into chemical energy.Photolysis of water.Oxygen given off.Carbon dioxideGlucoseHydrogenThe equationCarbon dioxide + WaterGlucose + Oxygen Light energyChlorophyll6 CO2 + 12 H2OLight energyChlorophyllC6H12O6 + 6O2 + 6H2OWhich of these products is used by plants?

What happens to the waste product? Glucose is the useful product for plants.

Some glucose is used straightaway by plant cells, some is converted to starch for storage and later used for food.

Oxygen is the waste product. Excess oxygen gas is transported out of the leaf into the air.

Photosynthesis: products of the reactioncarbondioxidewater

oxygenlight energychlorophyllglucoseoxygenglucoseWhy is this important for humans and other living things?15Light and Photosynthesis

Light and Photosynthesis

Limiting FactorsLight intensityCarbon dioxide concentrationTemperatureRecallLimiting FactorAny factor that directly affects a process if its quantity is changed.Light IntensityRate of photosynthesisCarbon dioxide concentrationRate of photosynthesisTemperatureRate of photosynthesisEffect of light intensity on photosynthesisRate of photosynthesisLight intensityLight intensityRate of photosynthesisAfter the saturation point, rate of photosynthesis remains constant, even when light intensity increases.Region ARegion BWhat is the limiting factor in region A?Effect of Carbon dioxide concentration on photosynthesisRate of photosynthesisCO2 ConcentrationCO2 ConcentrationRate of photosynthesisAfter the saturation point, rate of photosynthesis remains constant, even when CO2 Concentration increases.Region ARegion BWhat is the limiting factor in region A?Effect of Carbon dioxide concentration on photosynthesisCarbon dioxide makes up 0.03% of air.CO2 ConcentrationRate of photosynthesisup to the saturation point.

Rate of photosynthesisCO2 ConcentrationEffect of Carbon dioxide concentration on photosynthesisAfter the saturation point, further increase in CO2 concentration does not increase the rate of photosynthesis.

Rate of photosynthesisCO2 ConcentrationEffect of Carbon dioxide concentration on photosynthesis0.03% CO2 Light intensityRate of photosynthesis0.13% CO2 Increasing CO2 under experimental conditionsRate of photosynthesis increases dramatically.Effect of temperature on photosynthesisRate of photosynthesisTemperature40 oCAt 40 oC Enzymes are most active Rate of photosynthesis is at its maximumAt temperature above 40 oCRate of Photosynthesis slow down or even stopAt low temperatures, enzymes are less active, so the chemical reaction of photosynthesis takes slowly. As the temperature increases, enzymes become more active and the rate of photosynthesis increases.Effect of temperature on photosynthesisWhy does photosynthesis slow down or even stop at temperatures above 40C?

Chlorophyll Learning outcomesFate of glucosewhy photosynthesis is essential for life on earth.

Recall 3 classes of nutrients in animals. Fate of glucoseSTARCHGlucose temporarily stored

SUCROSETransported to storage organs for storage as starch or in other forms

GLUCOSECellular respiration Form cellulose cell wallAMINO ACIDSGlucose + nitrates form amino acidsExcess other parts of plant Synthesis of new protoplasm Storage of proteins

PROTEINSSynthesis of new protoplasm in leaves

FATSStorageCellular respirationSynthesis of new protoplasm

LightDarkSTARCHGlucose temporarily stored

SUCROSETransported to storage organs for storage as starch or in other forms

GLUCOSECellular respiration Form cellulose cell wall31Why is photosynthesis important?Sunlight Ultimate source of energy for living organisms

Plants are harness this light energy and convert it to chemical energy.

Photosynthesis make chemical energy available to animals. Why is photosynthesis important?Chemical energy obtained from photosynthesis is stored as glucose.Glucose carbohydrates, fats & proteinsPlants Food for organismsOrganisms obtain chemical energy directly/indirectly from plantsEaten byEaten byPrimary consumersSecondary consumersTertiary consumersProducersEaten byWhy is photosynthesis important?2. Photosynthesis also helps to regulate Earths environment.

Oxygen is used for respiration in living organismsSustains life on Earth

Removes carbon dioxide & produces oxygenWhy is photosynthesis important?Coal is formed from trees.Energy obtained from sunlight through photosynthesis is stored in coal. coal used as fuel.Energy is released when we burn coal. 3. Energy is stored in coal through photosynthesisRecapFate of glucoseStarch ,SucroseAmino acids ,ProteinsFatsImportance of photosynthesisPhotosynthesis make chemical energy available to animals. Photosynthesis also helps to regulate Earths environment. Energy is stored in coal through photosynthesis

Plant Fats

Learning outcomesInternal and external structures of the leafLeaf adaptation for photosynthesis.

External structures of a leafParts of the leafLamina (Leaf blade)Petiole (Leaf stem)Network of veins

LaminaPetioleLeaf picture obtained from http://www.greenmaidinc.com/Why-Clean-Green.aspx39External structures of the leaf

Adaptation of leaf to photosynthesisStructureFunctionPetiole (leaf stalk)Holds leaf in position to expose as much of it as possible to sunlight & airLarge surface areaTo absorb maximum sunlightThin lamina To allow sunlight to penetrate to all cells.To allow CO2 to diffuse in rapidly.Adaptation of leaf to photosynthesisStructureFunctionStomata present in epidermal layersTo allow CO2 and O2 to diffuse in and out.Air spaces in mesophyll layerTo allow rapid diffusion of CO2 to mesophyll cells.Xylem vessels within short distance of mesophyll cellsTo supply water to chloroplasts for photosynthesis.Adaptation of leaf to photosynthesisStructureFunctionPhloem tubes within short distance of mesophyll cells.To transport sugars away from leaf.Chloroplasts containing chlorophyll present in mesophyll layerChlorophyll absorbs & converts light energy to chemical energy used in the manufacture of sugarsAdaptation of leaf to photosynthesisStructureFunctionMore chloroplasts in upper palisade tissueMore light energy can be absorbed near the leaf surface.Leaf ArrangementsWhat do you notice about the arrangements?

Teacher to guide students to think about how much sunlight will each leaf/leaflet receive. Are any leaf/leaflet blocked by another leaf/leaflet?Expected observations: Leaves do not block each other from getting sunlight.Arranged in a way that allow leaves to get maximum exposure to sunlight. 45Cactus leaf adaptationsModified leavesNeedle-likeReduce water lossPhotosynthesis takes place in the stemContains chloroplasts.

HomeworkWorkbook Page. Due next Tue :45 4950 (4a and c only)53Plant Nutrition worksheet. Due next Wed.Section A: Q 1 20Section B: Q 1, 2, 4,5 Internal structures of a leafCuticleUpper and lower epidermisPalisade mesophyllSpongy mesophyll Guard cells

CuticleTransparent: allows sunlight to pass throughWaxy: Waterproof so prevents excessive water loss

Palisade mesophyll cells

Structure: Cylindrical and contains numerous chloroplasts Arrangement: closely packed below upper epidermis Function: Absorb maximum sunlight for photosynthesis Spongy mesophyll cells

Large intercellular air spaces: Allow rapid diffusion of gases through the leaf (Gaseous exchange) Few chloroplast: For photosynthesis Thin film of moisture covering cells: Allows carbon dioxide to dissolve easily.Spongy mesophyll cellsTransport tissues such as the xylem and phloem can be found here.Vascular bundleSpongy mesophyllSpongy mesophyll cellsVascular bundleXylem : transport water and mineral salts from root to the leaves

Phloem: Transports sucrose and amino acids from the leave to other parts of the leave.Guard cellsControls the opening and closing of stomaManipulating internal osmotic pressures and changes in turgidity

OPENCLOSEDStomataStoma

Water movementGuard cell StomaInto the cellTurgid Open Out of the cellFlaccidClosehttp://www.tokresource.org/tok_classes/biobiobio/biomenu/angiosperm_transport/index.htm55

Upper epidermis Palisade mesophyllSpongy mesophyllVascular bundleLowerepidermis Beech tree leaf

Palisade mesophyllSpongy mesophyllLower epidermis Upper epidermis Vascular bundle

Osmosis

Opening and closing of stomata

Guard cellsOpening and closing of guard cellsControlled by changing osmotic pressures

Similar to auto-swing doorsneed to use energy to keep it open

Auto swing shut when no one holding door open. Opening and closing of stomaDayStoma needs to remain open to allow exchange of gases. Might be close if:temperatures are highStrong windsNightStoma is closed to prevent excessive water loss

Opening and closing of stomaStomaGuard cellsEpidermal cellsDay- Opening guard cells

Movement of water.Potassium ionsIncrease solute in the cell

Decrease water potential in cell sap of guard cells. Epidermal cellsHigher water potentialGuard cellsLower water potential Potassium ions pumped into guard cells via Active TransportOpening of guard cells (Day)Entry of water into the cell will cause the cell to swell.Results in buildup of pressure exerted on the cell wall.Turgor pressure.

Inner cell wall thickerMore resistant to being stretched.Opening of guard cells

Turgid Guard cellsFlaccid Guard cellsCLOSEDOPENOpening and closing of stomaDayStoma needs to remain open to allow exchange of gases. Might be close if:temperatures are highStrong windsNightStoma is closed to prevent excessive water loss

Night- Closing guard cellsMovement of water.Potassium ionsSolute levels in the cell drops

High water potential in cell sap in guard cells. Epidermal cellsLower water potentialGuard cellsHigher water potential Guard cells stop pumping in potassium ions. Potassium ions diffuse out to neighbouring cells.Closing of guard cells (Night)Closing of guard cells

Turgid Guard cells

Flaccid Guard cellsCLOSEDOPENWater moves out of the cells by osmosis. Cells become flaccid and the stoma closes.How does carbon dioxide enter the leaf?Photosynthesis occurs.CO2 in leaf rapidly used up.[CO2] in leaf < [CO2] outside leaf.Diffusion gradient.CO2 diffuses into leaf through the stomata.CO2 dissolves into water on mesophyll cells.CO2 diffuses into cell.Leaf Structure & FunctionPlantsLeavesPhotosynthesishaveundergoStomataVascular bundlePalisade mesophyllSpongy mesophyllChloroplastcontainconsist ofProcessLimiting Factorsis ahasis required forPhloemXylemconsists ofTransportGaseous exchangeLeaf structureFunction72Carbon skinksAcarbon sinkis a natural or artificial reservoir that accumulates and stores somecarbon-containing chemical compound for an indefinite period.

Three natural carbon sinks : OceanForestssoilCarbon sinks

Carbon sourcesCarbon sinksCarbon SinksPlants take in carbon dioxide from the atmosphere for use during photosynthesis.Carbon SinksDeforestation Reduced our carbon sinksBurning of fossil fuels Increase the carbon dioxide in the atmosphereour carbon sinks will play a key role in controlling atmospheric carbon concentrationsCarbon Dioxide - Green house gas Global warming. Plant sciencesPlant tissue culture

Plant sciencesHydroponicsAeroponics

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Rainbow roses