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7.6 RESPIRATION IN 7.6 RESPIRATION IN PLANTSPLANTS

Plants less active than animals Plants less active than animals need lower energy requirementneed lower energy requirement

Gaseous exchange occur mainly in Gaseous exchange occur mainly in the leaves (large surface area to the leaves (large surface area to volume ratio)volume ratio)

By simple diffusion through the By simple diffusion through the stomata & the lenticelsstomata & the lenticels

Gaseous exchange in the lightGaseous exchange in the light Gaseous exchange in the darkGaseous exchange in the dark

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Gaseous Exchange in the Gaseous Exchange in the LightLight

During photosynthesising, the [CO2] in During photosynthesising, the [CO2] in the air space of the spongy layer falls the air space of the spongy layer falls below the 0.04%below the 0.04%

CO2 in the atmosphere CO2 in the atmosphere stomata stomata spongy layerspongy layer

O2 in the cells O2 in the cells stomata stomata atmosphere atmosphere Both respiration & photosynthesis occursBoth respiration & photosynthesis occurs The rate of both process depends on the The rate of both process depends on the

light intensitylight intensity

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Gaseous Exchange in the Gaseous Exchange in the DarkDark

Respiration alone is taking placeRespiration alone is taking place Less O2 inside the spongy layer than Less O2 inside the spongy layer than

outsideoutside O2 from atmosphere O2 from atmosphere lenticels lenticels

spongy layerspongy layer CO2 from cell respiration CO2 from cell respiration lenticels lenticels

atmosphere atmosphere

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Aerobic Respiration In Aerobic Respiration In PlantsPlants

Gasesous exchange can be Gasesous exchange can be investigated in the darkinvestigated in the dark

Glucose + oxygen Glucose + oxygen carbon dioxide + water + energy carbon dioxide + water + energyCC66HH1212OO66 + 6O + 6O22 6CO 6CO22 + 6H + 6H22O + 2880 kJ/ moleO + 2880 kJ/ mole

Carry out throughout the day & nightCarry out throughout the day & night In the light, photosynthesis is faster In the light, photosynthesis is faster

than respiration.than respiration. CO2 produced is quickly used up by CO2 produced is quickly used up by

photosynthesisphotosynthesis

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Anaerobic Respiration in Anaerobic Respiration in PlantsPlants

Occurs when O2 absent – alcoholic Occurs when O2 absent – alcoholic fermentationfermentation

Occurs in certain situation – flooding, Occurs in certain situation – flooding, initial stages of germinationinitial stages of germination

Glucose Glucose ethanol + carbon dioxide + ethanol + carbon dioxide + energyenergy

CC66HH1212OO66 2C 2C22HH55OH + 2COOH + 2CO22 + 210 kJ/ mole + 210 kJ/ mole Example : young rice plantsExample : young rice plants

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Respiration & Respiration & PhotosynthesisPhotosynthesis

Respiration is the reverse of Respiration is the reverse of photosynthesisphotosynthesis

Respiration uses the product of Respiration uses the product of photosynthesis, photosynthesis uses photosynthesis, photosynthesis uses the product of respirationthe product of respiration

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Compare & Contrast Respiration & Compare & Contrast Respiration & PhotosynthesisPhotosynthesis

RESPIRATIONRESPIRATION PHOTOSYNTHESISPHOTOSYNTHESIS

SIMILARITIESSIMILARITIES Both are metabolic processesBoth are metabolic processes

DIFFERENCESDIFFERENCES

A process of catabolismA process of catabolism A process of anabolismA process of anabolism

Occurs in all living cellsOccurs in all living cells Occurs in cells containing Occurs in cells containing chloroplast / chlorophyllchloroplast / chlorophyll

Take place in absence & Take place in absence & presence of lightpresence of light

Require lightRequire light

Uses glucose & oxygenUses glucose & oxygen Uses carbon dioxide & waterUses carbon dioxide & water

Produces CO2 & H2OProduces CO2 & H2O Produces glucose & O2Produces glucose & O2

Cell loses weightCell loses weight Cell gains weightCell gains weight

Chemical energy Chemical energy heat + heat + ATPATP

Solar energy Solar energy chemical chemical energyenergy

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Light Intensity & The Compensation Light Intensity & The Compensation PointPoint

Dark Dark no photosynthesis, respiration no photosynthesis, respiration continues continues CO2 formed & released CO2 formed & released

Light Light light intensity increase, the rate of light intensity increase, the rate of photosynthesis increasephotosynthesis increase

Compensation pointCompensation point is reach when all the is reach when all the CO2 produced in respiration by the plant is CO2 produced in respiration by the plant is re-used in photosynthesis & there is no net re-used in photosynthesis & there is no net loss or gain in CO2loss or gain in CO2

Compensation pointCompensation point = the LI at which the = the LI at which the rate of CO2 uptake (rate of photosynthesis) rate of CO2 uptake (rate of photosynthesis) is exactly equal to the rate of CO2 is exactly equal to the rate of CO2 production (rate of respiration)production (rate of respiration)

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TAMATTAMAT