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Carbon Dioxide Release during Cellular Respiration in Seeds

Experiment video

What you will learn

Demonstrate that germinating gram/pea seeds release carbon dioxide (CO2) during aerobic respiration using an airtight conical flask with potassium hydroxide (KOH).

Materials needed

Germinating Gram (Chana) / Moong Seeds g
Germinating Gram (Chana) / Moong Seeds g
₹50
What is it?
Germinating Bengal Gram seeds (Cicer arietinum) with actively protruding radicles.
Specifications
Seed Quantity
50 grams soaked germinated seeds
Radicle Length
5 – 10 mm emergent white radicle
Viability
≥ 95% germination vigor
Conical Flask (250 mL) with single-bore rubber stopper
Conical Flask (250 mL) with single-bore rubber stopper
₹95
What is it?
Fresh 20% Potassium Hydroxide (KOH) analytical reagent pellets and solution.
Specifications
Concentration
20 g KOH pellets dissolved in 100 mL water
Purity
≥ 85% AR grade
Function
Rapid quantitative chemical absorption of CO2 gas
Small suspended test tube with thread
Small suspended test tube with thread
₹140
What is it?
Airtight respiration apparatus: conical flask, bent glass delivery tube, and suspended tube.
Specifications
Conical Flask
250 mL borosilicate glass
Delivery Tube
6 mm OD glass tubing bent at two right angles
Suspension Tube
10 mm × 75 mm miniature test tube
Potassium Hydroxide (KOH) 20% solution / pellets mL
Potassium Hydroxide (KOH) 20% solution / pellets mL
₹185
What is it?
Standard laboratory apparatus used in Carbon Dioxide Release during Cellular Respiration in Seeds.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Bent Glass Delivery Tube (U-shaped)
Bent Glass Delivery Tube (U-shaped)
₹230
What is it?
Standard laboratory apparatus used in Carbon Dioxide Release during Cellular Respiration in Seeds.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Beaker with colored water
Beaker with colored water
₹275
What is it?
Standard laboratory apparatus used in Carbon Dioxide Release during Cellular Respiration in Seeds.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard
Petroleum jelly (Vaseline) for sealing tub
Petroleum jelly (Vaseline) for sealing tub
₹320
What is it?
Standard laboratory apparatus used in Carbon Dioxide Release during Cellular Respiration in Seeds.
Specifications
Category
Biology Apparatus
Grade
CBSE / NEP 2020 Laboratory Standard

Tick items as you collect them. Tap + to see the product, specifications and buy options.

Stay safe

Apparatus must be strictly airtight; any air leak will prevent the water column from rising.
KOH solution must not spill onto the germinating seeds.
Use actively germinating seeds with emerging radicles for high metabolic respiration rates.
Ensure the delivery tube end is submerged well below the beaker water surface.

Steps

0 of 7 steps done

1Soak gram seeds in water overnight and keep in moist cloth for 24-48 hours to initiate active germination.
Observation
Soak 30 g gram or pea seeds in water overnight; allow to germinate on moist cotton for 24 hours until radicles emerge.
Safety
Select healthy mould-free seeds with active vigor.
2Place 30-40 germinating seeds in a 250 mL conical flask.
Observation
Place germinating seeds in 250 mL conical flask; suspend small test tube containing fresh 20% KOH solution using thread.
Safety
Handle KOH with forceps; highly caustic chemical causes severe burns if spilled.
3Suspend a small test tube containing freshly prepared 20% KOH solution inside the flask using a thread secured by the stopper.
Observation
Fit tight rubber stopper with single-bore hole carrying bent glass delivery tube into flask; seal with vaseline.
Safety
Ensure flask connection is completely airtight; coat stopper joint with petroleum jelly.
4Insert a bent glass delivery tube through the airtight rubber stopper.
Observation
Dip free end of delivery tube into beaker containing colored water; note initial water level at tube tip.
Safety
Keep colored water beaker stable on bench.
5Place the other open end of the delivery tube into a beaker containing colored water.
Observation
Set up identical control flask using boiled seeds soaked in 1% formalin to prevent bacterial decomposition.
Safety
Formalin is toxic; handle in ventilated area.
6Seal all stopper joints thoroughly with petroleum jelly to make the apparatus completely airtight.
Observation
Record water column rising to 8.5 cm after 4 hours in live seed flask, with 0.0 cm rise in boiled seed control.
Safety
Wash hands thoroughly after handling seeds and chemicals.
7Mark the initial water level in the delivery tube and leave the setup undisturbed for 2 hours. Note the water rise.

Tap + on a step to see what you will observe and any safety tips.

Record your observations

Time Interval (Hours)	Water Level in Delivery Tube (cm)	Net Rise in Water Column Δh (cm)	Control Flask Level (Boiled seeds)	Respiration State
0 Hours (Initial)	0.0 cm (Beaker baseline)	0.0 cm	0.0 cm	Setup assembled, zero net draw
1 Hour	1.5 cm	+1.5 cm	0.0 cm	Active cellular respiration begins
2 Hours	3.8 cm	+3.8 cm	0.0 cm	Continuous CO2 absorption by KOH
3 Hours	6.2 cm	+6.2 cm	0.0 cm	Steady vacuum suction head
4 Hours (Final)	8.5 cm	+8.5 cm	0.0 cm (No rise in dead seeds)	Conclusive proof of aerobic respiration

Tap a highlighted cell to write your own observation.

Result and conclusion

Water level in the bent delivery tube rises by 6.2 cm. KOH absorbs exhaled CO2, creating a partial vacuum inside the flask that draws water upward from the beaker.

C6H12O6 + 6 O2 -> 6 CO2↑ + 6 H2O + 38 ATP; 2 KOH + CO2 -> K2CO3 + H2O (Vacuum creation)

Observation	What it means
Respiratory CO2 Absorption	Germinating seeds consume O2 and release CO2; KOH solution in suspended tube absorbs CO2 forming soluble K2CO3.
Partial Vacuum Formation	Because released CO2 is chemically trapped while O2 is consumed, gas pressure inside sealed conical flask drops.
Hydrostatic Water Column Rise	Atmospheric pressure pushes beaker water up bent delivery tube by 8.5 cm, directly proportional to absorbed gas volume.
Boiled Control Inactivity	Boiled dead seeds treated with formalin show zero water rise, confirming respiration is an exclusive property of living germinating tissue.

Water Column Rise in Delivery Tube vs Germination Respiration Time

Sample readings. Replace with your own results.

Experiment photos

Before the experimentDuring the experimentResult