To Investigate the Effect of Water, Oxygen and Temperature on Seed Germination

Textbook Diagram: set up of the apparatus

• Four small clear glass jars kept in darkness.
• Jar A: water-soaked seeds on soaked cotton wool, open to air at 20ºC.
• Jar B: dry seeds on dry cotton wool, open to the air at 20ºC.
• Jar C: 4°C – water-soaked seeds on soaked cotton wool (in a fridge) open to the air.
• Jar D: water-soaked seeds at 20°C in a sealed jar that does not have oxygen in the air – oxygen removed by pyrogallol or wet iron filings on filter paper.
• One week later check the results.

Results

• A: water, oxygen and suitable temperature together present / germination.
• B: no water / no germination.
• C: low temperature / no germination.
• D: no oxygen / no germination.

Conclusion: water, suitable temperature and oxygen are together required for seed germination.

To Show Digestive Activity During Seed Germination

Textbook Diagram: set up of apparatus

• Soak maize seeds in water for two at 20°C – stimulates germination.
• Place half of the seeds in boiling water to kill them.
• Cut the seeds in half so the entire plant embryo is only in one half.
• Sterilise the seed halves in disinfectant solution – no digestive activity of micro-organisms.
• Rinse seed haves in sterilised water.
• Sterilise forceps by flaming.
• Use forceps to place seed halves with live embryos into the sterile starch agar in a petri dish.
• Repeat for seed halves with dead embryo in a second sterile starch agar plate – control plate.
• A third unopened starch agar plate is used as a second control.
• Minimum opening of plates when placing the seed halves.
• Sterilise the forceps after transferring the seed halves.
• Incubate all plates upside down for 3 days at 20°C.
• Open plates and remove the seed halves.
• ‘Flood’ the plates with iodine solution.
• Let soak for 2 minutes and pour off the iodine solution.

Results:

• Unopened plate: uniformly blue-black – no starch breakdown.
• Dead Embryos: uniformly blue-black – no starch breakdown.
• Live Embryos: yellow-brown areas at seed sites – starch breakdown.

Conclusion: starch digestion occurs during germination.

• Repeat to verify the results.

The Syllabus Also Requires You To Know:
Definition and advantages of “dormancy”.

• Mention of dormancy in agricultural and horticultural practices.
• Germination: definition, factors necessary, role of digestion and respiration.
• Stages of seedling growth.
• Vegetative reproduction.

Practical Activities:

1. Investigate the effect of water, oxygen and temperature on germination.

2. Use of starch agar or skimmed milk plates to show digestive activity during germination.

Seeds - Dispersal and Germination

Seed Dispersal

Seed dispersal is the scattering of offspring away from each other and from the parent plant.

Дата добавления: 2015-11-14