investigating the rate of photosynthesis , laws and artifically controlling plant growth

Describe the practical for investigating the rate of photosynthesis

• A source of white light is placed at a specific distance from the pondweed. You should then leave the pondweed for a couple minutes to adjust to the new light intensity before starting the experiment.

• When ready to start the pondweed is left to photosynthesise for a certain amount of time as it photosynthesises the oxygen released will collect in the capillary tube

• at the end of the experiment the syringe is used to draw the gas bubble in the tube up alongside a ruler and the length of the gas bubble is measured.

• this is proportional to the volume of oxygen produced.

• Repeat experiment twice with the light source at the same distance and the mean volume of oxygen produced is calculated then the whole experiment is repeated with the light source at different distances from the pondweed

What are the variables for this experiment

Light intensity- independent variable

Amount of oxygen produced- dependent variable

All others are control

Write out equation for inverse square law

Light intensity (proportional symbol ) 1/distance(d)2

How do farmers artificially create conditions required for photosynthesis

-in colder climates- Phone was often place crops in greenhouses which trap in heat (so it increases the temperature)

– They can also provide artificial light so photosynthesis can continue to occur all through the day and night

-Sometimes farmers may pump carbon dioxide into greenhouses or use paraffin heater which releases both heat and carbon dioxide as it burns

– Farmers may also use fertilisers to ensure plants have enough essential minerals and pesticides to kill any unwanted bugs

What is one problem that farmers may face bc of artificially controlling plant growth

Cost , controlluhg conditions in greenhouses are expensive