What could be some measurable data in this experiment? (1 Viewer)

[pigas]

For agriculture we have to do an at-home experiment relating to plants and the effect of light. I wanted to do: "Does light effect the direction of plant growth?" with the hypothesis being: "The plant will grow towards the light source".

I need to include measurable data. I can only think of the angle at which the plant will grow. It of course has to relate the topic. Sure, I can measure the plant height every few days, but how could I relate it to the research topic? Anyone have any suggestions? I am trying to think of at least 3 - 5 as I need things like graphs, tables etc..

Or if not, any suggestions of other better experiments to do relating to the effect of light on plants?

Thanks

 

[MrsA]

BOS syllabus:
“perform a first-hand investigation to determine the effect of light on plant growth”
This is one of the mandated practical activities that appear in the syllabus and as such is examinable in the HSC exam, so it is worth planning and executing it well.
Definition of plant growth: An increase in the size of a plant
This means that the experiment needs to investigate the impact of light on the size of the plant. Generally this is assessed using dry weight as a measure rather than the height of the plant etc.
Your experiment is examining the development of the plant and how it reacts to direction of light so it is not really suitable for this particular purpose.

A more relevant experiment is to test plant growth under different light levels. Set up a trial with identically prepared trays of seeds in the same area, but some covered with shadecloth. Depending on your available resources you might have different grades of shadecloth. You can measure light intensity with a meter. Water all the plants the same and treat them in identical fashion except for the shadecloth covers. Once your plants have grown you can dry and weigh them to get results.
Interestingly the results you get will likely show that the more shaded plants will grow very tall and lanky as they attempt to get to more intense light conditions for more efficient photosynthesis. All the energy of the plants will be directed to this type of growth so the weight of useful product (depending on the type of plant you grow) will be significantly reduced.
This means that it is important to consider the type of plant you will grow and whether you will harvest the product separately from vegetative growth and report these as different figures.

Good luck!

 

[pigas]

Thanks for your help! I think I will use that idea instead. Only thing though, where do you think I could obtain the light intensity meter/whatever to measure the intensity with?

 

[MrsA]

Maybe your school science department would let you borrow one??? All schools now have these as they are needed for compulsory pracs.

Otherwise you could quote the light transmission that is given when you buy the shadecloth - eg 40%, 60% etc

I was also thinking that in order to keep the standardisation for the plants that are not covered by the shadecloth you might need to have some sort of wire or similar over the top of them that does not stop light.

I have seen this trial work well with radish plants when time was short. The leaf production ended up more in the shaded trays, but the radish root was much less so plenty to discuss and graph etc.