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Update: I have just received a grant to pursue this research. However, I must still perform the preliminary experiment described below before dipping into my very limited funds. Thank you for any ideas.

What are some accurate methods to measure the rate of photosynthesis that can be performed without access to a professional laboratory?

I am a citizen scientist who is designing a experiment to measure the rate of photosynthesis under different conditions. Although this idea stems from my interests as an amateur horticulturist, it has grown to into something of real scientific potential. However, I must conduct this experiment on a low budget without access to a professional laboratory.

Furthermore, I should note that it is almost impossible to quantify photosynthesis by measuring gas emissions in this scenario. The only way to keep the plants in a stable environment with equipment that I can afford is in an open, climate controlled room, (as opposed to a closed testing chamber that could trap gasses).

Any ideas on how to measure the rate of photosynthesis would be greatly appreciated.

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One of the simplest measures of photosynthesis is just measuring how much your plants grow (i.e., weigh them). Of course this technique is imperfect because of other influences on growth, the amount of time you have to wait to get a measurable change, and ideally you would want to use the dry mass of your plants to avoid water content differences, but you have opted to exclude the methods that get around those problems.

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  • $\begingroup$ Thank you for the suggestion. In fact, when running a similar experiment a few years ago, I quantified my results by taking the mass of each plant. You raise a good point about taking the dry mass though, a factor which I neglected to consider. However, I am trying to gather as accurate a data set as possible in order to show definitive correlation between photosynthesis and my variable (if any exists). That would give me some hope of taking this experiment to a university laboratory for further testing. $\endgroup$
    – Joe Smith
    Jun 12, 2017 at 22:24
  • $\begingroup$ Depending on your plant you might be able to mass only a part of the plant, like harvesting one of each of a leaf pair several days apart. You would compare the ratio of the second leaf to the first, in different plants that are your control/test groups. Whether that is feasible would of course depend on the growth pattern of your plant. Also if your hypothesis doesn't depend on a certain plant, you could use a fast-growing model species. Arabidopsis is a favorite in biology labs. $\endgroup$
    – Bryan Krause ♦
    Jun 12, 2017 at 22:31
  • $\begingroup$ My hypothesis does not depend on a particular plant. Thank you for the suggestion of Arabidopsis. Although I will do further research on that species, do you have any other suggestions for fast-growing plants that could be grown indoors from seed with a relatively small footprint (like growing in Jiffy Pot starter trays)? $\endgroup$
    – Joe Smith
    Jun 12, 2017 at 23:18
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If you dry the plant and use dry weight, that's how they measure photosynthesis, because all the carbon found in the plant is a balance of respiration at night and over-compensating photosynthesis in the day.

http://ibbiology.wikifoundry.com/page/Explain+how+the+rate+of+photosynthesis+can+be+measured

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  • $\begingroup$ Thank you for the link. It raises some interesting points that I will take into account. Overall, I believe that dry mass will be the most effective method for quantifying growth. However, I am always open to new suggestions as I design this experiment. $\endgroup$
    – Joe Smith
    Oct 11, 2017 at 22:28

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