Annette, Peyton, and Josh,

Thank you all for being a wonderful team to mentor! I was impressed by your experimental design, attention to detail, and gorgeous microscope images. Specifically, I thought it was smart to simulate the high smoke treatment by burning 2 strings instead of increasing exposure time. This meant that the control plants were exposed to identical conditions as the experimental plants, apart from the single independent variable (amount of smoke) in your experiment.

Your graph of leaf width looks nice – using a line graph makes it easy to see the trend of leaf width over time. To improve clarity, one suggestion I have is to add a label to your y-axis. I can understand that the y-axis indicates leaf width in cm from the title and legend, but I would add a label to reflect this. You can then remove the “(cm)” from your legend labels, as it will already be indicated in that y-axis label. Of course, any specific instructions you have from your teacher take priority over my suggestions!

Do you have quantitative measurements of stomata density? And if so, are you planning on making a graph with them as well? If you only took measurements at the final timepoint, I think a bar graph would be the best way to communicate these results.

When writing your report, think through your results carefully. Check my previous message about the products generated while burning the strings, and try to find some online references to help explain your results. Anything from a .edu site should be reliable, and there should be plenty of articles from university extension offices that are written in an easy to understand way. From some quick searching, here’s one that I found that may be helpful: https://botanicalgarden.berkeley.edu/glad-you-asked/amoke-ash-plants.

Thanks again for being a great team, and good luck with your final report!

Bryce

Thank you so much for all the help that you did for our project. This will be our last week of communicating. We are working on writing a formal lab paper, and our research is done. Thanks again

- Annette, Peyton, and Josh.

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The purpose of the copper wire was intially used to hold up the strings. Then they would burn evenly. Should we still include it in out experiment paper?

Hi all,

I see that you’ve filled out your project information with the results of your experiment and got a result that differed from your initial hypothesis. That’s totally fine (and it happens more often than you would think)!

But I’m a bit confused by your explanation – “The plant is trying to over compensate for carbon dioxide, causing higher stomata density.” Are you saying that the increased carbon dioxide experienced by the plants in the high smoke treatments caused the increase in stomata density? Because plants use carbon dioxide for photosynthesis, I think that more carbon dioxide would decrease stomata density, as the plant would be able to take up more carbon dioxide with less stomata.

Remember that carbon dioxide isn’t the only thing being produced when burning something! The combustion of a pure gas will generate products that are colorless (carbon dioxide, and sometimes carbon monoxide). But you're not burning a pure gas here. The smoke that you actually see when burning the string is mostly small, unburned particles of the string (aka ash). And because the string was soaked in potassium nitrate, there’s probably also some potassium nitrite being produced (though I’m guessing this is colorless). I’m thinking that this (ash + potassium nitrite) likely had a bigger effect on plant growth than any extra carbon dioxide being generated by combustion. Did you notice any smoke residue leftover on the leaves of the smoke-treated plants? Sorry if I led you astray with one of my earlier messages about combustion products!

Your experimental design is well written and very detailed. For your final report (if you have to make one?), I would make sure to add more info about the smoke treatments themselves. For example, include the number of strings that were burnt for each treatment, the length of the treatment, and the ages of the plants when you started the treatments and when you took your measurements. Also, what is the purpose of the copper wire? I don’t think you’ve mentioned it previously.

Are you planning on making a graph to visualize your results? Let me know if you need any help with this!

And finally, I think your work has relevance besides just smoke produced by forest fires. Air pollution and smog levels are increasing every year, making it harder for both us and plants to breathe. This means that understanding how air pollution affects plants is very important to plant scientists.

Okay thank you! The magnification was at 400x and Ill compare the photos to some online. 

Hi Annette,

Yup! The darker black dots should be stomata. In some of them, you can see a couple pixels of white in the middle - that should be the actual opening (aka "mouth") of the stomata. What magnification did you take these images at? It could be helpful to compare your images against some online examples taken at the same magnification. This would help you be more confident in stomata identification.

Hi Bryce I uploaded our three plants under the microscope, were thinking the blacker/ darker dots in the pictures are the stoma, would this be correct? 

That's a cool method of determining stomata density - I've never seen that before. If you're able to take a photo through the microscope of one of those epidermal impressions, I would love to see it. Excited to hear about your results!

We marked the leaves that looked like the same size and we will measure the leaves to determine the differences between the stomata, our hypothesis was the more exposure to smoke the more the stomata will reduce. So in the end the plant with two strings of smoke will have the least stomata density. 

http://resources.rothamsted.ac.uk/sites/default/files/groups/bioimaging_dev/Measuring%20Stomatal%20Density.pdf

this link will show you the method we plan to use to measure stomata density 

Photos look good! How are you planning to measure stomata density, and do you have any predictions about which plants will have the most stomata?

From their different heights, it looks like your plants may have germinated at slightly different times. To account for this, I would try to select leaves which are approximately the same size for measurements at the same time point. Smaller leaves may have higher stomata densities simply because the leaves are still expanding.

Hi Bryce

We ended up not doing the temperature testing, my teacher said the heat shouldn't be too much of a problem that it will affect the plants. We have 6 plants in each pot. We set up our gas chamber, to produce smoke we ended up soaking and drying an 8 inch piece of string in potassium nitrate and water, then we let the string on fire so it smolders creating smoke without a flame. We also decided to do one pot with no smoke, one pot that is in the gas chamber but with one string burning. Our last pot will be in the gas chamber for 10 min but we will be burning two strings creating more smoke. Ill be sending pictures of everything so far. 

Hi team,

Any updates on the temperature testing? How long are you thinking for the medium and long smoke exposure times? And are you including any replicates (i.e. multiple plants in each experimental group) in your experiments?

we didn't think of that, we will run a trial to see the temperature difference.

Using wood pellets to generate smoke is a good idea, and I like that you included a control. To know for sure that the smoke is causing any differences in growth you observe, it's important that the only differences between your treatments is the amount of smoke. Here's some extra things to consider:

1. Burning wood pellets will generate heat which may build up in the plastic container. Depending on the length of your smoke treatments, this heat may or may not matter. If you have the containers, wood pellets, and a thermometer, you could run a quick plant-free test to see if this heat results in a noticeable temperature difference.
2. It's possible that the plastic containers will act like mini greenhouses for the plants, trapping in heat. So even without the extra heat added by burning the wood pellets, the temperature inside the containers may be higher than the temperature outside. Again, the potential effect of this on growth depends on how long the plants will be in the containers. For shorter treatments (5-20 mins), I doubt that this will matter, but for longer treatments (1 hr +), it may be an issue. To deal with this, you could either find some way to control the temperature inside the containers (hard way), OR also stick your control plant in a (smoke-free) container for the same duration of your treatments (easy way).
3.  If you're taking chemistry, have you learned about combustion reactions? With photosynthesis in mind, notice anything interesting about the products of a complete combustion reaction? This isn't a concern, but just something extra to consider when interpreting your results.

Hi Bryce we're back from spring break and we have decided to go with the smoke experiment. We will use the pea plant and will measure different changes with the plant, including the stomata density and observational color changes. Our independent variables are one plant with no smoke, one plant with medium smoke time, and one plant with a long smoke time. To set it up we will have clear plastic containers and within we will light wood pellets on fire so we can get the smoke. All the plants will use the same soil and the same amount of water.