|Explore||We know that plants need soil, water, and light to grow from our experiences outside of school. In class we discovered that plants photosynthesize and preform cellular respiration. Where do plants get their mass from?|
|Research Question||Do different plants photosynthesize at different rates?|
|Predictions||We think that plants do photosynthesize at different rates because of their size. The bigger the plant the more light it can absorb, then is photosynthesizes at a faster rate than smaller plants.|
|Experimental Design||We put 3 grams of three different kinds of plants (Submerged, terrestrial, and floating) in Phenol Red and put them under a light for 24 hours to see which would photosynthesize at the highest rate.|
|Conclusion||We found that the Elodea (the submerged plant) performed photosynthesis at the highest rate. The Phenol Red with the spinach (the terrestrial plant) stayed the same and surprisingly, the the Phenol Red with the Duckweed (the floating plant) turned yellow. We believe the reason for this is because...|
As this research project is now in the final stages of wrapping-up, we wish to thank everyone who participated in this inquiry; the students, mentors, teachers and others behind the scenes. We appreciate all of your efforts and contributions to this online learning community.
Scientific exploration is a process of discovery that can be fun! There are many unanswered questions about plants just waiting for new scientists to consider, investigate, and share.
After the end of the session, we will be updating the platform and archiving groups and projects, after which time new updates/posts will not be able to be added to projects or groups. Please come back and visit the PlantingScience Project Gallery anytime to view this project in the future. You can search the Gallery by keyword, team name, topic, or school name.
Good bye for now.
The PlantingScience team
It’s great to see that teams from your school are wrapping up and posting conclusions. Enjoy the final stages of your project, and feel free to post any final comments or questions you have for your mentors.
Dear Jeremy, Zachary, and Mercedeez
You are very welcome. In the 10 yr or so I’ve been doing this, you folks were probably the most involved and responsive group I’ve worked with. The pleasure was mine. I wish you well in your future studies.
Cheers, Dr. Dan
Dear Dr. Dan,
I would like to thank you for all the questions you have answered. We have learned so much about photosynthesis. Without you we wouldn't have been able to have the success that we did.
Hey, so I guess this is goodbye. Thank you for helping us with this thing it was a lot of fun. You’re my favorite scientist (even more than Bill Nye and the teacher from The Magic School Bus)
Dear Team 4:
Wow! Great experiment! I think it was a good conceptual design. Thanks for the data posts, Mercedeez. Though it is a little hard for me to see the solutions in the photos, except for your negative control (no plant in the solution), it looks to me like the elodea solution eventually turned almost purple. That’s way up on the pH scale (~8) about as far as phenol red can detect, so the results are pretty clear for that sample. One always has to be a little cautious because digital cameras can shift the color and so can a computer screen, and judging color is a little subjective anyway. But I think your results are pretty solid. Nice work!
And I agree with the logic of your explanation of the results. Not only are the duckweeds floating so only the undersides of the leaves are contacting the water, I think their stomata are entirely on the upper surface (typical of floating plants) so most of their photosynthetic CO2 would come directly from the air. Furthermore, they have roots in the water that would be doing respiration that would tend to lower the pH. Since your spinach leaves appear to be mostly intact (almost no cut edges for the solution to get into the leaves), unlike the leaf disks, their photosynthesis would be restricted. People often have the mistaken idea that water moves through stomata, but usually it is only water vapor that can do that (that’s transpiration). If there is air in the spaces inside the leaf water trying to get in through a stoma will form a strong meniscus from surface tension across the pore that will prevent the water from penetrating further. Water has amazing properties, and surface tension is one of them.
Zachary, you mentioned that the control solution got darker. Did it change color or just get darker? Over how long of a time was the cup left sitting out (I assume) uncovered? I’m going to guess it did not change color, because if it changed color most likely it would shift from orange to yellow (absorbed more CO2 to form carbonic acid) over time and seem to get lighter. On the other hand, since ionic solutes (stuff dissolved in water) like phenol red cannot evaporate, but the water can, a solution left exposed to air will lose water and become more concentrated over time. That’s my guess.
Jeremy, the answer to your question about Mr. Beast’s project actually is not simple. I’m going to answer yes, it will benefit the world by helping to make up for a small amount of the environmental damage that is reducing the number of trees worldwide. We have an organization here in the Cincinnati area that has a goal to plant 10 million trees in our area. My city (Hamilton) is an Arbor Society "Tree City" (your city may be too), and we (I’m a City Tree Board volunteer) are committed to planting 100s of trees every year to maintain and increase our urban canopy. I don’t know how many so far, but it is in the thousands.
To put things into perspective though, consider just the damage caused by the accidentally introduced, invasive emerald ash borer beetle. Since you live in Ohio, you may have heard of this monstrous little animal from Asia. Ash trees in Asia, which evolved for millions of years with EAB in their environment, have pretty good resistance to its damage, and only sick, stressed, and old ash trees are killed by it there. But in N. America the ash trees have little to no resistance to EAB. It is estimated that in the last 20 yr since it arrived, 100 million ash trees have been killed so far by EAB in Michigan, Indiana, Illinois, Ohio, Pennsylvania, New York, and Ontario, Canada. Other species of trees may take advantage of the newly available space and replace them eventually, that is if the invasive Amur honeysuckle shrub (also from Asia) doesn’t prevent new trees from growing. Then there’s all the damage from human-caused fires and deliberate deforestation for development to accommodate our rapidly expanding human population.
I do not want to discourage you though, there are millions of people who recognize that this is happening and are actively working hard to reverse the deforestation trend. I’ve planted 21 trees in my own yard to join the one lone hemlock that was here when I moved in 25 yr ago. Two of my fruit trees died from disease, but I replaced them with two native hazelnut shrubs that will get almost as big as the trees and feed me (and the squirrels) lots of delicious nuts. So, send a few bucks to Mr. Beast (I checked; it’s not a scam), whose organization has planted over 6 million trees so far. And get your student organizations to plant some trees at the school. Every tree planted will help reverse the trend - and make seeds that will help spread the trees further - and help limit global warming.
Cheers, Dr. Dan
Dear Dr. Dan,
The experiment was a success! We put 3 grams of spinach leafs, duckweed, and elodea into phenol red to see which one photosynthesizes the best. We found that the elodea photosynthesizes the best because the phenol red was a darker pink than the other cups of phenol red. We believe this was because elodea is meant to be under water unlike the other plants. The duckweed is naturally in the water but it floats on top of the water.
Hola, Dr. Dan, how are you?
So after our experiment we found that the control (Which was just phenol red in a cup) became slightly darker. Do you know why this happened? We can't figure it out.
A YouTuber that goes by the name of Mr. Beast started an organization that has a goal to plant 20 million trees($1=1 tree). They are doing it with money that is being donated to them. Will this have an effect in the world? If so, how much affect will this have?
What does photosynthesis make glucose from*? What molecules? Since all chemical syntheses require energy, what is the energy source? (I know you know that one! It’s in the name of the process.)
*Actually, photosynthesis makes two kinds of three-carbon sugars from which glucose can be assembled if the plant cell needs glucose. This is probably beyond what Ms. Dobson planned on telling you, but those two molecule types (glyceraldehyde and dihydroxyacetone) can be used to build lots of molecules that plant cells need, and they can be fed directly into the middle part of glycolysis, which conserves energy by skipping the energy-requiring first part.
So then, when a plant or animal cell releases energy from food molecules by respiration, where did that energy actually originate?
Best wishes, Dr. Dan
Dear Team 4:
I was discussing definitions with Ms. Dobson and one of the other mentors yesterday, and I ran across the following blunder in the dictionary on my computer (my trusty printed collegiate dictionary did not make this mistake). Can you spot what’s wrong with this definition?
respire | rəˈspī(ə)r |
breathe: [no object] he lay back, respiring deeply | [with object] : a country where fresh air seems impossible to respire.
• (of a plant) carry out respiration, especially at night when photosynthesis has ceased.
There is also a slight misconception conveyed in the definition of "respiration" in the same dictionary (also not present in my printed collegiate dictionary. This is why I think everyone should have a good-quality, printed dictionary of her/his own. Mine is a Merriam-Webster’s Collegiate 11th Edit.) The Internet has a lot of good information, but it also has a lot of bad information too. Printed materials from reputable publishers, like Merriam-Webster and your textbook publishers, have human editors with reputations to protect, so they try to prevent crap from appearing in their books.
respiration | ˌrespəˈrāSH(ə)n |
the action of breathing: opiates affect respiration.
• Biology a process in living organisms involving the production of energy, typically with the intake of oxygen and the release of carbon dioxide from the oxidation of complex organic substances.
I’ll explain this one. Notice it said "the production of energy". Well, respiration "produces" energy only in the same sense that burning gasoline does. The energy is not created; it is released from molecules of foo/fuel. The energy is trapped in the bonds (mostly) between carbon atoms in the food molecules, and respiration transfers that energy to cellular machinery where it is used to do work. When that energy is pulled out it causes the food molecules to fall apart, and the carbon (plus oxygen) gets released as CO2.
People sometimes make this same mistake by saying that photosynthesis creates energy. Nope. What does photosynthesis actually (literally) do?
Cheers, Dr. Dan
Dear Team 4:
Something else to think about —
1. The research question you posed on your project page was:
Do different plants photosynthesize at different rates?
2. And you hypothesized:
We think that plants do photosynthesize at different rates because of their size. The bigger the plant the more light it can absorb, then is photosynthesizes at a faster rate than smaller plants.
3. And then you stated in the "Experimental Design" section that you would do the leaf disk procedure with different kinds of leaves.
If you can handle a little criticism, I’d like to point out that the disk procedure will not compare plants of different sizes, but it is great for comparing leaves of different kinds (species) of plants. It is also good for comparing leaves of the same species but different ages. (Leaves at the tips of branches are younger than those located near the branch base.) That’s OK; I think you are able to revise #1 to "different species" and revise #2 … well, because of some other factor you can probably think of related to differences between species. Plant species do differ a lot.
But consider your original Question #1. What does "rate of photosynthesis" mean? Do you mean amount of food made per minute per plant? Logically, if two individual plants are the same species but different sizes, and everything else (like light, temperature, water and mineral availability) being equal, the bigger plant would would produce more food. Probably a better way to think of rate in this context would be amount of food per minute per gram of leaf biomass. That way you can easily compare different species to each other or plants of the same species but different ages (or sizes). The disk assay is perfect for that.
You can also test things like temperature or light color. Do you think photosynthesis rate would be different at different temperatures? What would that disk experiment look like?
Please try to find time to try to answer these questions. Dr. Dan