bhsdobsonfall2019 project 4

Project by group bhsdobsonfall2019


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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...
About this Project

This team did a great job designing an investigation around the different types of aquatic plants. They applied what we were learning about to what they see in their lives. Its great when what kids are doing in school melds with their experiences outside of school! Their mentor did a great job...

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Get to know your team’s scientist mentor, who will encourage and guide you through the scientific process of discovery. The more you share your ideas and research info, the more your mentor can help. You may also hear from a scientist mentor liaison who will be helping all the teams in your class.
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PlantingScience Staff
said
Farewell and Best Wishes
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.
Warm regards,
The PlantingScience team
PlantingScience Staff
said
Looks like you are in the final stages of your projects.
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.
Daniel K. Gladish
said

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

Jeremy
said

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.

Goodbye,

Jeremy

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Mercedeez
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Zachary
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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. 

Gracias, 

Zachary

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Jeremy
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Dear Daniel,

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?

Thank you

Jeremy

Mercedeez
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Daniel K. Gladish
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Dear Zachary:

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

Daniel K. Gladish
said

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 |

verb

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 |

noun

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

    Zachary
    said

    Hey sir, how’s it going? 
     

    Photosynthesis actually makes glucose. 

    Zachary

Daniel K. Gladish
said

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

    Jeremy
    said

    Dear Daniel,

    What we meant by "rate of photosynthesis" is which leaf discs float first. I like your suggestion of changing the temp. We would have 10 leaf disc in every beaker with the air removed from the discs. One beaker would have cold water, one at room temp, and one with hot water. We would blow into each of the beakers to add CO2. Finally put them under a light lamp and see how temp affects photosynthesis.

      Thank you, Jeremy

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Maria
said

Dear Dr. Dan 

Thank you for clearing up on what happened in our side experiment I had tryed to look up on the internet on how this was happening but didnt get vary far on looking for an explanation that made any sense. 

Daniel K. Gladish
said

Dear Team 4:

I was confused at first (misled by the photo-posts of breath-bubbled water), but I checked the color scale for phenol red (PR), and I see that a solution at pH < ~6.5 a solution with PR will be yellow, so the negative controls (distilled water without plants) would predictably be that color, as would PR water surrounding a plant held in darkness.  Even distilled water will become slightly acidic fairly quickly just sitting around because of exposure to the CO2 naturally in air, and the cellular respiration of elodea held in darkness would make the pH even lower because cellular respiration releases CO2, but that would not change the color perceptibly.  By contrast, according to the chart I obtained, the water around the photosynthesizing elodea was pH 7.5-8, which is pretty amazing given that the plant is simply removing the source of carbonic acid (that is CO2), not adding a base.

So, regarding your "side experiment", the PR water in the bottom of the test tube where the plant did not reach did not have to be bubbled with your breath to be yellow.  It would have been that way anyway from just sitting around.  Everything else I told you - about diffusion and all - would have still applied.

Cheers, Dr. Dan

Daniel K. Gladish
said

Dear Team 4:

There is one correction I have to make to your description on the data page.  In plants, respiration does not make photosynthesis possible.  It is the other way around.  Respiration requires food molecules (from photosynthesis) and aerobic respiration always releases CO2, which would lower pH and keep the solution yellow (like your plant in darkness) if it were not that photosynthesis removes CO2.  It’s worth mentioning that because plants need food 24/7 just like animals do, when the light is available they produce more food by photosynthesis than they need for respiration (the solution turned pinkish-red because of this).  This is because they have to make extra food molecules to get by when it is dark.

Your "side experiment" is interesting (I compliment you for thinking of it).  It reveals a phenomenon not directly associated with photosynthesis, but which relates to very many natural processes.  It is called "diffusion".  I wasn’t there to see what happened, but I do not think that the solution in the bottom of the tube was "turned light yellow" by the plant.  I think it just was already yellow from your breath and the plant did not have enough time to have an effect on the solution at the bottom of the tube.

The solution in the tube was "stagnant" (i.e., not stirred), so mixing of the solution has to rely on molecule diffusion, which is a process that relies on molecules wiggling around at a sub-microscopic level.  It is really slow, but if you had kept the light on and waited a really long time, I’d predict the solution would all become pinkish-red like it was around the plant’s leaves.

If you want to see this effect in a different way, just get two cups of water, put a gram of sugar in the bottom of each.  The sugar crystals will start to dissolve immediately in both  cups.  As you probably know, when sugar dissolves in water it disappears from our view because we cannot see individual sugar molecules spread out in the water.  On the other hand, if the water right next to a sugar crystal has a lot of sugar dissolved in it, that will slow down the rate that the crystal will dissolve.  If you do not stir the water (let it stagnate) the only process that will move the dissolved sugar molecules away from each crystal will be diffusion, which is slow.  If you gently stir the water at the top of the other cup the sugar crystals should dissolve much faster than in the stagnant cup.

Alternatively, with an eyedropper or pipet you could carefully put a little blob of food coloring at the bottom of each cup of water, gently stir the water at the top of one and let the other remain stagnant, then compare how long it takes for the color to mix evenly in each cup.  You’ll probably have to get some sleep before the stagnant one finishes mixing by diffusion - but it eventually will.

Cheers, Dr. Dan

Mercedeez
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Mercedeez
said

Dear Dr. Dan

We breathed into the cup with just water.

Claim - Evidence - Reason: (fixed)

We thought that the cup with baking soda water would float first.  We found that the leaves in the cup that we breathed into floated to the surface first. In 25 minutes, nine leaves in the breath cup floated to the top, while only six floated in the baking soda water and none in the control. When you exhale you release CO2, which plants use to perform photosynthesis. This is why the leaves in the breath cup floated first. 

 

Sincerely,

Mercedeez

Mercedeez
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Daniel K. Gladish
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Dear Group 4:

Yes, but what I was trying to explain with my little chemistry lesson was why baking soda dissolved in water is also a source of CO2.  You have empirically demonstrated that your breath bubbled through the water enhanced photosynthesis beyond the plain water control, probably because of its CO2 content, which is higher than in the ambient air.  Furthermore, your results suggest that your breath by itself is a better source of CO2 than baking soda by itself.  You can see the reason I asked if the breath solution also had baking soda; that would be two sources of CO2 together.  Logically, that would be better than either source by itself.  The fact that your breath by itself was better than baking soda by itself as a source of CO2 was a surprise to me.  Like you, I thought the baking soda would be better …. but that is why we do empirical experiments: to discover the real truth about natural things.

Let me ask, why do you think I mentioned fish and algae in my message to Jeremy?  Hint: CO2 and O2 are gases.  Fish need O2, but "breathe" in water.  Algae need CO2 but do photosynthesis underwater.  Does that tell you anything about gases and liquids?  What about your leaf disks?  Weren’t they effectively like algae underwater?  And then there is the buoyancy thing.  Some of the disks clearly increased in buoyancy.  Why?

BTW, I was wondering what do you think might have happened if you had waited longer before counting the disks?  Do you think if you’d waited longer the control disks might also have changed buoyancy and floated?

Cheers, Dr. Dan

Daniel K. Gladish
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Jeremy, like my answer to Zachary, I’m going to use questions to help answer your questions.  Try to answer them from your own knowledge first.  I want to clarify something about your procedure first.  Mercedeez, did you bubble breath into plain water or baking soda water?

There are two parts to the answer to your question, Jeremy: 1) What property of an object determines whether it floats or sinks in water, and 2) what process could cause that property to change.  I think you probably already suspect that #2 has something to do with photosynthesis because light was involved.  #1, though, doesn’t involve photosynthesis.  That is about buoyancy, is it not?  When you first punched out the disks, did they sink or float?  You said that all the disks sank at first (they were more dense than water, therefore not buoyant).  Did you have to do something to make that happen before putting the disks in your experiment solutions?  What did you do?  Mercedeez wrote something about this.  Why would that procedure change the density of the disks?

Later, after being illuminated for a while, the disks started to float.  What must have happened to their density (buoyancy) for that to occur?  What was going on that would make them more buoyant?  Now consider the general formula for photosynthesis (CO2 + H2O >> HCOH + O2) and consider where the stuff on the left comes from and where the stuff on the right ends up.

Let’s pause for a minute to consider some fundamentals.  Almost all eukaryotes (organisms with a nucleus in their cells) need O2 to do food respiration.  Plants and algae are photosynthetic eukaryotes, so they need the stuff on the left to make the carbohydrate building units (HCOH on the right) to make their food.  (They make all our food too).  Where do terrestrial (land) plants get their CO2 and H2O?  Where do they get their O2 for respiration?  Got the answer?  But you put the leaf disks under water.  No shortage of water, but CO2 and O2?  Hmmm…

Fish generally live underwater.  Fish are animals; all animals are eukaryotes.  Animals get their food by eating other organisms, but, since they are submerged, where do fish get their O2 to do food respiration?  Likewise, where do aquatic plants and algae that are submerged get their CO2 to make food?  Think a bit; by deduction what has to be the answer?

You all understand that there is more CO2 in the air you exhale than in the air you inhale and vice versa for O2.  That’s why we breathe.  Mercedeez didn’t specifically say it this way, but I think you may have used soda straws to bubble your exhaled breath into the test water.  Why do that?  That’s a lot like the way PepsiCo makes carbonated water.

Then there is the baking soda (sodium bicarbonate; Na = sodium, HCO3 = bicarbonate) water.  I know you guys aren’t chemists, but see if you can understand the following idea:  In water baking soda (NaHCO3) splits to form Na and HCO3.  Then the HCO3 becomes OH and CO2 dissolved in the water.  In other words, baking soda will release carbon dioxide (CO2) into the water, and this is especially true if something in the water keeps removing the CO2 when it appears.

I realize this is a lot of information at once, but you can ask me questions about any of it.

Cheers, Dr. Dan

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