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

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.

@Gracie: If I follow you correctly, this means that the plant grew higher when the light was not coming directly from above?

@Emily: That's an interesting observation. BTW, plants don't perceive green light (that's the reason why plants are green, the chlorophyll (which is the green pigment giving the leaves its colour) is absorbing light radiations with an exception for wavelengths corresponding to green colour in the visible spectrum).
I also think it might come from the quantity of light perceived by the plants rather than water (especially if you watered all the plants equally).

As a general question: When you measure the plants, do you place them upright to measure the stem length? Didn't you observe that the plants are leaning towards light. I recommend you to google "phototropism" to have a look at what I mean.

great job all of you

hello, you are doing a great job so far. I am a little curious, did you notice anything special regarding how the plants are growing depending of the light angle, besides the height?

Hi Thomas, we have noticed that the plants have grown towards the light. The final measurements for the plants were plant 1: 10.5 cm, plant 2: 12 cm, and plant 3: 11.5cm. 

Hi! We watered our plants after not watering them over the weekend. For each plant, we watered them approximately half a plastic cup of water. Plants 2 and 3 were bottom watered and Plant 1 was watered normally, like the last time. We then measured the height again: Plant 1 is 8cm, Plant 2 is 9cm, and Plant 3 is 10cm. The variation in the height could be a result of the soil, because I've noticed that the soil could be dense or lightly packed, which could take away from the true height of the plant. There could also be human error because the plant might not be held straight enough for measuring. The measuring might not be done accurately. All of these sources of error could be a factor in the results of the lab. 

Hi! Today we watered our plants after a few days with no water. I bottom-watered plants 2 & 3 with approximately half a plastic cup for each plant. I also watered plant 1 half a plastic cup of water, too. We then measured the new height of the plants: plant 1 is 9 cm tall, plant 2 is 11 cm, and plant 3 is 9 cm. These measurements were taken from the soil to the the tallest plant in the cup. It doesn't seem like the plants were affected to much from the lack of water, but they have been responding well to the light treatments. We will be sure to keep you updated on any progress. 

Update:

We watered the plants with 30 c.c. yesterday and 10 c.c. today. We also put it under different light angles for each plant. One 90 degree angle, second 0 degree angle, and third 45 degree angle. We will start observing progressing changes.

Hi! We also decided to remove the plants from the plastic cups they were in so thee light could truly be horizontal. Because of this, we decided to "bottom water" our plants by tilting a tray and placing the plants at the bottom so water would gather. In addition to the 10 mL of water we added before setting up our actual light-angling experiment, we added approximately half a plastic cup of water to each of the trays. We will be sure to note any progress and/or changes in our experiment.

Hi! Yesterday I watered the plants with 30mL of water. We set up our experiment today because all of the plants have started to grow. We watered all of the plants with 10mL today. Here is the data we collected for today.

Plant 1- light angle 90^o (vertical)

Plant 2- light 0^o (horizontal)

Plant 3- light 45^o

Height recorded based off of the tallest plant.

 

	Plant 1	Plant 2	Plant 3
Height initial (cm)	6cm	11cm	7cm

Hi! I will be sure to double check with my peers tomorrow, but I think it took about 9 days between when we planted the seeds and when we saw them germinate. I think this number would have been a little shorter if we had put them in a water-retaining container sooner, but we will probably begin our lighting experiment this week at some point. On Friday, we added approximately 30 mL of water to keep it moist throughout the weekend since no one would have been around. We will be sure to keep you updated on any progress tomorrow when we meet for class. Thanks!!

Great!! congratulations!!!!!!

Just by curiosity, how long did it take in total for the seeds to germinate?

Hi! After placing the peat pots in the plastic cups and giving them a more generous amount of water (50mL), two seeds started to break through the soil in cups 1 and 3. Today we only added 20 mL of water to the cups so we don't overwater. We don't have class tomorrow but we will have someone in our group swing by tomorrow to check any progress and water the plants again.

Hi!

Yesterday we added more water than we have been in the past. This new set up was hoped to assist in growth through "bottom watering" as had been suggested. Today we checked the progress and we can tell there has been growth so far. We will keep you updated!

Katie

Update:

It started growing! Container 1 and 3 plants broke the soil. We watered each plant again with 30 cc of water. Hopefully plant 2 is going to grow. I think 30 cc of water is the best amount to water each day since it grew from last time. We will keep you updated.

Correction: we watered them with only 20mL of water, not 30mL.

The bottom watering worked! Plants 1 and 3 have started to grow. We watered each plant with 30mL of water today because the top of the soil was still a little wet. We will check back in tomorrow to see if plant 2 starts to grow. Once they have all started to grow we will set them under different angles of light. 

We added more water this time than in the past because we predict that most of the water will go through the peat pot again. This water will than gather in the plastic cup and continue to water the plant from the bottom like Viviana suggested. Thank you for the help!

Update:

Yet I still don't see any growth from the plants. The plants still haven't broke the soil yet. We added 50 ml of water again into each cups. Hopefully we are not under watering or overwatering the plants. We are trying to figure out the amount of water that would make it grow. We will continue to keep you updated, thanks.

Hi, today we are placing the peat pots into plastic cups to hopefully retain more water than before. In addition, we are adding 50 mL of water to each of the pots/cups to play around with which water amount our seeds like the best. There is still no noticeable difference in the growth, but hopefully placing the pots into the cup will help with plant growth.

it is indeed quite important to keep the soil moist but don't overwater either. Seeds need oxygen to germinate as well as seedlings need it to grow. Just follow the instructions given by Viviana and that should help a lot

Update:

There was not a significant of growth for the plants. We think that adding more water might help it grow. We added 30 c.c. of water each container, and hopefully it will grow. We also placed the pots into plastic cups, so we can make sure the water stays there. We will keep it updated, thanks!

Thank you Thomas and Viviana!

I do suspect that a lack of water is the issue, so we are going to place the current pots inside of plastic cups so that the water doesn't escape. The top was dry again today with still no growth. We watered it with 30 mL again. I predict that this change will result in growth because other groups in our class that used plastic containers have plant growth occurring. 

I will keep you updated, Grace.

Hi! Today we added approximately 30 mL of water to the plants. There is still no noticeable growth, at least any growth that has broke through the soil. I think the problem is that none of the water is being contained in the pot, so minimal water is actually saturating the soil long enough for the seed to use it and grow. To remedy this, I think a plastic cup large enough to fit around the peat pot that we are currently using could be used; we would simply have to place the peat pot inside a plastic cup. Another option would be to just transfer the seeds into a plastic cup all together. In general, I think the only thing wrong with our experiment so far is that a water isn't saturating the soil and the seeds enough and/or for a long enough time. We will keep you posted! 

indeed, it can take longer for the plants to germinate. You just have to be patient. As I said to another group, make sure that the surface of the soil is kept moist and water the pots by the bottom. That way, when the top is moist, it means that all the soil is also humide.

good luck and have a nice weekend

Update:

The plants are still under the lights. We added 30 ml of water to each plant. I did not really see any growth of the plant. It is still under the soil, but we can be patient and keep waiting. I will keep it updated.

Hi Thomas!

Yesterday we did nothing to the plants, except left them under the light as normal. We added 30 mL of water to each plant as well. No noticeable growth beyond the soil has occurred yet, but that is completely fine because it has only been 4 days since we even planted the seeds.

Hi Thomas,

Today we added 30mL of water. The soil was dry because we did not have class yesterday and the plants went 48 hours without being watered. There is still no plant growth, so I will be more cautious of the plants having enough water.

Concerning the amount of water to put, it strongly depends on the humidity in the room. Just make sure that the surface of the soil is moist (or at least not completely dry).

Maybe you can wait a couple of days between the seed break and the beginning of the experiment as the first few days, plant growth is not exclusively related to light perception but also depends on the storage in the seeds. In your case, there is really little storage in the seeds so that a couple of hours should be enough but better play safe and wait a 1 or 2 days.

Hello! So far, our lab is going well. We have performed all of the steps of the procedure to set it up, and now we are just waiting to begin seeing results. We have kept the amount of water (25 cc) the same, the light have remained constant, and we are hoping that our lab continues on the right path. Beekeeping everything that could possibly derail our experiment under control in terms of consistency throughout our samples, we lessen the amount of room for error when looking to find how the angel of light affects the rate of photosynthesis (our essential question). We will not be on again until friday because we do not have class, but we are looking forward to sharing our progress!

Hi! Today is Day 3 of our experiment. We added approximately 25 mL of water to eat peat pot both yesterday and today. Do you think that is enough water for every 24 hours? It seems like the water is being completely absorbed by the saturation seen with on the pot, but I just want to be sure that there will be enough water for a 24 hour period. So far, there isn't any plant growth, but I will be sure to keep you posted on the progress of the experiment. Once the seeds break through the soil, we will begin our experimentation with the effect of the angle of lighting. 

We don't have class tomorrow (Thursday) so we won't be able to check the progress until Friday, and we will be sure to update the feed concerning any progress seen in our experiment. I don't suspect that any growth will appear until after the weekend, but that depends on if and how much water it receives over the weekend. I look forward to hearing your feedback!

Hello. That is a nice experimental design. @Gracie, it is a really good idea to first check that there is no variation between the "samples" before the beginning of the experiment.

Just keep going, you are on the right track. Looking forward to seeing what results you will obtain.

Good luck

Update: We added additional 25 cc of water to each plant. They have been under the light the whole time since the experiment has started; someone accidentally took it off the light by a couple seconds, hopefully that wouldn't affect the whole experiment. 

Hi Thomas,

Today we added 25 mL to each plant. They are under constant light. Do you have any suggestions or concerns with the idea of starting the plant growth before testing the effects of light angle on its growth? The reason we decided to do it was to make sure that each container contains seeds that are not defective, or in other words they won't have an issue growing for reasons outside of the light angle being tested.

We began conducting our radish seed lab today. Below is the procedure we plan to follow for this experiment. So far, we have carried out the preparation steps 1-3, and the potted seeds are ready to be used. Looking forward to telling you more as the lab moves forward!

As of right now, the experiment we're going to run is as follows:

Group 2: Gracie, Emily, Katie, Ron

 

AP Biology

Mrs. Cost

21 October 2019

 

Radish Seeds

 

Purpose: 

The purpose of this experiment is to test whether or not different angles of light affect the growth of radish seeds.

 

Hypothesis:

I hypothesize that a vertical flow of light (directly above the seed/plant) will result in the most growth of the radish seed due to the fact that at 90o the plant will receive maximum light exposure and smaller angles will receive a lower light exposure. Because light is a reactant of photosynthesis, the most amount of light a plant can receive will result in more photosynthesis reaction, which will cause more plant growth.

 

Materials:

• Radish Seeds

• Soil  (Note: Brand of the soil is “Jiffy”)

• Containers for planting

• Artificial lighting (3)

• Water

• Books (or something else to elevate the light to the desired angle)

• Tape 

• Two boxes 

 

Procedure:

1. Plant radish seed into a container full of potting soil. Make sure the seed is covered with soil

2. Water the seed until the soil is moist.

3. Repeat steps 1 and 2, two additional times for a total of three plants.

4. Place all three plants under the same artificial light at 90o until all of the seeds have started to grow through the soil.

5. Record the initial height of the plants.

6. Place one plant under a light elevated at 90o (directly above the plant by hanging the light)

7. Using books elevate the remaining two lights to 60o and 30o, respectively.  

8. Separate the three plants by placing a box in between them so that the different lights don’t affect the experiment.

Update: We put approximately 20 ml of water in each of the container.

Update: We are currently doing the radish seeds light angle experiment. We planted 5 seeds in each container, and the container is 2.5 inches in diameter. We used "Jiffy Natural and Organic" soil; the brand of the soil is "Jiffy".

If you really want to look at the plants before stopping the experiment, you should shut every source of light and use a green lamp (plants don't perceive green light) but that might be a little tricky to establish as you should really avoid any source of white light (even dimmed...)

Thank you.

We will measure the final biomass when we get back to school on Wednesday. Today we just checked on the experiments under the light and took pictures of them. The experiment with water started to grow and the one without water did not. We added and additional 2mL of water to the water and light dish. We took your advice and did not check on the seeds in the dark, so that we wouldn't effect our final results. 

Just a quick advice. On top of measuring the biomass, I would also recommend you to take a picture of the plants. You should be able to see something interesting

Hi, we are about to have a 4 day weekend starting Saturday. So we are not going to start the different angles of lightings lab yet. But we did start a lab on "Where do radish seeds get their mass from?". Before we started, I predicted that the mass of seeds with lighting and water, and the seeds with just water would increase their mass. I also predicted the seeds with no water and just light would not increase its mass. To set up the experiment, we have three petri dishes placed with paper towel at the bottom and the seeds on top. We added 2 ml of water in petri dish 1 and 2. We then placed petri dish 1 and 3 under the light, and petri dish 2 without light. We will come back from long weekend and hopefully be able to see great results. Looking forward to it, Thanks!

Hi Thomas!

We are going on a long weekend and we decided this was the best time to begin a new experiment. We are pushing back the radish seed lab we were planing on until we get back on October 16th. Until then, we decided to do a different radish seed lab to test the essential question of "where do plants get their mass? To answer this, we will have three petri dishes with radish seeds in them, experiencing different conditions.  Inside of the petri dishes, we placed paper towel with seeds on top. Each dishes different, so in dishes 1 and 2, there was about 2 mL of water on the paper towel, and in petri dish 3  there was no water. Petri dishes 1 and 3 are under light the classroom and dish 2 is inside a dark drawer which we will not open until we get back on the 16th. When we return, we will observe the changes, and collect data which we will share with you. Talk soon!

hello, that sounds like a good experiment. I would just advice to keep the drawer closed during the whole experiment and open it only at the end. There are indeed some mechanisms that can be induced in plants by a really short light flash. To avoid that, just keep your seeds in the dark all the way.

Hi! We have a long weekend coming up so we won't be in school for 5 days. Because of this, we decided to postpone the original radish seed lab until we get back next Wednesday (Oct. 16). As a class, we decided to use spare radish seeds and perform an additional experiment that requires less interaction on our part so we can come back on Oct. 16 and see progress.

For this additional experiment, we wanted to answer the essential question: Where do plants get their mass? To answer this question we decided to grow spare radish seeds under different conditions to see which condition resulted in the biggest increase in mass. Got got three petri dishes and placed paper towels in the lid of the petri dish. We then got a sample of seeds from Mrs. Cost which were placed into each petri dish, making sure to keep measuring the mass throughout the experiment. Once the seeds were on top of the paper towels, we saturated the paper towel and seeds with approximately 2 mL of water in petri dishes 1 and 2. Petri dish 3 does not have water. The other variable we are testing is how exposure to light can affect plant mass and growth. Petri dishes 1 and 3 are under artificial lighting in the classroom while Petri dish 2 is in a dark drawer. 

Our group will check the progress of the seeds when we return to classes on Oct. 16 and compare the results to our hypotheses that we created today prior to experimentation. Please let us know if you have any suggestions for the improvement of the lab! 

Hi Thomas, thank you for the suggestions. I'm not sure if we have a set timeline yet but if I had to guess it will probably be at least a week. We are about to have a short vacation from school starting Friday after noon until the 16th. Because of this break we won't be starting the light angle lab this week. Instead we are doing a lab to test where plants (radish seeds) get their mass from. As a class we predicted that water and nutrients, such as CO2, contribute to plant mass. From this prediction we set up a lab where dish #1 contains about l.0g of radish seeds, about 2mL of water and constant light, dish #2 contains 1.0g of radish seeds, about 2mL of water, and no light, and dish #3 contains 1.0g of radish seeds, no water, and constant light. All dishes were in the same type of container and contained a folded paper towel under the seeds. I predict that the seeds with water and light (dish #1) will increase in mass the most, the seeds with just water (dish #2) will increase in mass by absorbing the water, but will not grow as much as dish #1, and that the seeds with light and no water (dish #3) will decrease in mass because they will get dried out. We recorded the initial masses of the lids without seeds, with seeds, and then with again with water if it was added so that will will have something to compare the final masses to. Please let me know if you have any questions or suggestions. Thank you! -Grace

 

Hello everybody, the seed growth experiment you are suggesting sounds really promising. I would recommend to avoid having to many plants per pot as it will generate some shadow for the neighboring plants and might raise wrong observations. Maybe just 2 or 3 per pot might be enough.

Concerning the type of soil, that would be great if you could have access to some soil used for gardening. Otherwise, any soil can be used as long as it is the same for all the pots (make sure to mix it carefully between distributing it in the pots to avoid any variation).

I have then a more general comment. You are planning to check the effect of light angle on growth rate. How long are you planning to keep the experiment running? I would recommend you to make sure that, once the experiment is set up, you don't turn the lamp or the pot for your observations, you should then observe something really interesting...

How many radish seeds should we be planting in each pot in order to collect the most accurate and successful data?

Which type of soil would be the most ideal for planting our radish seeds in?

This is my lab design for the Radish Seeds Lab

Purpose: 

Find out if position of lighting affect the growth rate of radish seeds

Hypothesis:

I hypothesize the vertical position would have the fastest growth rate since it is exposed to the most light.

Materials:

• Radish Seeds

• Soil

• Plant container

• Artificial lighting

• Water

Procedure:

1. Position three lights with three different angles, 60 degree, 90 degree, and 120 degree

2. Plant containers under each artificial light

3. Plant radish seeds inside the plant container

4. Water the seeds

5. Observe the growth rate

Group 2: Katie, Gracie, Ron and Emily

AP Biology

Mrs. Cost

2 October 2019

Leaf Disk Lab

Our purpose, materials, procedure, hypothesis, and data are all the same.

Analysis

In this lab, each member of our group collected appropriate leaves to test the rate of photosynthesis on a leaf with different conditions. We were advised to steer clear of browning, decaying, or veiny leaves. We ultimately tested a large, healthy, green leaf, and carefully selected our disk samples from areas of the leaf that had minimal veins. We punched 24 holes out of the leaf, and placed 12 into the breath treatment and the other 12 went into the baking soda treatment. We filled cups with water and put 3 drops of diluted liquid soap into both of them. We put 12 of the disks in a syringe with the breath solution. We placed a finger over the tip of the syringe and pulled the plunger waiting for all of the disks to go to the bottom of the syringe. When they all sank we put them into their cups. We did the same thing for the baking soda treatment. We then put both cups containing the treatments and disks under the light.

The baking soda produces carbon dioxide gas, which is combined with water, and artificial lighting made 7 of the 12 disks float, which means that they were able to perform photosynthesis and produce oxygen gas which made the disks to float in that treatment. The breath treatment didn’t work as well as the baking soda treatment, in the fact that it didn’t result in photosynthesis.

Conclusion

My lab group and I were successful in following the procedure, and we collected the desired data. The purpose of the experiment was to find out if the rate of photosynthesis would be affected by different treatments and find if there was any difference in data regarding photosynthesis between the two treatments. Our original hypothesis was that the leaf disks that were exposed to the breath solution would rise faster, and the baking soda treatment would float, but at a slower rate. This was because the level of carbon dioxide produced by baking soda was different than the level in the breath treatment.

The baking soda treatment disks floated faster than the breath treatment, so out hypothesis was not supported by our collected data. 

Purpose, Hypothesis, Materials, Procedure, Data, are all the same as my other group members.

Analysis

 In this leaf disk flotation lab, our group first picked out a fresh leaf without furry hair. It was big enough for us to hole punch 24 leaf disks out of the leaf. Twelve of the leaf disks were put under the testing of breath solution, the other twelve was under the testing of baking soda solution. Before the leaf disks were put under artificial lighting, 12 of the leaf disks sank in the second try in the breath solution. In the baking soda solution, 12 of the leaf disks sank in the first trial. When leaf disks were put under artificial lighting, none of the leafs in breath solutions float. In the baking soda solution, 1 started floating 9 minutes, 2 after 19 minutes, and 7 after 24 hours. After 42 hours no disks were floating in both solutions.

Conclusion

The results did not support our hypothesis. Before the experiment, we hypothesized that the leaf disks exposed to breath treatment would rise to the surface faster because they will be exposed to higher levels of carbon dioxide and will have a faster rate of photosynthesis compared to the baking soda solution. It turned out to be false. Under the artificial light, the leaf disks in our baking soda solution actually turned out to float more and quicker than the breath solution. The breath solution didn’t even have one disk floating. I think that it is because the sodium bicarbonate in baking soda dissolved in water forms more CO2 than the breath solution. When undergoing photosynthesis, the amount of CO2 affected the rate of photosynthesis causing leaf disks in baking soda solution to float way faster than the leaf disks in breath solution. In this experiment, we could possibly made errors on the amount of baking soda and soap, and not putting both solutions under the artificial lights at the same exact time. The breathing method could also had a lesser effect than we thought it would, the CO2 escaped the solution before it could even contact the leafs. 

Here is our Lab for tomorrow to test how the angle of light effects plant growth. Please let me know if you have any suggestions! Thanks, Grace.

Radish Seeds

 

Purpose: 

    The purpose of this experiment is to test whether or not different angles of light affect the growth of radish seeds.

 

Hypothesis:

    I hypothesize that a vertical flow of light (directly above the seed/plant) will result in the most growth of the radish seed due to the fact that at 90o the plant will receive maximum light exposure and smaller angles will receive a lower light exposure. Because light is a reactant of photosynthesis, the most amount of light a plant can receive will result in more photosynthesis reaction, which will cause more plant growth.

 

Materials:

• Radish Seeds

• Soil

• Containers for planting

• Artificial lighting (3)

• Water

• Books (or something else to elevate the light to the desired angle)

• Tape 

• Two boxes 

 

Procedure:

1. Plant radish seed 1 inch into the container full of potting soil.

2. Water the seed until the soil in the container is moist.

3. Repeat steps 1 and 2, two additional times for a total of three plants.

4. Elevate the angle of one light to 90O (directly above the plant by hanging the light)

5. Using books elevate the remaining two lights to 60o and 30o.  

6. Separate the three plants by placing a box in between them so that the different lights don’t affect the experiment.

My purpose, hypothesis, and data is the same as Emily's.

Analysis 

    In this lab my partners and I gathered healthy leaves from outside to use for our photosynthesis experiment. We were cautious not to choose leaves that were a decaying or had a waxy or fuzzy coating. My group and I chose to use the largest of the freshly picked leaves to use for our experiment because we knew that we would need a total of 24 whole punches. Being able to use the same leaf creates a constant and independent variable for our results and ensures consistency in our data. Our original hypothesis predicted that the breath solution would result in the most leaf disks floating. However, the further we got into our experiment, the more apparent it became that this was not the case. 

    We tested the 12 leaf punches in the breath solution first. After blowing through a straw into the soap and water solution for a minute to create a “breath solution”, we carried out steps 6-13 for the first time. After waiting an appropriate amount of time none of the disks sank, so we repeated steps 6-13 using the same leaf punches. This time all twelve leaves sank, indicating that they are ready to be left under the artificial light. The purpose for carrying out the syringe portion of the procedure is to create a vacuum that will extract the oxygen from the leaves and causing them to sink. By having the leaves start off at the bottom of the solution, the rate of photosynthesis can be measured by the rate at which the leaf punches float. The floating indicates photosynthesis because oxygen gas bubbles, a produce of photosynthesis, is what carries the leaves to the top of the solution. 

  Next we set the “breath solution” with the 12 leaf punches at the bottom of the cup aside and completed steps 4-13 with 12 new leaf punches from the same oak leaf for the sodium bicarbonate solution. All 12 punches sank in under a minute, so the process did not need to be repeated, and was ready to be placed under the artificial light. We placed both solutions with their respective leaf punches under the artificial light. The leaf punched under went a progression before they reached the top. First one side of the leaf disk would float while the other remained on the bottom of the cup. Then in a vertical position the leaf disk would float to the top. One leaf disk floating in the sodium bicarbonate solution compared to no disks floating in the breath solution after 9 minutes indicates that photosynthesis initially occurs faster and easier in the sodium bicarbonate solution. This pattern of more disks floating in the sodium bicarbonate solution than in the breath solution continued at 19min under artificial light with a ratio of 0:2, and at 12-24 hours with a ratio of 0:7. At 42 hours however, both solutions had 0 leaves floating. This most likely due to the fact that the leaves have died from lack of nutrients. If the leaves die than they will no longer produce oxygen bubbles to keep them afloat. 

Although our results did not prove our hypothesis, I now understand why the sodium bicarbonate solution was better suited for a leaf to photosynthesis than the breath solution. Because the three reactants needed for photosynthesis to occur are water, CO2, and sunlight, it can be concluded from this experiment that the sodium bicarbonate when dissolved in water contains more CO2 than the breath solution. Although humans breathe out oxygen, a large amount of bubbles were produced when the water soap solution was blown into. This indicates that most of the carbon dioxide escapes the solution before it came in contact with that leaves.

Possible sources of error for this experiment include the amount of dish soap and sodium bicarbonate used, briefly placing the breath solution under the artificial light before the sodium bicarbonate solution, completing the steps for the sodium bicarbonate solution at a later time than the breath solution, and not consistently monitoring and recording the results of the experiments. 

 

Conclusion

    In this lab my group and I were able to accurately follow the established procedure, and as a result we partially disproved our original hypothesis that the leaf disks exposed to the “breath” treatment will rise to the surface faster than the sodium bicarbonate solution due to the fact that they will be exposed to higher levels of carbon dioxide. This in combination with light, will result in a faster rate of photosynthesis, which will produce higher levels of O2 and cause the leaf disks to float. Our reasoning behind how our experiment would show the rate of photosynthesis was accurate, however it was the sodium bicarbonate solution that resulted in a faster rate of photosynthesis. I now understand that sodium bicarbonate dissolves in water to form Na+, H2O, and CO2. To improve upon this lab I would record the number of leaves floating in the solutions more frequently to maximize accuracy and to fully understand the results of this experiment. Further experiments based off of this lab could include testing how the location of the leaf punch of the original leaf effects it rate of photosynthesis.

Group 2: Gracie, Katie, Ron and Emily

 

AP Biology

Mrs. Cost

7 October 2019

 

Leaf Disk Floatation

 

Purpose

The purpose of this lab experiment is to test and observe how the rate of photosynthesis is affected by different solutions: “breath” treatments and sodium bicarbonate treatment.

 

Hypothesis

I hypothesize that the leaf disks exposed to the “breath” treatment will rise to the surface faster because they will be exposed to higher levels of carbon dioxide, and in combination with light, will result in a faster rate of photosynthesis in comparison to the sodium bicarbonate solution. The faster rate of photosynthesis will produce higher levels of O2, which will then cause the leaf disks to float.

 

Materials

• Healthy, undamaged leaf

• Hole puncher

• Plastic cups

• Water

• Dropper

• Dilute liquid Soap

• Sodium bicarbonate (Baking Soda)

• Straw

• Syringe

• Artificial lighting

• Timer

• Writing utensils & lab notebook

 

Procedure

1. Choose an appropriate leaf for the experiment: a healthy, undamaged leaf with no wax or hair on it.

2. Use a hole puncher to punch 10-12 holes in the leaves. Try to avoid hole punching into large veins in the leaves.

3. To set up the solution, use a dropper to add a drop of liquid soap to two plastic cups filled with water.

4. In one of the solutions, also add a pinch of sodium bicarbonate. Label this solution “Baking Soda”.

5. Perform the “breath” treatment on the control solution (only soap) by using a straw and blowing into the solution for 1 minute. Avoid spilling the solution. Label this solution “Breath”.

6. Remove the plunger from the syringe. Pour 10-12 leaf disks into the barrel of the syringe.

7. Shake the syringe to settle the disks on the bottom (towards the point of the syringe).

8. Push the plunger almost entirely back into the barrel, being careful not to crush the leaf disks.

9. Place the tip of the syringe into one of the solutions, and pull back the plunger until the syringe is about half full.

10. Position the syringe horizontally so the tip of the syringe is pointing up. Tap the side of the syringe to submerge all of the discs into the solution. 

11. Carefully push the plunger in to remove any excess air.

12. Firmly holding a finger over the tip of the syringe, draw back the plunger. There will be suction.

13. Some leaf disks might start to sink once the plunger is pulled back. Repeat steps 6-12 until all of the disks sink in the syringe.

14. If, after 5 repetitions, all of the leaf disks fail to sink, add more soap solution to each of the solutions and try again. 

15. Empty the syringe by removing the plunger from the barrel over the corresponding solution cup. Be sure all of the leaf disks are removed.

16. Place each solution treatment under identical lighting conditions. Be sure to set a timer.

17. Record how many disks rise to the surface and what time they rose to the surface.

 

**We used approximately 3 drops of dilute liquid soap

 

Data

Figure 1: Leaf Disks Prior to Artificial Lighting

Treatment/Sample	# Sank: First Trial	# Sank: Second Trial
“Breath”	0	12
Baking Soda	12	N/A

 

Figure 2: Leaf Disks Under Artificial Lighting

Treatment/Sample	# Floating after 9 min.	# Floating after 19 min.	# Floating after 24 hours	# Floating after 42 hours
“Breath”	0	0	0	0
Baking Soda	1	2	7	0

 

Analysis

In this lab experiment, my group and I selected appropriate leaves to successfully test the rate of photosynthesis of a particular leaf. An appropriate leaf would have no fuzz or wax, and would generally be in good health with no obvious signs of decay. We decided to use a large and healthy oak leaf so we could have enough samples for both treatments. This would also keep the data as consistent as possible since the type of leaf will be the control variable in the experiment.

To begin the experiment, we punched 24 holes out of the same leaf. 12 of these punched-out circles was for the “breath” treatment and the remaining 12 was for the baking soda treatment. Once the leaf disk samples were separated into their respective treatments, we took two plastic cups filled with water and put approximately 3 drops of dilute liquid soap into each cup. We then placed 12 of the disks into a clean syringe and drew up enough of the “breath” treatment to fill approximately half of the syringe. Making sure all of the disks are completely submerged in the solution, we firmly placed a finger over the tip of the syringe and drew back the plunger until all of the disks sank inside the syringe. Once all of the disks sank, we emptied the syringe into the corresponding cup. We repeated these steps with the sodium bicarbonate treatment as well. Once both treatments were done, we placed both treatments under the artificial lighting that was set up in the classroom.

After approximately 9 minutes of being under the artificial lighting, 1 disk in the sodium bicarbonate treatment started to float. At the same time, none of the disks in the “breath” treatment were floating. At the 19 minute mark, another disk started to float in the sodium bicarbonate solution, for a total of 2 leaf disks floating. At the same time, none of the disks in the “breath” solution were floating, again. At the 26 minute and 26 second mark, our group had to stop recording because the class period had ended. The next day, Julie had checked on our group’s samples after being under the artificial lighting for approximately 24 hours. At this time, 7 disks were floating in the sodium bicarbonate solution and 0 were floating in the “breath” solution. The following day, our group checked the treatments again after approximately 42 hours and no disks were floating in either solution. 

Because carbon dioxide, water, and light are required for photosynthesis to occur, I think the reason that the leaf disks in the sodium bicarbonate treatment floated was because they harvested the carbon dioxide from the sodium bicarbonate. The water, carbon dioxide and artificial lighting that was supplied in the sodium bicarbonate treatment proved to be enough to have 7 of the 12 disks float, which means that they were able to perform photosynthesis and produce oxygen gas which caused the disks to float in the sodium bicarbonate solution. The reason the “breath” solution might not have worked as well as the sodium bicarbonate because when we blew air into the solution, bubbles formed, which suggests that when those bubbles popped, the carbon dioxide escaped into the atmosphere, so the leaf disks didn’t have enough carbon dioxide to perform photosynthesis to the extent that it would float to the surface. The bubbles that formed may be because an excess amount of diluted dish soap was added at the beginning of the experiment.

Possible sources of error during our experiment could be the amount of diluted dish soap and baking soda that was put into the two containers of water. Since the video we watched as a basis for the experiment didn’t include precise amounts of water, baking soda, or diluted liquid soap, the correct amount isn’t known. 

 

Conclusion

During this lab experiment, the procedure went well and the directions were followed closely. Considering the purpose of the experiment was to test and observe how the rate of photosynthesis is affected by a “breath” treatment and a sodium bicarbonate treatment, the experiment was a success, as we found that there was a difference in the rate of photosynthesis between the two treatments. However, the data did not support my original hypothesis that the leaf disks in the “breath” treatment would float to the top of the solution first, but the sodium bicarbonate solution floating to the top first. The “breath” treatment didn’t produce any leaf disks that floated, so the data does not support our original hypothesis. To improve this experiment in the future, I would try using varying amounts of diluted dish soap to see if that would change the results of the lab.

Thanks Viviana for stepping in while I was unavailable. I've read many comments that are extremely interesting. I can only backup Viviana's comments.

Emily, you suggested that the position of the leaf disk in the leaf could potentially affect its capacity to float. What led you to this hypothesis? Can you think about an experiment to show it?

I'll check in with him - it can sometimes take a while for mentors to get set up on the site. 

As to the sodium bicarbonate -  that's great that you're thinking about how the leaves might be using it. Does anyone in the group know what chemicals are produced when sodium bicarbonate is dissolved in water?

That's an interesting question about the position of the leaf disk. How do you think being close to the vein could impact photosynthesis? I have some ideas - but I'm curious what you all think. Have you noticed a relationship between position of the leaf disk and whether the leaf floats.

Hello everybody, I am Thomas and I will be your mentor for this session. It is a great pleasure to see that you all have raised up really interesting questions and that you are curious about plant biology. Concerning my background, I graduated my PhD in France quite a couple of years ago and I am now doing a PostDoc in the north of Sweden. My main focus of research is to understand how plants manage to deal with unfavorable conditions such as a lack of light or mineral nutrients. I am looking forward reading from you

Hi Viviana! Our mentor has been added to the group, but he hasn't written on the forum. Does he have access to the platform? Would there be any way to contact him? Thanks!

Hi all! Just wanted to let you know that your group now has a scientist mentor, Thomas. 

Hi! Right now we are waiting for the disks to float under the artificial lighting. At about 7 minutes 10 seconds, one disk in the sodium bicarbonate treatment started to float. At the 19 minutes 45-second mark, another disk in the sodium bicarbonate treatment. Are the disks floating in the sodium bicarbonate treatment because the disks are able to break down the sodium bicarbonate and use carbon dioxide? Also, does the location of the hole matter; more specifically, if the hole is punched closer to a vein, will that cause photosynthesis to happen faster?

Right now we are placing the leaf disks in different solutions, then collecting them back out. Once we get them all out, we place them back into a syringe, and filling the syringe up with water. Pulling the water down and making sure all of the leaf disks float downward in the syringe. When we put the same leaves back in the syringe, they all fell. 

Now, we are setting up the second phase of the experiment. We placed a new set of 12 leaf disks into the syringe with water, and all 12 fell. Next, we placed them all into the baking soda solution. We took both cups, and put them under the light. 

The first trial, in the breath solution, none sank. In the second, baking soda solution, all 12 sank.