wmacostfall2019 project 4

Project by group wmacostfall2019

Info

Explore Work on this next!
What do we know about plants from our experiences outside of school? What have we discovered in class and background research? What questions about plants interest us?
Research Question What do we want to test or study? How did we come up with the question(s). How does the question fit what we know about the topic?
Predictions What are the possible outcomes of our study given the variables we are working with? What is our explanation for why and how we think this will happen?
Experimental Design What is our plan? Be sure to include enough detail that another group can replicate our experiment. What variables will we test? What variables will we measure and observe? What variables will we keep constant? How will we record our data?
Conclusion What claim can we make from our experiment? What are possible explanations for our results? How do the data we collected and our reasoning with scientific ideas support our claim? What future experiments could be done to expand on the results of this experiment?

Updates

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.
PlantingScience Staff
has been updated by administrator
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.
Viviana June
said

So, it looks like the fertilizer was toxic, even at 11 drops! Even if this wasn't the result you're expecting, it's actually a very informative experiment. I haven't observed fertilizer toxicity that stops seed germination yet - so this was actually a novel result for me! I had to actually look up how fertilizer can cause seed death as it wasn't something I had not really heard of before. Typically, putting too much fertilizer on plants causes what farmers call "burn". It's called burn because the plant will develop yellow and dry spots, which can also happen if the plants are overheated. These spots are where the plant has dried out, and they dry out because of the high salt levels in fertilizer (the nitrogen, phosphorus and potassium are typically added to fertilizers as salts). Often the worst ions for this are urea and ammonium nitrate salts, which are added to give the fertilizer nitrogen. The high salt concentration will often kill the seed/prevent it from germinating. Do all you have any ideas how high salts would kill the seed/germinating plant?

Also, what might be useful in drawing a conclusion is to actually dig out the seeds that didn't grow. It could be interesting to see if they germinated at all (where you see a small plant emerging from the seed that then died) or if there was absolutely no germination. Considering Ragene said there was a bit of green that poked out of the 11 drop soil last week, I think you might see a difference between the seeds you dig out.

Ragene
said

We are reaching the end of the experiment. Only the non-fertilizer plant continued to grow. Could you tell us why the excess amount of fertilizer negatively affected the plants?

Viviana June
said

This is interesting! I'm curious to see if there is anymore growth in the 11 drop pot - but it does look like you're getting some interesting results!

As to whether 11 drops was too much: this is very dependent on how concentrated your fertilizer is. For reference, I use a solid fertilizer that you use by dissolving it into water when I'm growing plants, and I typically dissolve 4g of the fertilizer into 2 gallons of water, which waters between 60 pots (the 4g/2Gal is the recommended concentration listed on the container). So, the amount of fertilizer to use can be really very low! It's hard to say whether 11 drops is definitely too much without a concentration, but it does sound like it could be negatively impacting growth.

Ragene
said

The same pattern continued. Only the pot without fertilizer grew. The individual size of the pot is similar to an ice cream cone. We put in 11 drops in one and 33 drops in the other, expecting only the 33 drop to harm the growth. I saw a little bit of green poking out from the 11 drop soil a few days ago, but as the soil shifts, it was buried again.

Viviana June
said

It's been great to get the updates on the plants! Have you all seen any more growth since Wednesday? You've all mentioned that you think that the fertilizer could be negatively impacting growth, and I can actually think of some reasons why that happened - but I'm curious as to whether any of you have any ideas about what in fertilizer could negatively affect growth. 

Also, I'm curious as to what size pot you're using - this could be making the fertilizer amount you added more or less concentrated in the soil, which could affect the seedling growth. This might be useful in terms of figuring out what's going on with these results!

 

Lauren
said

When we checked our plants today, a new plant sprouted in the other well with no fertilizer. As of now, only the plants in the section with no fertilizer are growing.

Ragene
said

Only the seeds in the non fertilizer pot have grown. Also, when watering the pot, the fertilized pots seem to absorb water much quicker than the non fertilizer pot. I think we need to examine the fertilizer to make sure there were no errors.

Zoe
said

Today in the lab we only observed the change in the non fertilized pot. The other two remained the same. 

Is it possible that adding too much fertilizer may affect or actually cause damage to the seeds? 

Saki
said

We only see the growth from non fertilizer pot. We did not see any change from the other pots. We added the water the way you shows us before(bottom watering).  

Lauren
said

When we checked on our plants today there was more growth in one of the wells with no fertilizer, and in that section there are two plants that have sprouted. Other than those two, there has been no growth in any of the other wells in the container.

    Viviana June
    said

    It could be that the seeds are a little slow to sprout - just make sure all of your pots are well waterered. It could also be that the fertilizer is affecting the sprouting - difficult to tell at this point!

Saki
said

Surprisingly, the one without fertilizer starts to grow, but we did not see any changes from other two pods. This is opposite from what we expected. We thought plant with fertilizer will grow more. What could it be the reason for that? I personally think the fertilizer gets poison for plant somehow. 

    Viviana June
    said

    It's possible the fertilizer has affected the plants, but it's less common for the fertilizer to affect germination of seeds.

PlantingScience Staff
joined the project
Lauren
said

Today when we checked our plants only one of the radish seeds had grown and it was in the cup with no fertilizer. No other seeds have sprouted since we last checked them on Friday. 

Viviana June
uploaded covering_pots.jpg in project files
    Viviana June
    said

    This is a good way to cover your pots to help keep the soil moist.

Viviana June
said

If the top of the soil is dry after 2 days, I'd really make sure to get the soil well watered without really worrying about over watering it. Usually I find that my soil doesn't dry out as quickly, but so many factors (type of soil, temperature, humidity, pot size) can affect this that it can be hard to predict how frequently you'll need to water. I have actually seen seeds germinate in water, so I wouldn't worry too much about over watering the soil! It's really more of an issue with plant growth long term. Another thing you can try to keep the soil most is to loosely put a covering of cling film over the pots (make sure it is loose - don't seal the pots tightly!). This reduces water evaporation from the soil surface. I usually put a plastic lids over my pots when I'm trying to germinate seeds. Just make sure to remove the covering once you see the plant emerge from the seed.

Ragene
said

It has been three days since planting the seeds, and we do not see anything so far. Looking back, we have not accurately measured the depth of which the seeds are planted. I hope the depth is adequate for the seeds to sprout. The soil was dry before we watered them. The top soil was dry, but there are relatively large stones which may explain the dry soil.

Lauren
said

There is no change in the plants, and we added some water today.

Viviana June
said

Hi all - I've seen a few posts asking about how much to water plants. This is a really great question, and is actually a pretty tricky part of growing plants - in my time growing plants in the lab, I have definitely over- and under- watered my plants, and have learnt a lot about what the correct amount of soil moisture looks like from experience. My best tip from years of growing plants is to use the bottom watering method, where water is added to the dish you put the pots in, this is left for about 10 minutes, and then the excess water is discarded. I've put a diagram in the "Files" section of this page, and would recommend you have a quick look at that. I find that if you're bottom watering the plant, the soil ends up at nearly the perfect moisture level every time! Let me know if you have issues finding the diagram. Also, feel free to add pictures of the soil to the Files section, and I can try and see if it looks too moist/too dry. I don't think that fertilizer being washed out will be too big of an issue given this is a short running experiment (if you were going to grow the plants for over a month, then I'd suggest more fertilizer). Bottom watering will also help avoid fertilizer runoff.

    Zoe
    said

    Got it! Thank you so much!

Saki
said

We added same amount of water into the pots today. There is no changes for all six pots. 

Zoe
said

We put seeds into 6 different pots and added water on the first day and the second day. We set up 2 pots for no fertilizer, 2 pots for a regular amount of fertilizer, and the last 2 for more fertilizer. We did not observe any changes in the plants so far. Is it necessary to add water every day? I was worried that too much water might damage the seeds. Also, because we are using liquid fertilizer, we are wondering if the effect of the fertilizer might change if we keep adding water to the soil.  

    Viviana June
    said

    Long explanation: watering everyday probably isn't necessary, but how frequently you'll need to water depends on how dry/hot the place you're growing the plants is. Soil for seed germination needs to remain moist, otherwise the seeds won't germinate. However, too much water can be bad as well. General advice is you want moist soil - this usually looks dark brown, but will leave some water on your hands if you squish the soil between your fingers (like a small film of water, not like squishing a wet sponge). Overly wet soil might have pools of water, or feel muddy. Soil that is too dry becomes light brown, and it is way too dry if it gets crunchy/crispy. I'm sorry this is such a long explanation on identifying soil - it's really hard to describe the ideal wetness that the soil should have - the best way to identify it is by feeling the soil.

    My advice for the easiest way to keep your plants well watered without over watering is to use a method known as bottom watering. I've put a diagram on how to bottom water plants in the Files section of this page (see the panel on the left). Bottom watering prevents over watering (the soil will only take up as much water as it needs from the dish, as long as you discard the water in the dish after 10-20 mins). It will also be less likely to wash out fertilizer from your pots (if you add too much water to the soil, it eventually flows out of the bottom of the pot and can carry nutrients with it).  I would probably not worry too much about fertilizer run off, as this is a short experiment - I would worry more if this was a month long growth experiment. I find in the lab one fertilizer application is enough for seedlings.

    Short summary: Watering everyday is probably too frequent, every 2-3 days should be enough, but I can't know for sure as I haven't seen the soil. Bottom watering is the best method to get the correct amount of water into the soil, and will prevent fertilizer from washing out. There's a diagram of how to bottom water in the Files section of this page (in left hand column)

Viviana June
uploaded How_to_bottom_water.jpg in project files
Saki
said

We put the seeds into the pot. Since we have 6 different pots, we did the lab twice. I think that will lead us to have more credible results. This morning, we checked the plants. I could not see any changes. I am just wondering the differences between liquid and solid fertilizer. Also, how often we should put wanter in it. If we put too much water, the fertilizer will be weaker. However, if we don't put water, I think the plant won't be able to grow. 

    Viviana June
    said

    That's great you could do two pots per treatment! Good question about watering plants! This is true, watering can rinse out fertilizer, to an extent, but it shouldn't be an issue. Generally, when you're germinating seeds, you want moist soil, but not wet. Seeds need to take up water to germinate properly, so if it gets too dry, you might run into an issue.  The best way to avoid over-watering is to water the plants from the bottom of the pot - so, if your pots are sitting in a tray/dish , add water to the bottom of the dish, and wait about 10 mins for the soil to take up the water. Then, pour the remaining water out of the tray/dish. Make sure to check up on the plants frequently to make sure the soil is still moist - how often you have to water depends on the size of your pots/humidity/temperature/type and age of the plant you're watering. 

     

    Solid v. liquid fertilizer:

    Solid granules - these you mix into soil, not water. They sit in the soil and release nutrients over time. You don't need to reapply as much, and the amount of nutrients the plants can take up is affected as the nutrients aren't evenly distributed through soil as other types.

    Liquid fertilizer (and solids that you dissolve into water to form a liquid that you add to plants): These add a more even blend of nutrients throughout the soil. They typically need to be reapplied more often as they don't sit in the soil slowly releasing nutrients, like granules do.

    I wouldn't worry about reapplying over the course of your experiment even though you've used liquid - one application is enough for seedlings.

    Viviana June
    said

    Also: typically I water my plants when the soil is starting to dry out. Given that these are seeds you're trying to germinate, you'll want to be sure the soil is moist, so I would guess you'll need to add some water every 2-3 days. However, this is very location dependent! If they are looking dry, water more frequently, if they are looking overly moist (a sign of this is green algae or white fluffy fungus on the top of the soil), cut back on the water. Just make sure the pots aren't sitting in trays/dishes with water - that should be drained off after each watering.

    Viviana June
    said

    Short summary of watering as I know that was kind of a long answer:

    1) Keep the soil moist and don't let it dry out - I wouldn't worry about the water washing out the fertilizer in this experiment.

    2) Make sure there isn't water sitting in the tray/dish the pots are in - that's typically how they end up over-watered.

Viviana June
said

I've replied to a few specific questions on the comments. Some general comments -  a number of you have stated that you think the fertilizer will affect growth. How do you think it will affect growth? Why do you think that the growth will be affected by the fertilizer?

Also, with fertilizers, they typically have a variety of nutrients necessary for plant growth. However, all fertilizers have compounds that have the elements nitrogen (N), phosphorus (in phosphate) (P) and potassium (K). Fertilizers will have these in different ratios, which is known as the NPK number, and most fertilizers, even if they don't list ingredients, will have the NPK number displayed on them - for example, this fertilizer  https://www.flinnsci.com/fertilizer-all-purpose-liquid-32-oz/fb0676/ has an NPK number of 10-15-10. This means that by weight, 10% of the fertilizer is N, 15% is P (in the form of P2O5), and 10% is K (in the form of K2O). The remaining 65% is inert ingredients/other minerals. If you can find the NPK number, great! If not, no problem! The most important nutrients to think about when thinking about your experiment will be nitrogen, phosphorus, and potassium, so even if we don't know the exact ingredients, we can think about how those three could affect the plants.

It would also be great to take photos of the plants in addition to weighing them - I suspect photos will help interpret the results.

Just out of interest, where are you growing your plants? 

I look forward to hearing about the results!

Ragene
said

We have prepared the pots and are waiting for the seeds to sprout. It took three days for the seeds to sprout for the previous experiment, so we don't expect to see anything this week. We gave 10mL of water for each pot. We could not determine the chemical composition of the fertilizer since it does not have information on the label, and the fertilizer is from Flinn, and is not commercially sold. The soil we used seem to have large grains of dirt, it may be a chunk of dry dirt, or a stone. We hope the masses do not interfere with the sprouts. We will be back on the experiment Friday.

    Viviana June
    said

    Usually the plants do pretty well even if there are chucks in the soil - I often find small twigs in the soil we use in the lab and it doesn't seem to affect their growth.

Lauren
said

Yesterday, we finished setting up our experiment and put the appropriate amount of fertilizer in each sample. Once the experiment was completely set up, we added about 10mL of water to each well, and placed it under the artificial light in our classroom. We checked on our plants today in class, but we will not be back in this class until Friday, so we will not be able to monitor the plants Thursday. 

 

Ragene
said

The lab we were planning has started yesterday, and we are preparing our pots and starting our seeds. We have decided to use the liquid fertilizer, and three tests: no fertilizer, 1g fertilizer, and 3g fertilizer. We have two pots per test, and three seeds per pot.

Lauren
said

Today in class we started our experiment with the fertilizer. We split the container that was given to us into three different sections, and each section has two spots for our plants. We are testing whether or not the amount of fertilizer that is give to a plant will impact how quickly the plants will grown. In the first section, the seeds will not have any fertilizer given to them. The second section will only be given 1.1g of fertilizer, and the third section will be given 3.3 g of fertilizer. We only added fertilizer to the second section, but we will finish everything else tomorrow. 

Saki
said

Due to the power down and long weekend, our final lab delay, but we finally started it today. We use liquid fertilizer. Unfortunately, I could not find information of component of fertilizer. We decided to put three seeds into each pot. We will put all of the pots under the light and keep giving save amount of water. We will only change the amount of the fertilizer. I think amount of fertilizer will effect the growth speed of the plant and strength of plant. 

Zoe
said

We started the fertilizer experiment in class and what we are looking for is how does the amount of fertilizer can affect the growth of plants. We set up 3 containers that have different amounts of fertilizer, so we can compare the outcomes. We are using liquid fertilizer for this experiment. For container 1 we are going to put no fertilizer in it, we put a regular amount(about 11 drops?) amount of fertilizer in the container 2, and for container 3 we are going to triple the amount of fertilizer in container 2 and put it into the soil. 

Ragene
said

Instead of the fertilizer lab, we started a different lab by using radish seeds in order to figure out how plants gain mass. In order to find out, we created three cases. Dish one has seeds with water and lights, dish two has seeds with water, and dish three has seeds with light.

Data:

#1

Dish - 3.32g

Dish w/ seeds - 3.67g (seeds - 0.35g)

#2

Dish - 3.32g

Dish w/ seeds - 3.67g (seeds - 0.38g)

#3

Dish - 3.32g

Dish w/ seeds - 3.85g (seeds - 0.53g)

Viviana June
said

Also, once you get more of your experiment planned for the fertilizer experiment, if you post it here, I can give you all feedback on it before starting the experiment. It sounds like it should be an interesting experiment!

Viviana June
said

The radish experiment sounds interesting - I'll be interested to hear what results you get!

Zoe
said

In the new lab there we are doing right now in class, we need to find out where do plants gain their mass, the possible answers now included nutrients that plants absorb, the growth of plant cells, or the amount of water they absorbed. We used radish seeds and put them into different environments in order to observe what variable might affect the mass of the seeds.  

We create 3 different conditions:

Dish #1 with lights and water 

Dish#2 with only water

Dish #3 with only lights

 

Data: 

Dish #1(water and light)

Dish: 3.32g

Dish with seeds: 3.67g

Seeds: 0.35g

 

Dish #2(only water)

Dish: 3.32g

Dish with seeds: 3.70g

Seeds: 0.38g

 

Dish #3(only light)

Dish: 3.32g

Dish with seeds: 3.85g

Seeds: 0.53g

 

 

 

Saki
said

Other than the lab we were talking about, we started new lab by using radish seeds in order to figure out where plants get their mass. We created three different conditions. Dish one is seeds with water and lights, dish two is seeds with water, and dish three is seeds with light. We put all of the dishes into the ziplocks and close them. 

#1

Dish 3.32g

Dish +seeds 3.67g

Seeds 0.34g

Dish +seeds+water 3.34

#2

Dish 3.32g

Dish+seeds 3.70g

seeds 0.38g

Dish +seeds+water 3.38

#3

Dish 3.32g

Dish+seeds 3.85g

seeds 0.53g

 

Lauren
said

In the new lab we are doing in class, we are testing how the growth of radish seeds is impacted by its environment. We are testing this by changing the conditions in which we put the samples of radish seeds, and measuring their growth over a two week period. Today, we sectioned off the seeds into three dishes, measured the amount of seeds, and placed them into their designated conditions. The first sample will have water and be placed under a light source, and the other two will only be exposed to either light or water. 

 

Sample Measurements:

 

Sample #1 (Light and water): 

  • Container Mass: 3.32g

    • Container mass with seeds: 3.67g

    • Seed mass: 0.35g

Sample #2 (No light and water):

  • Container Mass: 3.32g

    • Container mass with seeds: 3.70g

    • Seed mass: 0.38g

Sample #3 (Light and no water):

  • Container Mass: 3.32g

    • Container mass with seeds: 3.85g

    • Seed mass: 0.53g

Viviana June
said

One other thing - think about how many plants per pot, and how many pots per fertilizer amount you want to look at for the fertilizer experiment. Multiple replicates are important for good data! I'm not sure how big the pots are that you're planning to use - generally I'd say no more than 2-3 seeds per pot is a good starting point.

Ragene
said

Analysis:

After 24 hours of being submerged under breath and baking soda cup, eight disks from the baking soda floated to the surface of the water while the disks from the breath cup remained the same. After 48 hours, all of the disks floating sank. This somewhat supports our hypothesis since it is evident that photosynthesis took place in the baking soda cup.

Conclusion:

The leaf disks floated to the surface of the cup by absorbing CO2 from the solution. The disks then fell because it no longer was capable to photosynthesize. Possible source of error is the lack of observation. There were no observed floating disk from the breath cup. However, it is reasonable to think that it rose and fell during the night. A camera programmed to take a picture at a given interval could solve the problem.

    Viviana June
    said

    I think that's a good point that because you weren't observing the cups at all times, it's possible you could have missed the leaves in the breath cup floating.The camera idea is great! I've done that for experiments that need to go on overnight in the lab so that I can see what happened when I wasn't there. However, the leaves in the baking soda cup appear to have floated more (enough that you could observe it) - why do you think they floated more?

     

    Also, you've said that leaves float to the surface of the cup by absorbing CO2 from the solution. You've also mentioned that photosynthesis is important for floating. What do you think about what happens during photosynthesis that allows the plant to float?

Ragene
said

50 mL beaker

fertilizer (liquid)

pipet

soil

lighting

water

electric scale

container

seeds

 

    Viviana June
    said

    This looks like a pretty complete ingredients list for the experiment Saki has suggested about studying how fertilizer affects growth. Do you know which fertilizer you plan to use?

Saki
said

For next lab, I want to test how the fertilizer can affect the plant growth.

We can create three different amount of fertilize with solids, and observe any relationship between amount of fertilize and growth. 

I want to know putting tons of fertilize can actually grow plant more than plant with less fertilize. 

    Viviana June
    said

    That is an interesting question to test! I have a few questions/points you might want to think about as you plan the lab.

    1. What amounts of fertilizer would you try, and which fertilizer would you use? Using too much for all three amounts, or too little might mean it is difficult to see differences between the amounts.

    2. What would your control be?

    3. What other variables could affect plant growth, and how will you control them?

    4. How are you going to measure plant growth? There are many different ways to do this, with the most common being height or weight.

    5. Fertilizers usually have a few different elements in them that affect plant growth in different ways - the standard key elements in a fertilizer are nitrogen, phosphorus and potassium, as they are important for plant growth. Some might have other minerals that plants use as well. How might the different elements impact plant growth as you use more fertilizer?

Saki
said

Also, based on the data, we can know that photosynthesis will take time to create enough oxygen to flow the leaf discs up. If we can measure the amount of oxygen and carbon dioxide occurred every hour during this lab, we could be able to find the speed of photosynthesis. By figuring out of this, we can know the reason for those discs which float once but sank. It can be because leaf discs are not healthy for day 3, or leaf discs used every CO2 in the solution so that leaf discs cannot photosynthesis.  

    Viviana June
    said

    I think that you're probably right in that either the CO2 is used up or the leaves aren't healthy enough on day 3 to photosynthesize and float. Trying to measure the rate of photosynthesis would be a great way to test this! Could you think of a method that could be used to measure the concentration of CO2 in the water, or the O2 that is released?

Lauren
said

Analysis: 

In this lab, my partners and I studied the process of photosynthesis, and the rate in which photosynthesis occurs. In order to properly conduct this lab we had to select a proper leaf, which was not too waxy or fuzzy, and showed no signs of decay. We chose a large leaf found on campus; however, we do not know what type of leaf it was. Once we selected a leaf, we punched 24 holes and designated twelve for the baking soda treatment, and twelve for the “breath” treatment. 

To prepare our solutions, we added a few drops of soap into each cup of water. Once the soap was added, we proceed to add the baking soda and the “breath” to their proper cups. After this, we places twelve of the leaf disks into a clean syringe, and filled the syringe a third of the way full with the baking soda solution. We then placed a finger on top of the tip of the syringe and pulled back on the plunger of the syringe in order to make all of the leaf disks inside sink to the bottom. When all of the leaf disks had sunk to the bottom of the syringe, we placed the disks into their designated cup and repeated this for the disks in the “breath” solution. After both sets of leaf disks were placed into their cups, they were placed under an artificial light source and monitored throughout the class.

During class time, all of the disks in both cups remained at the bottom of the solution, and none of them rose to the top until approximately 24 hours after being placed under the light. The cup with the baking soda had 8/12 leaf disks float to the top, while the cup with the “breath” solution had no leaf disks float at all. After 48 hours, all of the lead disks had sank back to the bottom and there were no more floating on the surface of their solutions. 

Some possible sources of error during this lab include the amount of substances added to either of the solutions. For example, we did not measure the exact amount of soap and water we placed into both cups. We also did not measure the amount of baking soda that went into the baking soda cup. This is because we were told to place a “few drops” of soap into both solutions, and only a  “pinch” of baking soda. While these may give us an estimate for how much of each substance we should place into the cup, it is not exact and one cup may have more of one thing than another. Another possible source of error is that we used tap water instead of distilled water. While, this may not have altered the experiment too much, there is a chance that any excess substances that are in the tap water could have impacted the results slightly. 

 

Conclusion:

The results of this experiment do support our hypothesis that the leaf disks in the “breath” solution will not float to the top of the solution. This is because the leaf disks in the baking soda (NaHCO3) solution used the CO2 from the baking soda dissolved in the soap-water solution, in order to photosynthesize, and the O2  given off by the leaf disks allowed for them to float towards the surface of their solution. On the other hand, the leaves in the “breath” solution may have not had enough CO2 available to perform photosynthesis. Instead, the CO2 that was present in the solution may have “escaped” because we had let the solution sit for a while before adding the leaf disks in. The lack of CO2 is what did not allow for the disks to float to the surface. 

To ensure the experiment is more accurate, we should accurately measure the amount of substance that is in the experiment: the water, diluted soap, and the baking soda, should be measured either using instruments like a graduated cylinders and measuring cups, or they could be measured in grams on a scale. By measuring the amounts of these solutions, we are able to achieve more accurate results for this experiment.

    Viviana June
    said

    I like that you're thinking about potential sources of error, and I definitely agree that variations in measurements could have affected the outcomes. Could there have been any variation in the leaf disks? I find that biological variation is often an important contributor to variation in my results - I often grow genetically identical plants in the exact same environment but still see some differences between them! I do think that taking them from the same leave was a good idea - it should reduce that variation a little. I also think you're probably correct about the breath solution v. baking soda - I suspect there is more CO2 in the baking soda solution, and if there wasn't quite enough in the breath solution the leaves may not have been able to photosynthesize.

    One question I have for you - why do the leaves sink when filled with the baking soda solution (which contains CO2), but rise when releasing O2? Is there any difference between CO2 and O2 that could explain this? Also, why do you think all disks sunk after 48h?

Zoe
said

Analysis:  There was oxygen in the leaves' cells because of the photosynthesis and oxygen is less dense than the water, which means that when the plant cell contains oxygen, they should float on top of the water surface. But we did use the syringe to create a vacuum and compressed the oxygen out from the leaves, and that's why they sank to the bottom of the cup. 

There was oxygen in the leaves' cells because of the photosynthesis and oxygen is less dense than the water, which means that when the plant cell contains oxygen, they should float on top of the water surface. But we did use the syringe to create a vacuum and compressed the oxygen out from the leaves, and that's why they sank to the bottom of the cup. 

In the second part of the lab, when leaves were settled under the light they started photosynthesis again, which absorbs light energy, synthesizes carbon dioxide and water into energy-rich organic matter, and releases oxygen. During the lab, the lamp provides light energy, and the baking soda releases carbon dioxide, allowing the leaves to photosynthesize in the water. When the plant cells were refilled with oxygen, the leaves floated again. In another cup that did not contain baking soda, the condition did not allow the leaves to fully process photosynthesis because there was no baking soda in there. The leaves in the breath cup did not have enough oxygen to float and that's why they stayed sink in that cup. 

In the third part of the lab,  when leaves were settled in a place that has no light, they sank to the bottom of the cup on the next day. The possible explanation for this is that oxygen was slowly diffused out from the plant cell due to the fact that they are nonpolar and hydrophobic molecules that can pass through the plasma membrane easily without using any energy. When enough amount of oxygen went out from the cell, the leaves would sink because of the increased weight. Moreover, the reason why that these leaves didn't float back up is that they were in the environment with no light, the plant cells couldn't process photosynthesis, and they certainly could not take in oxygen molecules to make themselves float again, and that's why there were no leaves floating on Day 3.

(Please feel free to add more or correct me! I think I am missing some details. )

 

 

 

    Viviana June
    said

    Interesting analysis! The leaf performing photosynthesis is definitely important to it floating.

    However, I did want to clear up why the disks sink. So, leaves have pockets of air -a mix of gases not just oxygen- between cells - particularly between cells in the spongy mesophyll layer (see https://en.wikipedia.org/wiki/File:Leaf_Tissue_Structure.svg). When you put the leaves in the syringe with water and pull the plunger back, you're creating a vacuum - this pulls air out from the leaf (eg, from between the cells in the spongy mesophyll layer). When you release the vacuum by releasing the plunger, the solution in the syringe (so breath solution or baking soda solution) will enter the leaf and fill the spaces that used to be filled by air. This allows the leaf to sink. From reading your answer I couldn't quite tell if this is what you meant - so I just wanted to put the explanation in just to make sure there were no misconceptions! But you're right in that density matters - the pockets of air are less dense than pockets of water, and this is why the leaves initially float and then sink.

    One question you haven't quite answered: both carbon dioxide and oxygen can be gases (eg we breathe in oxygen as a gas, and breathe out carbon dioxide as a gas). The baking soda releases CO2 into the water, which the leaves use in photosynthesis, producing O2. Why do the leaves sink even when filled with baking soda solution (which has CO2), but rise again once they release O2? Is there a difference between CO2 and O2 that could explain this?

Viviana June
said

Great! I'm so excited to hear the results you've gotten so far from the floating disk experiment. Have you all thought about why some of the leaves float/why others sink?

Saki
said

Day 2

Baking soda cup: 8 floating 

Breath cup: No change 

Day 3 

Baking soda cup: 0 floating 

breath cup: No change 

 

Viviana June
said

Hi all! Just wanted to let you know that we've got mentors assigned to all the groups, and I am now this group's scientist mentor. 

Saki
said

We are currently working on a lab involving Leaf Disk Flotation. We created two different conditions of cups. One has water, soap, and baking soda. The other has water, soap, and CO2. We use a syringe with leaves inside to create vacuum, so that all the leaves will sink when we put them into cups. There were ten leaf discs in each syringe. Once we put the leaf discs into their cups, we placed them under a light source and checked in on them in five minuet increments.

5 mins: No change in either cup

10 mins: No change in either cup 

15 mins: No change in either cup

20 mins: No change in either cup

25 min: No change in either cup

 

 

Viviana June
said

Hi everyone! My name is Viviana and I am the classroom's scientist liason. I am going to be talking to you all until the mentors get assigned to projects. I did my undergraduate degree in biochemistry at the University of Cambridge in the UK and I am currently doing my doctorate degree in cell and molecular biology at the University of Texas at Austin. I study why hybrid plants are larger than their parents. Hybrids are organisms that result from crossing two different species together - such as the liger, which is the offspring of a lion and a tiger. Hybrid organisms grow larger than their parents do, and so farmers and plant breeders use hybrid plants to get higher yields from crops. Scientists still don't really understand why hybrids are larger than their parents, and I'm trying to learn about the genes that might be involved in helping hybrids grow.

When I'm not in the lab, I enjoy figure skating and playing with my two cats, Mika and Cowboy.

I've read through your replies - I love the questions you all are asking about plants! They're interesting questions and hopefully we can learn about them over the course of this project. 

Saki - great question! One way to observe plants is to study seedlings - it only takes about a week to get a seedling from good seeds. I perform a lot of experiments on seedlings in the lab for this reason!. We can also take samples from older plants (eg, taking leaves from trees) and then performing experiments using those samples.