Iseult Pigot

LEMNA GIBBA

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My client is the Lemna Gibba. Below is a chronological journal of all the research and experimentations I made in 10 weeks. What started with an experiment on the growth of Lemnas in different canal waters in The Hague evolved into making different tools to measure the growth of this plant.

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Week 1 – A presentation of my client

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Classification

– Genus: Lemna

– Family: Araceae 

– Species: Lemna Gibba 

Known as duckweeds or water lentils

The Lemna Gibba is recognisable from other Lemna because of its round and convex shape, unlike the other species that are flat.

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Where to find them

– In stagnant and slow moving water in Europe, Africa and America

– Forms green mats

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Ideal conditions & reproduction

– Temperature between 6° and 33°

– Lots of sunlight 

– pH between 5 and 7

– Feeds on solar energy (photosynthesis) and nitrates, nitrites

– Reproduction almost exclusively asexual – outgrowths from one end breaks off to form new plant

– Can double their biomass under optimal conditions in 2 or 3 days

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Use in water contamination

When rapidly growing, duckweeds can run out of naturally available nutrients, and begin processing contaminants present in the wastewater to extract nutrients for their sustenance.

Removes diverse pollutants: 

– heavy metals,

– bioremediation of tannery effluent,

– water contaminated by an oil refinery.

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Week 2 – Research questions and the start of the canal water experiments

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The reason I chose the Lemna Gibba as my client is because of its use in cleaning waters from contamination. I want to work with that aspect for the experiment, by collecting waters from different canals around the Hague and seeing how the Lemna grows in the different waters. Ideally I also would need to be able to measure the level of pollution at the beginning of the experiment and at the end, to see how the Lemna Gibba changed it.

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Each container of canal water has one plant in it at the beginning of the experiment. There will also be one with only clean water to compare its growth to the polluted waters. They will all be next to a window and above a radiator to get the optimal conditions for fast growth (warmth and sunlight), and these same conditions will mean that only the quality of the water will affect their growth.

Material needed: containers, pollution measurer.

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Research question: How is the Lemna Gibba affected by the pollution level of different canal waters around the Hague? How could the Lemna Gibba be used for cleaning polluted waters?

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Red circle: canal where I took the original Lemna Gibba plants

Black circles: canals where the different waters come from (to be updated)

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Week 3 – More canal water experiments

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I added three more canal waters, situated on the map and numbered and also in their own container, with one lemna plant each.

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Each container is numbered from left to right, corresponding to the numbers above on the map. 1 is tap water, and 2,3,4 and 5 are canal waters.

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In the last two weeks some of the containers have been doing well, and other have not… Although all the plants are still very small, some have slowly started to multiply (like number 2, that is separating into two plants). Others however have been sinking to the bottom (1) of the container or turning slightly brown (5).

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Closeup of the lemna turning brown for container 5.

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In this container (4), most of the lemnas are multiplying but some on the very left have turned brown/white and have died. It is the container with the most activity and it has only a lot of residue forming and dropping to the bottom, which was not there before.

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Until now I have not been interfering with its growth, as I thought sunlight and warmth would be enough for it to multiply by itself. However I have been doing more research on how to grow lemna, and found that it may be lacking some nitrogen, phosphorus, potash and/or micro nutrients. That can be found in simple things like hummus and/or soil or compost tea, which I may add in the future if this continues.

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Week 4 – Even more canal water experiments and some fertiliser

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This week I decided to experiment more, to hopefully help with the growth of the lemna.

I first went back to the original canal where I found the plants to get some more. Instead of starting with 1 plant, I added some more so that every canal water starts with between 10 or 20. This way, the growing rate should go up, and the chances are higher for some of the plants to survive and thrive.

I also added a lot more containers, 2 per canal water as of now. In one of them, I just have canal water and the lemna. In another, I added some fertiliser to see if it would help with the growth rate. I might also do a third one with a different starting number of lemna to see if that is a parameter that affects the growth.

For the fertiliser, I made my own by using old banana peels to make “banana peel compost tea”. I just put some old banana peels in a jar of water, and let it seep for a week. This contains potassium, phosphorus, calcium and magnesium which should help a lot with the growth!

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I also labeled my containers better, with the canal number and a letter, a being ‘normal’ canal water and b with added fertiliser. I changed the containers to temporary cups so that they are all in the same condition. I intend to have them in better containers (maybe glass jars) once I figure out the best shape/material.

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Week 5 – Making a physical tool to measure the growth

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This week, there has been a lot of growth! Nearly every leaf has duplicated, or even tripled. This means that in a few days, they will separate and there will be twice as many plants in each container. In this first photo you can see a close up of the leaves duplicating.

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Below is the progress for all 12 of the containers. For containers 6a and 6b, the residue is the biggest. It also has the most lemnas turning brown and dying, as the others have very little or even none at all. Its water comes from the most polluted canal.

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The containers 6b (left) and 2a (right) have some interesting activities. 6b (very polluted canal water and fertiliser) has some kind of transparent sticky film forming on the top. And 2a (water from the centre of the Hague and no fertiliser) has a lot of bubbles, signifying a lot of oxygen so a lot of activity from the lemnas.

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The containers 3a and 6a have a few little water insects (very small, only noticeable because they move a lot), probably picked up from the canals. So I will see in the next few days how these containers develop, if it is different from the other containers, therefore if these insects hinder or help with the growth.

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I have also added more fertiliser to all the b containers (on the right). My fertiliser has been brewing for more than a week so it should be filled with nutrients. For the moment, I cannot see a different between the a and b containers, but with the growth rate, I think it should be noticeable quite soon.

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I also starting experiment with a tool that could be used to roughly count how many leaves there are in the jar, so the growth rate could be easy to measure.

For the moment, the tool is an simple square of plexiglass with a design on it. This way, it would be super easy to make yourself. I tried a few different designs to see which one was the best. I think the second one works better, as it cuts the container into smaller areas, and you can roughly count how many squares are filled.

The end result would not be drawn on like this though, but scratched into the plexiglass so that the whole square remains transparent.

I also have another idea, that would be more precise and also only digital. It would some kind of device or app where you can take a picture of your container and it would tell you the percentage of green inside the circle. This way, you get a very precise result that would be much easier to compare to a previous result than with the object above. I found a website where you can upload a picture and it will give you a colour palette and the percentages of each colour.

The two green colours added together make around 0,26 for the first picture and 0,28 for the second. This is not very precise though but a nice tool to experiment with.

I am also looking at a way to code this.

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Week 6 – A prototype of the measuring tool

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In the past week, the leaves have continued to multiply and this time most pf the plants have about 4 leaves, so twice as much as last week.

The amount of growth between the containers with and without the fertiliser still about the same.

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I started making the measuring tools from the prototypes I made last week. I am using plexiglass and will cut and engrave them using a laser cutter.

For the design, I thought the prototype that worked the best was the second one with a grid. So I drew another one for the final tool, and also two others, still with the grid idea but with different shapes. I also added a handle so it is easier to use.

The red parts will be cut and the blue engraved. The engraving will be very thin and as the whole instrument is transparent, the totality of the plants will be visible whilst still being able to count them using the grid.

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Week 7 – The final physical measuring tool and the start of a digital one

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This week growth continued around the same rate. The plants with four leaves have started to separate in two.

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I continued to work on both the physical and digital measuring tools. For the physical, I laser cut the designs I made last week and tested them on my containers!

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I also worked on the code for the digital measurer. My initial idea was to count the number of green pixels in an image of the containers. However I could not find a way to include all shades of green without doing it manually, and the counter kept giving me 0 pixels as the primary RGB green was not present in the image. So I decided to try a different approach and modify my image so that it would transform into only being black or white pixels depending on the initial colour of the pixel. As my containers are white and the plants dark green, the plants became black and the background disappeared, leaving me with an image like the one below.

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Once the image is transformed, the rest of the code is a pixel counter for the black pixels. It is then displayed as well as the percentage of black of the image. The full code is below.

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And these are the results for 3 different images with a growing number of lemnas!

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The code works quite well, but I do think some adjustments can be done so it is more precise, and I would also like to work on the design of it. The only thing I am unsure of is its accessibility, it is not easy to use as I need to manually change the line of code with the image link when I want to measurer another image.

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Week 8 – The finalised digital measuring tool

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The growth from the last week!

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I continued to work on the digital measuring tool. I added a bit to calculate the number of leaves. I did this by counting the leaves myself on a few pictures and comparing it with the number of black pixels, to get an approximate of the number of black pixels that form a leaf. I am going by leaf and not by plant as a plant can contain between 1 and 4 leaves and can vary in size a lot more.

I also compiled all the data from 4 weeks of growth from all 12 containers to make a kind of black and white photo timeline, with all the data to see how much the lemnas grew. They are in order from the first container to the twelfth, and each line is also in order of time from left to right.

I think this way is a lot more clear with the numbers, and is visually a lot more interesting.

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Week 9 – The final project

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Measuring the growth of the lemna gibba in canal waters of The Hague

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My client is the lemna gibba, a plant found in stagnant waters like canals. It has the ability to absorb pollution and this particularity was the basis of my experiments. During several weeks, I measured the growth of the lemna gibba in different canal waters from around The Hague, which lead me to create tools to facilitate the measuring.

My final project consists of two measuring tools, one physical and one digital, made for the lemna gibba.

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Visual timeline of the growth

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Physical lemna measurer

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Digital lemna measurer – how it works

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Digital lemna measurer – visual interface

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Iseult Pigot