We use cookies to give you the best experience possible. By continuing we’ll assume you’re on board with our cookie policy

See Pricing

What's Your Topic?

Hire a Professional Writer Now

The input space is limited by 250 symbols

What's Your Deadline?

Choose 3 Hours or More.
Back
2/4 steps

How Many Pages?

Back
3/4 steps

Sign Up and See Pricing

"You must agree to out terms of services and privacy policy"
Back
Get Offer

Effect of nitrate concentration on the growth of Duckweeds

Hire a Professional Writer Now

The input space is limited by 250 symbols

Deadline:2 days left
"You must agree to out terms of services and privacy policy"
Write my paper

At the beginning of the experiment, I put on a lab coat to protect myself from any danger that may occur. I made sure that all my equipments were clean and dry before I started, and I also measured the temperature of the room to confirm it was around room temperature. I then made sure that the ice cube tray was clean, I put a little label on one end of the tray to indicate my starting point row of the ice cube tray.

I then made a little note to myself that the label indicated the row which will contain the 0.0% x 10-3 concentration of nitrate in the solution, and the rows onwards will contain the concentration of nitrogen in solution in ascending orders which I will use (0.0, 0.4, 0.8, 1.2, 1.6 and 2.4 % x 10-3). I

Don't use plagiarized sources. Get Your Custom Essay on
Effect of nitrate concentration on the growth of Duckweeds
Just from $13,9/Page
Get custom paper

Whilst pouring the solutions into a glass beaker I put on goggles and gloves to protect my eyes and hands from any contacts with the ammonium nitrate solution, as any contact can lead to irritation of the skin and eye.

I poured 80-90cm3 of the 1st concentration which contained 0.0% x 10-3 of nitrate into a 100cm3 glass beaker. Next I used a clean syringe to measure out 25cm3 of the solution into the 1st well (near my label). The tray had 3 wells in a row and there were 6 rows, I repeatedly added 25 cm3 of the same ammonium nitrate solution into the remaining two wells of that row, so that I will obtain a result of three replicates with each concentration.

Using the replicates will give me a more reliable average result, and it will enable me to use more advanced statistical tests, as the class results will be pooled to generate sufficient data. I pored 80-90cm3 of each solution into the glass beaker, to ensure that there was enough for the other two replicate. As I repeated the process for all the other 5 concentrations of nitrate in solutions, each time when I used different concentrations of nitrates I made sure that I washed out and dried the beaker and the syringe, to avoid any contamination of the solutions as this would lead to the concentration of nitrogen and other nutrients to change, therefore affect the outcome of the results. Each time I used a syringe that had accuracy of + – 0.1cm3 , as it would give me a accurate reading of the solution I put inside the wells. I also made sure that I always tapped in every last drop of the solution, to prevent the volume of the solution changing.

I then collected my duckweeds; I used a spatula to scoop them from the pond water onto the white tile, I used a spatula to get the duckweeds out as it prevented any damage to the rootlets, and as it wasn’t sharp no living organisms inside the pond were harmed. Using a mounted needle and magnifying glass I carefully separated the duckweeds with four healthy fronds, of which I used a ruler to measure that the rootlet was in the length between 0.5 – 1.0 cm3. I had placed the duckweeds on a white tile whilst picking the ones I used, so that I was able to pick out the similar coloured fronds more clearly against the white background. By using a magnifying glass I was able to make sure that the duckweeds I picked were all in similar sizes and also were healthy by not having any damaged fronds or rootlets.

I picked out 18 duckweeds with four fronds each, so that one duckweed could be placed into each of the wells in the tray. I then decided to pick another 18 duckweeds, so that instead of putting only four fronded duckweed into a well, I would put 8 fronds, each attached t a rootlet, into each of the wells. I did this because although I checked with a magnifying glass to pick out healthy fronds there may still be a chance that some of the fronds are damaged. This would affect the outcome of my results, if not much photosynthesis could take place in one of the four fronds, so by putting 8 fronds into each well ensured that the maximum amount of photosynthesis, and therefore plant growth could still take place even if there are unhealthy fronds. I used a mounted needle to separate the duckweed easily, without damaging their fronds.

Each time I collected the duckweeds I placed them into a glass beaker which contained tap water, because if I left the duckweeds on the tile without water this could lead to the weeds drying out, and become damaged easily, due to it’s small size and as I was finding quite a large number of particular shaped weeds which took me a quite a long time. Also I did not put any of the duckweeds into the wells until I collected enough, as I wanted the experiment to start at the same time to ensure reliability of the all the replicates, as they will be exposed to the same environment.

After collecting enough duckweed, I carefully placed duckweeds with a total of 8 fronds using a mounted needle and magnifying glass into each of the wells of the tray. I then placed the ice cube tray in another room underneath a light bank, where factors such as temperature and light (intensity and quality) were constant all the way through the investigation, as this would encourage the reliability of the outcome. I also used the ice cube tray to put my duckweeds in as it contained wells that were all the same size and at the same level of height.

I will observe the duckweeds over a 10 day period and check the water in the solutions, as uptake of water and evaporation will take place. In order to fill the wells with water, I will add tap water with a syringe. Each time I will fill the wells to the top with tap water; this ensures that there is the same amount of water in each well, so therefore this increases the reliability of the outcome results. To do this I will use a syringe, as this prevents adding too much water at once, which leads to the overflow of water, and therefore contamination of solutions in their neighbouring wells; the contamination will change the amount of nitrates in each solution.

I will check each day and add water to prevent any wells from drying out or become too concentrated with minerals and nutrients as this can cause problems and affect my results.

I have chosen to add tap water to make up for the loss of water in the wells, this is because tap water contains high levels of minerals in it such as Calcium, Magnesium, sodium and certain trace elements essential for plant growth. Tap water also has a high PH, which affects and encourages the nutrient uptake by plants. Therefore it is important that I use tap water and not distilled water, as it ensures that other minerals do not become a limiting factor on plant growth. Consequently I am not using distilled water as it is clean of minerals.

However many tap water are not good for plants, often they are treated with chlorine or other chemicals, to make them safer to drink and so these are bad for many plants. To control the experiment, I will water the duckweeds using the same tap water.

Analysis

The previous graph shows the individual results I obtained during the experiment. The graph shows two major patterns labelled trend A and trend B, found through out the range of nitrates exposed to the Duckweeds. Trend A on the graph is between 0%-0.4% x 10-3 concentration of nitrates in solution, this trend shows a rapid increase in growth of duckweeds (increase in the number of fronds) as the concentration of nitrates increases. This increase in trend A lasts until the growth of the fronds reaches the optimum which is at 0.4% x 10-3 concentration of nitrates. This pattern suggests that the growth of duckweeds in this investigation is most favoured at 0.4% x 10-3 concentration of nitrates, as this is the concentration where the maximum number of fronds grew.

Trend B is between 0.4%- 2% x 10-3 concentration of nitrates, this trend shows that as the concentration of nitrates increases from 0.4% onwards the growth of the duckweeds decreases. This is due to the unfavourable amount of nitrates exposed to the duckweeds.

Trend A:

At 0% x 10-3 of nitrate concentration, the number of fronds increased from the initial 8 frond to an average of 20.67 fronds, this increase took place without the presence of any nitrates in the solution. This is because there were already some nitrates present inside the cell, in the required form such as proteins, coenzymes and other nitrogen containing components, essential for the plant to survive and grow. Since nitrogen is already available inside the plant cells the duckweeds in this concentration are able to carry on growing until nitrogen becomes a limiting factor. The presence of nitrogen in the components of the cells meant that the metabolism for respiration, photosynthesis and plant growth could still take place. Without nitrates in the solution, it had a higher water potential so osmosis occurred where the water in the solution moved from the solution into the plant cells of the root, where the water potential of the plant cell was lower, as water moved into the cells, the macro and micro nutrients within the solution were also able to diffuse through. Plant growth still occurred as the plant still used energy obtained from the light bank, water from the solution and carbon dioxide to produce oxygen and simple sugars (photosynthesize). The plant cells were then able to use these sugars to make more complex sugars and starches for storages as energy reserves, to make any stored nitrogen into amino acids then to proteins. This required energy for growth comes from reserve carbohydrates and from actively photosynthesizing fronds.

The present nitrogen performed nitrogen metabolism, which is vital for plant growth.

After the addition of 0.4% x 10-3 nitrates to the duckweeds, the graph shows an increase in growth to an optimum. This increase aids rapid growth as there is the right amount of nitrogen present inside and outside the cells of the roots. This optimum growth suggests that 0.4% concentration is the most favoured environment, for the growth of the duckweeds. The no. of fronds increases from the initial 8 fronds to an optimum average of 32 fronds, so this concentration aided the maximum growth through out investigation.

As there is the correct amount of nitrates and solutes outside the root cells, this gives a favourable water potential value outside the cell. The net uptake of water occurs by osmosis. Osmosis is the passive transport of water across a semi permeable membrane. Because a plant cell has a wall, this affects Osmosis which occurs between the cell and its extra cellular fluid. The combined effects of solute concentration and physical pressure are incorporated into a measurement that is called Water Potential. Water potential determines the direction of movement of water, so water moves from a region of higher water potential to regions of lower potential. So the solutions containing 0%- 0.4% x 10-3 nitrate concentration had a higher water potential than the fluid inside the cells cytoplasm. Therefore this caused water from the solution to move inside the root cells of the duckweeds, and prevent dehydration. So these two solutions had the most favourable uptake of water.

Water is a very important component for plant, especially in photosynthesis and in nutrients uptake. The more water taken inside by the cells means that the photolysis part of water during photosynthesis takes place more, and therefore H+ from water is used for reducing the co- enzyme NADP. Reduced NADP is then used to transport the H+ and reduce organic molecules for the synthesis of carbohydrates and sugar. The high water potential outside the root cells of the duckweeds led to more water entering the cells, so more hydrogen ions were produced from the splitting of water by the light energy absorbed from the light banks. The increased amount of H+ ions helped the plant to grow and photosynthesize. This is because the most important active transport protein in the plasma membrane of the plants cell is the proton pump. This uses energy from ATP to pump H+ out of the cells, more H+ pumped out results in a proton gradient, with a higher H+ concentration outside the cell than inside. The gradient is a form of stored energy, because the H+ ions tend to diffuse ‘downhill’ back into the cell. Plant cells use energy stored in the proton gradient to drive the transport of many different solutes. This proton pump contributes the uptake of k+ ions by the root cells as it is a cation so it is driven into the cell by the membrane potential, through transport protein.

Nitrogen in the solution were taken up in the form NO3 – , so the root cells accumulates these anions by coupling their transport to the inwards diffusion of H+ ions through a Cotransporter. Since the investigation was on the effect of the nitrate concentration on growth, all the other nutrients needed for the plant were obtained from the tap water and solution, to prevent the growth to be affected by any other limiting factor.

The macro nutrients required for growth apart from Nitrogen are potassium, phosphorus, Magnesium and Sulphur. Micro nutrients needed are Chlorine, iron and Manganese. These nutrients were provided from both the solution and tap water.

In both of the 0% and 0.4% x 10-3 concentration of nitrates, the high water potential meant that enough water entered the root cells and generated the uptake of both the macro and micro nutrients needed for growth. This is why all the fronds in both the concentrations were dark healthy green coloured, as they were rich in water and all nutrients. The solution in these two concentration of nitrates were hypotonic, so the cell wall in these duckweeds helped maintain the water balance, the plant cells swell as water enters by osmosis, but however the elastic wall expands only to so much before it exerts a back pressure on the cell that opposes further uptake. At this point the cell is turgid (very firm), which is the healthiest state for the plants generally; this is why the fronds in this condition looked very healthy and green.

This is also the reason why maximum amount of growth did not occur in the 0% concentration and it proves that growth is favoured by nitrogen, as the duckweeds in 0% x 10-3 concentration of nitrates although had a higher water potential solution, did not have any nitrogen present so were not able to grow to their maximum. In 0.4% concentration, the presence of nitrates allowed the duckweeds to grow to their maximum.

Trend B:

At 0.8% x 10-3 concentration of nitrates, there is a rapid decrease in the number of fronds, to an average of 15.33, the observations that were made were that the fronds were of pale green/ yellow in colour.

At 1.2 % x 10 -3 the number of fronds continued to decrease more to an average of 4.67, at 1.6% x10-3 there was an average of 2.33, so there was significantly less fronds compared to in trend B. The colour observations made here was that fronds were in pale green/ brown in colour. Finally the highest concentration of nitrates in the experiment 2% x 10-3 had 0 fronds, as the initial Duckweeds died.

There was a decrease in the number of fronds in all the concentrations in trend B. This is due to Osmosis. The solution outside each of these root cells had a lower potential water potential, and so in the 0.8% x 10-3 concentration there was a vast amount of decrease in water uptake, resulting in less nitrates uptake, which therefore decreased the growth of fronds.

However the water potential in the solutions 1.2%- 2% x 10-3 of nitrates concentration was so low that the water potential in the plant cells cytoplasm was higher, and therefore resulted in water moving out of the cells cytoplasm and into the solutions. And so as a result there was no nutrient uptake, the exposed solutions were hypertonic, which meant that the cells lost water to their surroundings and shrunk. This caused the plant to wilt and die, and so no growth takes place. The dead fronds turned brown in colour.

At 2% x 10-3 concentration all the fronds in the duckweeds died, because due to the lower water potential in the solution, the water carried on moving out of the cell, and this carries on until the water potential both inside and outside the cell reaches an equilibrium. How ever the water potential in this solution was to low that it caused all the water to be drained out of the cell and cause it to die, since equilibrium was still not reached.

At 0.8% x 10 concentration of nitrates, a deficiency of potassium and Magnesium could be detected, as the fronds were yellow in colour. Potassium is a cofactor that functions in protein synthesis, it also aids processes such as active transport and major solute functioning in water balance. The yellow colour obtained is because there was a shortage in chlorophylls which means that there is less light energy trapped due to fewer amounts of pigments; this is because of less magnesium – potassium complex being formed. Magnesium is a component of chlorophylls, it activates many enzymes. This yellow colouring of the fronds is known as Chlorosis. The fronds in 0.8%-2% x 10-3 concentration show a significant shortage in Nitrogen, which is a component of nucleic acids, proteins and hormones, so there was hardly any growth.

Principles and concepts

In the solutions where the uptake of nitrogen took place the fronds on the duckweeds grew. This is because nitrogen is an essential component for the plant’s growing process. Nitrogen is used in the manufacture of the nitrogenous co- enzyme NADP, it also in the energy used as ATP, as it contains the nitrogenous base Adenine. These two components need nitrogen to be taken in, in order to be produced. They are also the most important components for survival. NADP is used as a hydrogen accepter and transporters. The ATP molecule is used to transfer energy to metabolic places. So the solutions, which allowed the most uptake of nitrates, produced a greater number of ATP and NADP molecules, and their increased synthesis aided the growth of plant tissue.

In the thylakoid membranes of the plant, the light dependant part of photosynthesis took place. Here the light energy supplied by the constant light banks were absorbed by the chlorophyll and other pigments. The more nutrients that were taken up by the roots such as the magnesium and potassium meant that more pigments such as chlorophyll were manufactured. The lights are then harvested in photosystems so that maximum amount of light is taken inside. The light energy absorbed causes the electrons within the chlorophyll to become excited. The energy released synthesises ATP from ADP and an inorganic phosphate. Also during this stage the water absorbed by the roots in the solution, undergo photolysis. The H ions produced from this reduce the NADP into NADPH.

These molecules produced are the essential components of the Calvin Cycle, this is water is also the reason why water is vital, as it provides the H ions, without these ions the Calvin Cycle cannot take place. This Light- independent reaction is where the main manufacture of sugars and carbohydrates takes place, with the help of the reduced NADP and energy providing ATP molecule. The light – independent reaction takes place in the stroma of the chloroplast, and the reaction needs energy and H ions to keep the cycle going.

B The fronds were in a constant environment, where each frond was exposed to the equal amount of CO2. The 5 carbon compound RuBP binds to the carbon dioxide, with the help of the enzyme Rubisco to produce another compound, GP. The ATP provides the energy for the synthesis of the synthesis of this compound into sugars such as sucrose. The NADP provides H+ ions for the reduction of organic compound to produce sugar. The Calvin cycle makes carbohydrates, lipids and protein via amino acids. The sugars produced ( mostly sucrose) are transported from the leaves to actively growing regions to provide energy for growth and respiration.

The nitrogen is also the component of proteins, which is the polymer of amino acids. Each amino acid contains the carboxyl group, R group and the nitrogen containing amine group. These amino acids link together by peptide bonds, forming a long chain of polypeptides. The chain leads to different structures of proteins. Two kinds of proteins can be made fibrous or globular proteins. The globular proteins that are made are like enzymes such as the Rubisco used in the Calvin cycle. Enzymes in plants are needed to make parts of the plants like chloroplasts and pigments. The membrane of these plant cells contains scattered proteins, which in the root cells allow the uptake of nitrates and other essential nutrients.

Proteins are vital components in a plants variety of metabolic pathways and processes. Proteins make up the molecular structure of DNA, RNA and host of other critical metabolic processes required for plant growth.

The plant grows using, mitosis as cell division, and therefore copies the previous cells DNA in order to divide and replicate. The cells therefore need to make many new DNA’s in each new cell. DNA is made up of 4 nitrogenous bases, adenine, guanine, cytosine and thymine. So the nitrates taken up by the roots are also used to manufacture the DNA, DNA carries the instructions for the cells in the form of codes to make particular proteins. The nitrogenous bases are attached to a 5 carbon sugar and a phosphate group, joined by a condensation reaction to form a nucleotide. Two strands of poly nucleotides join together to make the DNA, which is copied into every other new cells.

Nitrogen also stimulates the growth of roots, which enables efficient uptake of all other nutrients. Amino acids are made in the root tips and carried to growing areas in the plant to make proteins.

From the table that contains all the results pooled from my class, I will use the results to consider the hypothesis made earlier on. The reason I am using the pooled results and not my individual ones is because altogether there are 30 replicates for each concentration in the pooled results where as in my individual one there is only three. The greater the number of replicates means the more reliable and accuracy the results are likely to be. Using Trend A and Trend B I will firstly calculate the standard deviation, and using these results I will be able to carry out two t-tests, one for each of the trends. The outcomes of the t- test will allow me to conclude whether to accept the null hypotheses or the alternative hypotheses.

The Alternative Hypotheses of this experiment is : There will be a significant difference between the growth of the duckweeds fronds and the concentration of nitrates in the solution.

The Null Hypotheses of this experiment is : There will be no significant difference between the growth of the duckweed fronds and the concentration of the nitrates in solution.

To calculate the mean of each concentration I added all 30 replicates and divided by 30.

Mean Values of :

0% = 22.3

0.4% = 22

0.8% = 12.7

1.2% = 4.23

1.6% = 1.93

2% = 0.57

A t-test is carried out to compare the mean values in trend A and trend B. It also ensures that the difference between the two means is a genuine effect, which allows us to decide whether the difference is due to chance or not.

For each trend if I accept the null hypothesis, then I must reject the alternative, and vice versa. The alternative hypotheses can only be accepted if we are 95% or more sure that the null hypothesis is not correct.

The standard deviation formula used is

The standard deviation of

0% = 6.58

0.4% = 7.67

0.8% = 4.91

1.2% = 3.00

1.6% = 2.56

2% = 1.57

Looking at the standard deviation value, the o.4 % value is big so it means that the result values are quite spread out this could be the reason why the mean is smaller than the mean of 0%. As it is this spread out data that resulted in the average value of 0.4% to be smaller than the 0% average unlike in my individual results.

Trend A is between 0%- 0.4% x 10 concentrations of nitrates.

Trend B is between 0.4%- 2 % x 10 concentrations of nitrates.

I have decided not to use the values of 2% concentration in the t- test, as all the fronds had died, and using the 0 values will just increase the spread of data. So it will be more reliable not use them values, therefore the t- test carried out for trend B will be between 0.4% to 1.6%

The t- test formula that I am using is:

The t- test for trend B

The t-test for trend A

So the t value trend A is 0.124, and the t value in trend B is 13.6. The degrees of freedom for these t- tests carried out is 58. This is calculated as 30 x 2 replicates and minus 2 gives a total of 58. The standard error that will be used to compare these T-tests values is 5% since the critical value is 95%. Looking at the t- value table there is no degrees of freedom value for 58, so I will use the one before it which is 40. At 5 % level of significance the critical value is 2.021, so this means that my t value should be equal to or greater than this in order to be at least 95% confident that the difference between the two means is significant. However the value obtained by the t-test in trend A is 0.124 and this is lower than all the critical values in that degree of freedom. Therefore I am less than 80% confident that the difference is significant, this significance is too small, and so does not prove any difference between the two means in trend A is not by chance alone. So for this trend I will now have to reject the alternative hypotheses and accept the null hypotheses.

For trend B the critical value for 5% significance is also 2.021, the value obtained by the t-test is 13.5, and this is significantly greater than the critical value. This means that the probability that chance alone may have caused the difference between the two means in trend B is less than 0.01%. Therefore I am more than 99.9% confident that the difference between the two means for Trend B is significant. Therefore for this trend I can now reject the null hypotheses and accept the alternative hypotheses that there will be a significant difference between the effect of Nitrate concentration and the growth of duckweed fronds.

From my investigation I have found that the 0.4% is the most favoured environment on the growth of the duckweed fronds, as it is receiving the maximum amount of all nutrients, due to it’s favourable water potential solution.

Evaluation

The results obtained I found were reliable, because many replicates were carried out, for each of the nitrate concentration. This gave me a reasonable amount of data to work with and carry out statistical test. The result obtained from the t – test in Trend A did not provide enough significance in order to accept the alternative hypothesis. But the value in Trend B allowed me to accept the alternative hypotheses and reject the null. I think over all the results are reliable, but since the results were pooled from the class there may have been one or two anomalies. As the standard deviation in the 0.4% x 10-3 concentration of nitrates in trend A is more spread out because there were results that were unexpectedly small, such as 8 and 7 fronds, compared to 36 and 33fronds from the initial 8. So although there was the right increased amount of fronds in the concentration there was also a small amount of frond growth, which are anomalous results. This resulted in not a lot of difference between the mean values of 0% and 0.4% concentrations of nitrates.

On the other hand the results in trend B are very reliable, and show what was predicted to happen in the conclusions made earlier on due to osmosis effect.

In order to increase the reliability of the results factors such as the PH were kept constant. As the PH used was not too acidic or too alkaline, so that PH does not become a limiting factor for growth. The solutions used were dilute, so were a suitable environment for the duckweeds to grow. If the duckweeds were placed in a too acidic environment, then the duckweeds will not be able to grow properly as the Chlorosis process will take place, since the frond will not be able to get enough nutrients to make their pigments. To increase the reliability of the results 30 replicates were pooled together to allow me to carry out a statistical test, these 30 replicates all started and ended the investigation.

The major factors for survival of the plant were controlled as best as possible. The light banks were on all the way through the experiment which provided each duckweed with the maximum amount of light energy, so that they can photosynthesize as much as possible. Also since they were all exposed to the same light bank each duckweed in the experiment was exposed to the same quantity and quality of light. This increased the reliability of the results since each duckweed have equal chance of absorbing light and using the energy to grow. The temperature was controlled as there was an electrical heating system in the room which provided each replicate with the equal heat needed in order to carry out metabolic processes. Also this temperature was always kept constant through out the experiment and was controlled as best as possible. This increased the reliability of the results as an increase in temperature of will lead to an increase in the growth as processes such as the Calvin Cycle are enzyme controlled, so therefore more sugars and energy needed for growth will be supplied, and hence a decrease in temperature will slower the rate of growth, and therefore cause the results to be unreliable. The experiments were all held in the same room, so that other limiting factors such as carbon dioxide were controlled.

Each duckweed used was from the same pond, this increased the reliability of the results, because before staring the experiment the duckweeds all had the same nutrients and components inside the cells. As if they were all from different ponds, they may have been polluted and contained different nutrients inside them which could affect their growth rates.

The same tap water used increased the reliability of the results as tap water from different taps contain different amount of nutrients.

However to the low t- test value obtained in trend A means that there may be factors that affect the reliability of the results. So the factors that could affected the growth may be the size of the fronds, as even with the use of the magnifying glass it was not really possible to make sure that all the fronds were the same sizes accurately. Therefore if the fronds size were slightly bigger this would have affected the results because the plant would have carried out an increased photosynthesis so growth increased as there was more light energy available to make sugar and synthesize proteins for growth. And so a smaller frond meant less photosynthesis and energy provided for the plant to grow so this is a limitation to the equality in growth.

Another limitation was that the thickness in rootlets of the duckweeds was not considered, as they were too tiny to be able to measure with a ruler. This will affects the results obtained because a thicker rootlet meant that there was a bigger surface area for the root to absorb more water and uptake more nutrients, this therefore means that more nitrates are taken up and so increased growth. A thinner root would mean that there are fewer uptakes of nitrates and so decrease growth. This may be factor why in trend A the 0.4 % x 10 concentration of nitrates had the greatest spread of data, from its standard deviation.

Also another factor which could have affected the results is that the use of the mounted needle could have damaged the duckweeds, so therefore some duckweeds may not have photosynthesised and took up nitrogen as much as other duckweeds. This would have led to a decrease in frond growth.

Another major limitation was evaporation. Over the weekends evaporation would have occurred, and the plants were not watered then, this meant that the concentration of the solutes present inside the solution increased. This lead to a lower water potential of the solutions than usual, and so the results would have been affected, This is because not as much water entered the plant cells, so in more concentrated solution it would have led to dehydration of the cells. Therefore less growth of fronds takes place.

Another major limitation of the experiment was the growth of algae. Algae were present in some replicates of the 2% x 10 concentration of nitrates, so this would have affected the results. Algae are aquatic plants and so compete for the same factors of duckweeds, so they would have taken up nutrients in the solutions, leaving not as much for the duckweeds. And so the duckweeds were not able to grow as much.

Over all my results were reliable enough to show that the growth was increased by nitrogen if it was in the plant was surrounded by the correct water potential.

Basically this is the process that occurs in eutrophication in rivers and lakes near farms, where fertalizers containing nitrates leak in the water. The plants living in the water undergo the same process, as their growth increase due to the increased amount of nitrogen they receive.

If I were to carry out the experiment again I would use more replicates. And also use a more close range of nitrate concentration as this will give me a more reliable outcome.

Principles and concepts

In the solutions where the uptake of nitrogen took place the fronds on the duckweeds grew. This is because nitrogen is an essential component for the plant’s growing process. Nitrogen is used in the manufacture of the nitrogenous co- enzyme NADP, it also in the energy used as ATP, as it contains the nitrogenous base Adenine. These two components need nitrogen to be taken in, in order to be produced. They are also the most important components for survival. NADP is used as a hydrogen accepter and transporters. The ATP molecule is used to transfer energy to metabolic places. So the solutions, which allowed the most uptake of nitrates, produced a greater number of ATP and NADP molecules, and their increased synthesis aided the growth of plant tissue.

In the thylakoid membranes of the plant, the light dependant part of photosynthesis took place. Here the light energy supplied by the constant light banks were absorbed by the chlorophyll and other pigments. The more nutrients that were taken up by the roots such as the magnesium and potassium meant that more pigments such as chlorophyll were manufactured. The lights are then harvested in photosystems so that maximum amount of light is taken inside. The light energy absorbed causes the electrons within the chlorophyll to become excited. The energy released synthesises ATP from ADP and an inorganic phosphate. Also during this stage the water absorbed by the roots in the solution, undergo photolysis. The H ions produced from this reduce the NADP into NADPH. These molecules produced are the essential components of the Calvin Cycle, this is water is also the reason why water is vital, as it provides the H ions, without these ions the Calvin Cycle cannot take place. This Light- independent reaction is where the main manufacture of sugars and carbohydrates takes place, with the help of the reduced NADP and energy providing ATP molecule. The light – independent reaction takes place in the stroma of the chloroplast, and the reaction needs energy and H ions to keep the cycle going.

B The fronds were in a constant environment, where each frond was exposed to the equal amount of CO2. The 5 carbon compound RuBP binds to the carbon dioxide, with the help of the enzyme Rubisco to produce another compound, GP. The ATP provides the energy for the synthesis of the synthesis of this compound into sugars such as sucrose. The NADP provides H ions for the reduction of organic compound to produce sugar. The calvin cycle makes carbohydrates, lipids and protein via aminoacids. The sugars produced ( mostly sucrose) are transported from the leaves to actively growing regions to provide energy for growth and respiration.

The nitrogen is also the component of proteins, which is the polymer of aminoacids. Each amino acid contains the carboxyl group, R group and the nitrogen containing amine group. These amino acids link together by peptide bonds, forming a long chain of polypeptides. The chain leads to different structures of proteins. Two kinds of proteins can be made fiborous or globular proteins. The globular proteins that are made are like enzymes such as the Rubisco used in the Calvin cycle. Enzymes in plants are needed to make parts of the plants like chloroplasts and pigments. The membrane of these plant cells contains scattered proteins, which in the root cells allow theuptake of nitrates and other essential nutrients.

Proteins are vital components in a plants variety of metabolic pathways and processes. Proteins make up the molecular structure of DNA, RNA and host of other critical metabolic processes required for plant growth.

The plant grows using, mitosis as cell division, and therefore copies the previous cells DNA in order to divide and replicate. The cells therefore need to make many new DNA’s in each new cell. DNA is made up of 4 nitrogenous bases, adenine , guanine, cytosine and thymine. So the nitrates taken up by the roots are also used to manufacture the DNA, DNA carries the instructions for the cells in the form of codes to make particular proteins. The nitrogenous bases are attached to a 5 carbon sugar and a phosphate group, joined by a condensation reaction to form a nucleotide. Two strands of poly nucleotides join together to make the DNA, which is copied into every other new cells.

Nitrogen also stimulates the growth of roots, which enables efficient uptake of all other nutrients. Amino acids are made in the root tips and carried to growing areas in the plant to make proteins.

Evaluation

The results obtained I found were reliable, because many replicates were carried out, for each of the nitrate concentration. This gave me a reasonable amount of data to work with and carry out statistical test. The result obtained from the t – test in Trend A did not provide enough significance in order to accept the alternative hypothesis. But the value in Trend B allowed me to accept the alternative hypotheses and reject the null. I think over all the results are reliable, but since the results were pooled from the class there may have been one or two anomalies. As the standard deviation in the 0.4% of tren A is more spread out because there were results that were unexpectedly small.

Cite this Effect of nitrate concentration on the growth of Duckweeds

Effect of nitrate concentration on the growth of Duckweeds. (2017, Jul 22). Retrieved from https://graduateway.com/effect-nitrate-concentration-growth-duckweeds-172/

Show less
  • Use multiple resourses when assembling your essay
  • Get help form professional writers when not sure you can do it yourself
  • Use Plagiarism Checker to double check your essay
  • Do not copy and paste free to download essays
Get plagiarism free essay

Search for essay samples now

Haven't found the Essay You Want?

Get my paper now

For Only $13.90/page