The effect of nutrient concentration on duckweed

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Lemna slight, or duckweed, is a tiny plant that floats on the surface of stagnant water that is generally rich in nutrition. Phosphorus is a crucial macronutrient inside the growth of marine plants. We all tested the result of phosphorus on duckweed population progress using a control medium abundant with nutrients and compared it to the population growth within a medium that lacked phosphorus. Each treatment had five replicates that began in beakers with 40 duckweed thalli, cultivated in a clinical setting for 14 days beneath 140-W signals at space temperature.

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A regression demonstrated that there were significant development in all the populations (P<0.05), and a t-test resulted in a significant difference between the growth rates of each condition on day 3 (t=1.37, P>zero. 05) and day 14 (t=5. eighty six, P<0. 05). The intrinsic expansion rate, l, for the nutrient abundant treatment was 0. 14 and 0. 08 to get the chemical lacking treatment, therefore the medium containing phosphorus had a more quickly growth rate than that without phosphorus. Phosphorus is known as a limiting take into account the growth of duckweed, and therefore affects the people growth rate.


Lemna minor, additionally known as duckweed, is a member of the Lemnaceae relatives (Monette ainsi que al. 2006). It is a small aquatic grow found floating on the surface of flat, nutrient abundant waters. Every plant, known as the thallus, is usually comprised of a tiny leaf placed on a single rootlet, which is located below the surface of the water. In order for duckweed to multiply, new thalli develop surrounding the edges in the initial leaf, resulting in clumps. The plant inhabitants increases geometrically to speedily cover the top of continue to water within a brief time frame. However , this is apparent if environmental circumstances such as light, nutrients and temperature are generally not limited (Taylor, 2011).

The nutrient concentration of the water in which duckweed resides greatly affects the growth price. The fast reproduction price of Lemna minor demonstrates the idea that duckweed can absorb large amounts of nutrients just like nitrogen and phosphorus (Monette et al. 2006). Due to their free-floating framework, aquatic plants must obtain their nutrition from the drinking water column as well as the atmosphere, as they cannot accomplish nutrients from your sediment listed below. With the exception of carbon dioxide, aquatic plant life have a lower possibility of obtaining nutrients as most of their tea leaf surface can be exposed to the atmosphere, rather than the water. Therefore , when nutrition are limiting the growth price of duckweed suffers hugely (Scheffer ainsi que al. 2003).

Free-floating plant life are outstanding competitors in the competition for light although submerged, grounded aquatic vegetation compete with free-floating plants intended for other nutrients. Rooted plant life can get their nutrients by sediment plus the water column, reducing the nutrients available to the free-floating plants (Dickinson et ing. 1998). Competition for phosphorus increases with population expansion, and the accessibility to phosphorus in the water steering column is reduced because of the uptake by submerged macrophytes (Scheffer et approach. 2003).

Duckweed requires a medium to dangerous of phosphorus available, as it is an essential nutritious for marine plants. It is involved in the mechanisms of the natural photosynthesis, allowing for the availability of organic and natural matter in aquatic conditions (Fogg, 2003). Therefore , all of us hypothesized that the growth of duckweed populations within a medium deficient phosphorus will be lower than that in a channel containing phosphorus. The null hypothesis is that the concentration of phosphorus within the nutrient method does not impact the growth of duckweed, and you will have no significant difference in the inhabitants growth price of the two control organizations.

Materials and Methods

In each of 5 100-ml beakers, 90-ml of progress medium were placed (Table 1). The 5 beakers received a medium exactly like the control group, but were lacking potassium phosphate. Stand 1 . Formula of Lemna Minor culture medium. These ingredients were added to dechlorinated, filtered Antigonish tap water (Taylor, 2011).



Chemical Name Formula Concentration (mg/L) Potassium Nitrate KNO3 350 Calcium Nitrate Ca(NO3)2 ™ 4H2O 295 Potassium Phosphate KH2PO4 100 Magnesium Sulfate MgSO4 ™ 7H2O 100 Calcium Carbonate CaCO3 30 Ferric Chloride FeCl3 ™ 6H2O 0.76 Zinc Sulfate ZnSO4 ™ 7H2O 0.18 Manganous Chloride MnCl2 ™ 4H2O 0.18 Boric Acid H3BO3 0.12 “”””””””””””””””-

Ammonium Molybdate (NH4)6Mo7O24 ™ H2O 0.04

A copper penny was placed in each beaker in order to control cyanobacteria, which may compete with the duckweed (Taylor, 2011). Each of the 10 beakers received 40 duckweed thalli. The beakers were then placed into a mesh basket underneath a 430-W high-pressure sodium lamp, which mimics the wavelengths produced by natural sunlight. The temperature of the lamp was 24C and the room temperature was maintained around 21C. The beakers were observed every day for 14 days. On each day, we would count the number of thalli in each beaker, top up the beaker with distilled water, and gently stir the medium. The baskets were then placed back under the light, but in a different location than before due to the decline in light intensity with distance. The results were recorded in a table each day to keep track of the population growth progress. The mean number of thalli and standard deviation were calculated each day.

Our data was then graphed so we were able to analyze it using statistical methods. A regression was calculated to examine if the slope was significantly different from zero, thus showing that the duckweed grew and there was a linear relationship between the two variables.Two growth curves were produced in order to observe the differences in growth rates between the two groups of thalli, plotting days as the independent variable and number of thalli as the dependent variable.

These means were then ln-transformed to estimate the slopes, which provided the intrinsic growth rates of each treatment to be 0.11 and 0.08 for the control and treatment, respectively. A t-test was used to compare the instantaneous population sizes on three different days of the experiment. On day 3, there was no significant difference between the growth of the control group and the treatment (t=1.37, P>0. 05). However , on day being unfaithful (t=4. twenty four, P<0. 05) and day 14 (t=5. 86, P<0. 05) there is a significant big difference in expansion rates, which will therefore need to eventually develop a difference in population sizes.


The beakers that contains the phosphorus culture moderate and those deficient phosphorus both showed a population increase over the course of fourteen days (Figure 1). For the medium made up of phosphorus, the mean quantity of thalli grew from forty five 0 to 163. 6 20. 7 (SD) as well as the medium lacking phosphorus grew from forty five 0 to 102. 6 10. 6th.

Figure 1 . Growth of Lemna minor, thalli over 14 days under 430-W lights at room temp. The Control population was grown in a complete progress medium, as well as the Treatment is at a method lacking phosphorus. Error pubs are normal deviations. N=5 on each working day.

Both curves resemble a great exponential progress curve, tapering off at the conclusion, but the curve containing phosphorus is a more clearly defined as exponential. This indicates that the progress in the phosphorus nutrient channel was more rapid than the duckweed growth in the phosphorus-lacking method. In order to achieve a line of best suit, we took the natural logarithm of the means of data. The resulting chart shows the overall trend with the population regarding the two masse (Figure 2). The slope of these lines is known as the intrinsic development rate, 3rd there’s r, of the foule. For the people phosphorus rich population we all obtained a growth rate of 0. 11 and for the phosphorus missing population the worth was zero. 08, which means nutrient rich population grew at a faster rate than the nutrient lackingpopulation.

Figure 2 . Ln-transformed suggest number (N=5) of duckweed thalli in phosphorus wealthy and phosphorus lacking nutritional medium. The intrinsic development rate, l, is zero. 11 intended for the chemical rich human population and 0. 08 pertaining to the nutritional lacking inhabitants. The imply growth prices were substantially different (t=2. 16, S<0. 05) between the two populations.

The slopes in the trend lines differed coming from zero, therefore showing that there was progress among both of the foule. A regression was worked out which demonstrates there is significant growth in each populace (P<0.05). In a t-test comparing relative growth rates of the two populations, the calculated t-value was 2.16 and the critical value of t was 1.70 at 28 degrees of freedom. There is a significant difference between our mean growth rates (2.16>1 . 70, P<0. 05). Consequently , we fail to reject the hypothesis there is a significant difference between the growth rates of Lemna small grown in a phosphorus abundant medium and that grown within a medium missing phosphorus.


The duckweed grown in the nutrient rich medium a new higher progress rate than the nutrient missing population, which will supports my own hypothesis. Previous research agrees with these studies, as the productivity of aquatic plants is most likely to be limited by the abundance of phosphate and inorganic nitrogen (Lacoul ainsi que al. 2006).

Previous experiments confirm these kinds of results in finishing that duckweed is generally indicative of high depth zones which can be rich in nutrition (Onaindia ou al, 1995). Limiting the abundance of the nutrients will lead to a decrease in plant growth, but bringing out concentrations of certain substances may limit growth as well. The attentiveness of ammonium ions provides a negative impact among marine plant growth, and is made mostly from pollution. Consequently , the presence of marine plants can easily act as signals of the level of contamination in a given area (Onaindia ain. Al, 1995). These results can contribute to a future test that may evaluation the effect of duckweed focus on nutrients and compounds in the watercolumn that they reside.

General, both of the duckweed populations experienced development over the course of fourteen days. This research could lead to even more research from the population growth of Lemna minor. We could test the effect of growth in conditions with different concentrations of phosphorus, thus allowing us to observe the great growth focus and if too much nutrients may possibly in fact hinder the growth level. To broaden our research, we could test out the effect of phosphorus concentration on terrestrial vegetation to determine unique a constraining factor among all of their growth habits as well.

Nutritional concentration has a large impact on the population regarding duckweed. The moment phosphorus is limiting, the expansion of Lemna minor is definitely reduced drastically compared to that grown below ideal conditions. Our effects agree with this idea as the population expanded in a chemical rich medium had a higher growth rate than the populace grown within a nutrient-lacking method. Lemna minimal has the ability to multiply geometrically, when placed in a limiting environment, the growth is usually deferred.

Literary works Cited

Dickinson, Matthew M., and Jones E. Burns (1998). Competition among Small , and Free-floating, Aquatic Plants. American Midland Naturalist 140. 1: 55-67. JSTOR. Web. twelve Nov. 2011. .

Driever, Steven M., Egbert H. Nes, and Rudi M. Meters Roijackers. (2005). Growth restriction of Lemna minor as a result of high grow density. Marine Botany 81: 245-51.

Fogg, G. E. (2003). Phosphorus in main aquatic vegetation. Water Research 7. 1-2: 77-91. 1 Apr. the year 2003. Web. 9 Nov. 2011. .

Lacoul, Paresh, and Bill Freedman. (2006). Enviromental impact on on marine plants in freshwater environments. Envionmental Reviews 14: 89-136.

Monette, Frederic, Samir Lasfar, Lousie Millettem and Abdelkrim Azzouz.

(2006). Thorough Modeling of Mat Denseness Effect on Duckweed (Lemna Minor) Growth Beneath Controlled Eutrophication. Water Exploration 40. 12-15: 2901-910.

Onaindia, M., N. G Bikuna, and I. Benito. (1995). Marine Plants regarding Environmental Elements in Northern Spain. Diary of Environmental Management 47: 123-37.

Scheffer, Martin, Sandor Szabo, Alessandra Gragani, Egbert H. Van Nes, Sergio Rinaldi, Nils Kautsky, Jon Norberg, Rudi M. Meters Roijackers, and Rob L. M Franken. (2003). Floating Plant Dominance as a Steady State. 100. 7: 4040-045. .

Taylor, Craig R. (2011) Introductory Ecology: Bio 203 Laboratory Manual 2011. Antigonish: St . Francis Xavier University or college.

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