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Abstract
Nitrogen is the mineral needed in most amounts by plants. Factors such as erosion leaching and biotic denitrification serve as a control mechanism to the amount of nitrogen absorbed by the plants. Plants in their inorganic forms take in nitrogen. Some plants also have the ability to assimilate nitrogen in form of urea. Optimal quantities of nitrogen are required for the growth.
Introduction
Invasive plant species can be described as introduced species (Cellot, Mouillot and Henry, 1998). This category of plants easily adapts to new environments in an aggressive manner with high reproduction rates. They lack natural enemies, which combined with their quick multiplication results into an outbreak population in most of their habitants (Luneva, 2009).
Research evidence strongly shows a relationship between the persistence of invasive plant species and the loss of native species with disturbance and fluctuations in soil fertility (DiTomaso and Healy, 2007). The addition of Nitrogen (N) to the soil in disturbed grazing land has been shown to increase the abundance of invasive species, while reduction in N availability has been shown to relatively increase the abundance of the native perennial species. A study showed that the seedling establishment of the medusahead increased with fertilization by NO3- (Thomas, Charles and Douglas, 2003).
The absorption of Nitrate is thought to vary with the type of soil in use due to the difference in water holding capacity. Evidence indicates that the water logging properties of the clay soil promote denitrification and nitrogen loss (Ling, 2010). However, other types of soils such as the sandy loam have a higher percentage of nutrient losses through leaching.
Myosotis scorpioides is a herbaceous perennial plant that belongs to the genus Myosotis, its commonly known as the European forget me not (Ling, 2010). The plant thrives in wet places, and is most commonly found near streams and rivers (Luneva, 2009). Myosotis scorpioides reproduces sexually through seeds and vegetative means by means of stolons that root at the nodes (Rose, 2007). No data is available to indicate the number of seeds that each Myosotis scorpioides plant produces. However, its close relative Myosotis alpestris has been documented to produce between 20 and 120 seeds per plant (DiTomaso, 2007). A study carried identified seedlings of Myosotis scorpioides scattered suggesting that grazing disturbances increases germination (Luneva, 2009). The plant is native in the temperate areas of Europe and Asia but grows exotically in the United States, Canada and other parts of the world. Studies show that the plant tends to escape from gardens to wet areas where it forms dense monocultures (Ling, 2010).
The goal of this study is to evaluate the influence of Nitrate concentrations on the growth and germination of Myosotis scorpioides seeds planted in either sandy loam, silt loam or clay loam (Morris, 2009).
The study hypothesizes that the increase in nitrate availability will increase the percentage of germination and the rate of growth of Myosotis scorpioides. Additionally, the study hypothesizes that change in the type of soil does not affect germination but may cause variation in the rates of growth (DiTomaso, 2007).
The study seeks to investigate the following specific objectives:
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The effect of increasing nitrite concentration and growth of Mysotosis scorpioides.
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The effect of soil variation in the uptake of nitrogen and growth of Mysotosis scopioides
Methods
To determine whether increasing the concentration of nitrates had an effect on the growth and germination of Myosotis scorpioides, seeds of Myosotis scorpioides L. were planted in sandy loam and gardening soil and treated with low, medium, and high concentrations of nitrate. Six 15-cell propagation trays were used in the experiment. The methodology described by Parera and Ruiz was also utilized. The approximate volume of one cell was 270 cm³ thus the amount of substrate required was determined by:
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270 cm³ x 45(cells) ÷ 2 = 6075 cm³ of each substrate.
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Nitrate Concentrations (mg/L) 0mg/L 5mg/L 10mg/L
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Type of substrate Sandy loam n=15 n=15 n=15
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Gardening soil n=15 n=15 n=15
The preparation and distribution of nitrate was as described by Colman; solid potassium nitrate was mixed with deionized water and 20 mL (0.02 L) of the solutions added to each cell. 0 mg/L, 40 mL of deionized water was then added to the cell to be used for trial. Weighing was carried out using an electronic gram scale. The amount of deionized water needed per substrate batch was determined as follows:
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2 (substrates) x 15 (cells) x 0.02 L of solution per cell, for a total of 0.6 L or 600 mL.
To ensure accuracy, 1000 mL beaker, and 50 mL graduated cylinder were used.
The substrates used in this experiment were chosen based on their characteristics, which make them much similar to the soil that is naturally found in riparian areas where Myosotis scorpioides L. grows (Márquez, 2005).
After planting, the propagation trays was transferred to the greenhouse at West Virginia University, where they were observed in accordance to universal greenhouse practices. Each cell was watered with 40 mL of deionized water three times a weekMondays, Wednesdays and Fridays. The weekly amount of deionized water needed is determined by:
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20 mL x 4 (weeks) x 6 (trays) x 15 (cells per tray) x 3 (times a week) = 21600mL.
If this is added to the amount of deionized water needed to make the nitrate concentration:
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21600 mL + 3000 mL = 24600 mL (24.6 L)
Watering was carried out at 10:00 AM and 4:00 PM, during that time the trays are examined for growth presence and progress.
This analysis showed the effect of substrate and nitrate concentration on the growth and germination of Myosotis scorpioides L. Results was considered significant if p < 0.05 representing a confidence interval of 95%.
Results
Increased nitrate concentration resulted to increased growth followed by no germination at all for all the three substrates i.e. nitrate concentration caused a significant (p < 0.05) reduction on the germination in the long-run.
Discussions
The nitrate uptake is versatile and robust in plants because plants have to transport sufficient nitrate to compensate for its total demand. External nitrate concentrations usually vary by five orders of magnitude. In order to function optimally in environmental variation, the energy driving nitrate uptake is found from the proton gradient and kept constant in the plasma membrane by the H+-ATPase.
Nitrate Concentration, Plant Growth and Germination
References
Cellot, B., F. Mouillot, and C. Henry. (1998). Flood Drift And Propagule Bank Of Aquatic Macrophytes In The Riverine Wetland. Journal Of Vegetation Science. 9(5).631-640
DiTomaso, J., and E. Healy. ( 2007). Weeds of California and other Western States.
University of California Agriculture and Natural Resources Communication Services. Oakland, CA. 834 p.
Ling, C. (2010). Myosotis scorpioides. USGS Nomindigeneous Aquatic Species Database, Gainesville, FL. Web.
Luneva, N. (2009). Weeds, Myosotis arvensis L. Common (field) Forget-me not. AgroAtlas. Interactive agricultural ecological atlas of Russia and neighboring countries: Economic plants and their diseases, pests, and weeds. Web.
Márquez A. J. (2005). Lotus Japonicus Handbook. New York, NY: Springer.
Morris P. (2009). Methods Of Environmental Impact Assessment. London: Taylor & Francis.
Rose N. L. (2007). Lochnagar: The Natural History of a Mountain Lake. New York, NY: Springer.
Thomas A., T. Charles, and A Douglas. (2003). Nitrogen effects on seed germination and seedling growth. J Range Manage. 56: 646-654 p.
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