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Allelopathy. Open Investigation Will increasing the number of allelopathic sunflower plants effect the height growth of a non-allelopathic bean plant when the two types of plants are grown next to one another?

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High Level Biology Plant Physiology Open Investigation Will increasing the number of allelopathic sunflower plants effect the height growth of a non-allelopathic bean plant when the two types of plants are grown next to one another? I. DESIGN Aspect 1 Background Information In biology, it is learnt that species competition ensures biodiversity of the ecosystems. Due to biology evolution all plants and animals have developed characteristics and techniques that will enable them to out-compete other species for nutrients, water, territory and other essential resources. Allelopathic plants compete with other plant species through "chemical warfare". A "chemical warfare" refers to the excretion of a collection of chemicals (allelopathy chemicals or allelochemicals) by the allelopathic plant to inhibit the growth on its competitors. Specifically, the height growth of plants is affected by the allelochemicals. The word allelopathy derives from two separate words - allelon which means "of each other", and pathos which means "to suffer". [1] Allelopathy plants releases different classes of chemicals such as phenolic compounds, flavonoids, terpenoids, alkaloids and amino acids. Due to the mixtures of different compounds the effect of allelopathy is greater than individual compounds alone. Plant tissues may contain up to several grams per kilogram of these compounds. [10] Diagram 1.0: Tissue types of the plant stem [8] External stimuli such as ultraviolent radiation from the sun and chemical stressors or fertilisers induce the synthesis of phenolic compounds in plants. [10] Ultraviolent radiation is produced by the sun and also known as the sunlight or sunrays. Sunlight is the primary energy for all living things. When light energy (photons) gets trapped in the chloroplasts of plants it converts into chemical energy. The chloroplast is a structure with in the plant that carries on photosynthesis. The process of photosynthesis produces oxygen and organic compounds such as sugars which allows the plant to grow. [8] Allelopathic substances work like herbicides. Common traced effects of allelopathy include - * Reduced seed germination * Restricted seedling growth, plant height growth and growth of leaves ...read more.


This table shows the average height of the bean plant on day 12, 18, 34, 40 and 45. The overall average height of the bean plants at the end of the experiment is also included in this table. The uncertainty value of the measurement of data is also shown. Day # Average height of plants (� 1 mm) Control 1S 2S 3S 4S 12 33.8 33.0 27.4 25.4 26.2 18 36.8 35.0 30.8 26.4 27.8 34 77.0 70.2 52.0 45.2 38.4 40 78.8 72.2 54.6 47.2 40.8 45 80.2 73.2 57.2 52.0 43.0 Overall average height 61.3 56.7 44.4 39.2 35.2 Note - The uncertainity of measurements is �1mm but value figures are given to one decimal places due to the calculations of averages in between Worked calculations: Calculating the average height of the five repeated tests of the Control bean plant on day number 12 [6] Data points: 33 34 37 33 32 * refer to Table 2.0 � M = 33 + 34 + 37 + 33 + 32 5 = 33.8 Table 2.3: This table shows the standard deviation of the five repeated set of plants for each independent variable - the five repeated tests for Control, bean plant with 1 sunflower, bean plant with 2 sunflowers, bean plant with 3 sunflowers and bean plant with 4 sunflowers. The standard deviation of the five repeated tests was calculated for day number 12, 18 34, 40 and 45 for these were the days of raw data collection for this experiment. Day # Standard Deviation Control 1S 2S 3S 4S 12 1.92 3.08 2.41 2.41 2.77 18 1.92 2.92 1.95 1.95 2.59 34 6.04 5.81 6.96 2.68 4.22 40 4.92 5.36 6.23 1.79 3.27 45 3.83 4.66 6.06 3.81 2.55 Worked calculations: Calculating the standard deviation of the five repeated tests of the Control bean plant on day number 12 [6] Data points: 33 34 37 33 32 * refer to Table 2.0 Mean of data points: 33.8 * refer to Table 2.2 ...read more.


This will decrease the towering factor of sunflower plants on the bean plant. Difficulties occurred when measuring plants with a straight ruler. Difficulty of measuring plant height when plant stem started to bend Because the ruler was straight, it was difficult to measure the plants when the stem started to bend. It was also difficult to line the ruler up with the stem and at the same time note and record the height in millimetres. Imprecision may have occurred when attempting to measure the bent stem due to the ruler being straight. Values and figures may be inaccurate and that would have affected all calculations made in this report. A string should be used to measure the plant. An additional experiment should cut the string at the appropriate place - tip of stem and surface level of soil. Using a string to measure the height will allow flexibility when measuring the bent part of the stem. Use a ruler to measure the string and this will be the height measurement of the plant. Insufficient trials were carried out. Trials were only carried out in one environmental condition Although 5 repeats of tests were carried out for the 5 variables of this experiment, the whole experiment was carried out in one environmental condition. Some plants may grow and prefer certain conditions therefore the conclusion of results can only be made in scope of the environmental condition. This experiment was carried out in winter - and it is known that plants do not grow much in winter and prefer warmer weather. The season would have affected the growth of the plant for plants cannot develop to its maximum growth. This may affected the figures and values and therefore calculations made in this report may be imprecise. The whole experiment should also be carried out at standard lab conditions. In addition, this experiment should be carried out in the plants' preferred season which is Spring. If the results obtained for the other experiments are the same as the original experiment then the results can be stated as being accurate. ?? ?? ?? ?? ...read more.

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