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October 23, 2012 Ad. Biology, Period G Interspecific and Intraspecific Plant Competition Abstract A study was conducted to address the problem of interspecific and intraspecific competition among wheat and mustard plants. It was hypothesized that increasing the plant density, and therefore increasing intraspecific competition, would negatively impact the plant biomass. It was also hypothesized that interspecific competition would have a stronger negative effect on the plant biomasses. This was tested by planting varying numbers wheat and/or mustard plants in pots, and measuring their biomass.

The data confirmed the above hypotheses. Findings suggest that intraspecific competition and increasing plant densities had a negative effect on plant biomass, however, interspecific competition had a more severe negative effect. The future study of this topic could allow for greater agricultural success by developing new means of spacing plants, and fertilizing them to combat intraspecific competition. This could also allow for a greater understanding of how to combat interspecific competition in agriculture. Hypothesis

Before testing began, the researcher hypothesized that if intraspecific competition was increased, than it would have a negative impact on the overall biomass of the plants, however, if the amount of plants involved in intraspecific competition per pot increased, than the biomass would be more greatly negatively impacted. If interspecific competition increased, than it would have a stronger negative effect on the plants involved in it, even in lower densities. However, the researcher postulated that if plant density increased, than it would also have a negative effect on the overall biomass of both plant species.

Materials and Methods • 42 equal, 4 inch pots • Artificial soil mixture • Mustard seeds • Wheat seeds • Tray (to hold pots) • Supplemental light source • Water • Scissors (for weeding) • Data sheet • Razor blade • Electric balance • Labels • Graduated cylinder 1. The plants were labeled by section, pot number, and number of mustard and/or wheat plants 2. Each 4 inch pot was filled with soil, which was then packed down to ? inch below the rim. 3. The required number of seeds for each treatment was counted out. A few extra were added to ensure that enough seeds would germinate. . The seeds were evenly distributed over the soil surface, and covered with ? of an inch of potting soil. 5. The pots were then checked for uniformity of soil amounts. 6. The pots were put in the supplied tray, and placed under a supplemental light source. They were then routinely watered (50-75mL) 7. After one week, the number of plants was counted. Any extra plants were carefully cut with scissors as close to the soil as possible. The plants were then periodically checked for extra growth, and any that occurred was removed. 8.

The weekly condition of the plants was checked and observations were recorded. 9. Prior to harvesting, the total number of plants in each pot was recorded. 10. A razor blade was used to cut the plant shoots off at soil level. A balance was used to determine the biomass of the required species. 11. The per plant biomass was then calculated for each pot 12. The average per plant biomass was calculated for the pots with only one plant species 13. The standardized per plant biomass was then calculated for each pot by dividing per plant biomass by the average biomass.

There were multiple variables in this experiment. The controlled variables included the size of the pots used, the quality and amount of soil placed in each pot, the amount of light each plant received, the amount of water each plant received. There was no control group in this experiment. The dependant variable was the amount of plant growth, and the independent variable was the amount and type of plants in each pot. Results: (Data, Observations) [pic] This table displays the biomass, baseline, and standardized biomass for mustard in an intraspecific competition setting. [pic]

This table displays the biomass, baseline, and standardized biomass for mustard in an interspecific competition setting. [pic] This table displays the biomass, baseline, and standardized biomass for wheat in an intraspecific competition setting. [pic] This table displays the biomass, baseline, and standardized biomass for wheat in a interspecific competition setting. [pic] This graph displays the effects of intraspecific competition on mustard and wheat plants. The graph has a negative slope, displaying the negative effect of intraspecific competition on both the mustard and wheat plants. pic] This graph displays the effects on interspecific competition on mustard and wheat plants. The negative slope displays the severely negative effect on both mustard and wheat plants. [pic] This graph displays the relationship between interspecific and intraspecific competition in the wheat plants. The negative slope shows the negative effect of both interspecific and intraspecific competition on wheat plants. [pic] This graph displays the relationship between interspecific and intraspecific competition in the mustard plants.

The negative slope displays the negative effect of both interspecific and intraspecific competition on mustard. Conclusions The results supported the hypotheses. Interspecific competition was shown to have a more serious negative affect on both mustard and wheat plants. Although intraspecific competition did negatively impact both plant species, the struggle for life sustaining resources against plants of another species had a more significant effect. This trend is evident in the data. Intraspecific competition is apparent for both species, and has a more significant negative impact as the number of plants for each pot increased.

For example, the per plant biomass of mustard in an intraspecific competition setting with only two plants ranged from 1. 146 to 2. 548 grams. When the number of mustard plants per pot was increased to four, the per plant biomass ranged from 0. 842 to 1. 824 grams, this shows a decrease. When the number of plants per pot was increased to eight, the per plant biomass’s ranged from 0. 424 to 0. 637, this shows a decline from both of the previous data ranges. Lastly, the number of plants per pot was increased to sixteen, this data ranged from 0. 319 to 0. 329 grams.

As the number of mustard plants per pot increased, the per plant biomass decreased. This shows the negative effect of intraspecific competition on Mustard, confirming the hypothesis. As the struggle for resources increased with plant density, the plants became less vibrant. Intraspecific competition was also evident in the wheat plants, again confirming the above hypothesis; for the pots with the least amount of wheat plants, two, the per plant biomass ranged from 0. 794 to 1. 036 grams. When the number of plants per pot was increased to four, the range of per plant biomasses’ decreased to 0. through 0. 75 grams. The biomass ranges for eight plants per pot was 0. 382 to 0. 484 grams, and the ranges for the pots with sixteen plants was 0. 333 to 0. 351 grams. As the number of plants per pot increased, the per plant biomass decreased, again emphasizing the detrimental effect of intraspecific competition on plants. The baseline and standardized measurements also reflected this negative trend. Interspecific competition also had an even more significant negative effect on both the mustard and wheat plants, again confirming the above hypothesis.

The effect of interspecific competition on mustard was quite apparent when looking at the data. The mustard plants with the least amount of intraspecific and interspecific competitors were the most successful. For example, in the pots with two mustard and two wheat plants, the per plant biomass’s ranged from 0. 18 to 1. 158 grams. These plants were the most successful, due to the lesser amount of interspecific competition from wheat. As the amount of interspecific competition increased, the plant biomasses decreased. The mustard plants with competition from four wheat plants had per plant biomasses ranging from 0. 81 to 0. 328 grams. This range has significantly decreased due to the increased amount of interspecific competition from wheat. As the amount of wheat plants increased to six, the per plant biomasses ranged even more, from 0. 237 to 0. 491 grams. Although this is a greater per plant biomass, the hypothesis is still confirmed because plant density must be considered. Some of the plants with only two or four wheat plants providing interspecific competition faced massive intraspecific competition, with ten, eleven, or sixteen mustard plants, lowering the per plant biomasses.

This data confirms the hypothesis, that interspecific competition would have a more severe detrimental effect on the per plant biomasses. The mustard plants faced with only intraspecific competition were considerably more successful than those faced with the added challenge of interspecific competition. Interspecific competition also had a severely negative effect on wheat plants faced with mustard competitors. The number of mustard competitors began at two, with per plant biomasses ranging from 0. 577 to 0. 938 grams. When the number of mustard plants increased to six, the per plant biomasses ranged from 0. 487 to 0. 12 grams. Lastly, the number of mustard plants increased to fourteen, creating a per plant biomass range of 0. 452 to 0. 619 grams. These ranges show a significant decrease as the amount of interspecific competition increased. This again confirms the hypothesis, showing that interspecific competition not only has a negative effect on the per plant biomass, but has a more serious negative effect than intraspecific competition only. This is due to the fact that the plants involved in interspecific competition not only face competition from the competitor species; they also struggle with intraspecific competition.

The standardized and baseline data also supports the per plant biomass and the hypothesis. This was a relatively valid experiment, very few errors occurred during the testing, and they were minor. A few factors that must be considered when considering the validity of the experiment was that the plants were relatively close together on the tray, a few of the plants might have been crushed, which could have damaged them. Another error might have occurred when the plants were being counted; some of the pots had many plants in them that got tangled together.

Attempting to separate them in order to count them might have damaged them. Due to the validity of the data, there is no data that should not be considered. This data and research could be extremely beneficial if it were to be expanded on. Understanding the effect of interspecific and intraspecific competition on various types of plants could be very useful for farmers and those that work in agriculture. If this research was to be expanded upon, a greater knowledge of the different ways plants struggle to gain resources and how certain plants can be more successful in doing this could be gained.

This would allow agricultural worker to determine a better way to combat intraspecific competition, possibly through plant spacing and new fertilizers. Farmers could also potentially decrease interspecific competition, through developing new ways of combating competitor plants or modifying the species they want to thrive. If this experiment was to be continued in order to refine the hypothesis, even more trials would be completed, with a greater number of plant species. These species would include a wider amount of diversity. The experiment could be put in place for any variety of agricultural plants.

The results of this testing could allow for greater agricultural success. This would allow the effect of competition amongst a larger range of a variety of plants to be studied, and would increase the understanding of the concepts involved in interspecific and intraspecific competition. Questions 1) Intraspecific competition was not more intense than interspecific competition. The plants faced with interspecific competition had considerably more trouble. This is because they were faced with both interspecific competition from either the mustard or wheat plants.

They were also faced with intraspecific competition from the plants of their own species. This significantly lessened their ability to gain resources and flourish in their environment. 2) If the experiment had continued, the plants faced with high density, high amounts of interspecific competition, or that were facing large amounts of intraspecific competition would have continued to struggle. Eventually, the weaker plants involved in intraspecific competition would have been overwhelmed, and the strongest plants from both species would flourish.

One of the species involved in interspecific competition would have taken over the other, most likely mustard. Wheat could have developed grain in an intraspecific setting of four evenly spaced wheat plants per pot if the experiment had continued. Mustard could take over wheat in a high density condition with a very low density of competitors. 3) I do not think considering the biomass of the potential competitors would have a strong effect on the graphs. This is because regardless of how the biomass is determined, the competitor will still have the same effect on the plant it’s competing with.

This is a different way of gathering data, the outcomes of the interspecific and intraspecific competition will remain the same regardless of how the data is gathered.

References “Competition Among Plants. ” Pnas. University of Nevada, n. d. Web. 12 Oct. 2012. “INTERSPECIFIC COMPETITION. ” The Institute for Environmental Modeling (TIEM). N. p. , n. d Web. 12 Oct. 2012. http://www. tiem. utk. edu/~gross/bioed/bealsmodules/competition. html “Intraspecific Competition. ” classes. classes, n. d. Web. 12 Oct. 2012.

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