Phenotypic Plasticity Was The Outcome Biology Essay


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The reason of this experiment was conducted to show how light intensities affected the petiole length of the plants called Pothos aureu. The plants tended to have a longer petiole length and faster growth under low-light than the ones under high-light, because the plants were commonly known as the understory plants in the rain forest where had a little light passing through. However, the plants performed their phenotypic plasticity to best adapt to the various environment conditions and increase their survival rates. Therefore, the high-light treated plants should have a slightly slower growth, and a shorter length of petioles than the high-light ones. The experiment was to measure the petiole length of plants in the growth chambers under high and low light intensities. The results demonstrated that the plants under low-light yet had a longer petiole length and significantly faster growth and the high-light treated plants also had an increasing petiole length, but not as long as the other ones. Both of the plants showed their phenotypic plasticity in order to adapt to different environment.


Phenotypic plasticity was the outcome of the various phenotypes produced by a single genotype depending on different environment conditions. It was to allow the organisms to best adapt to the changing environment even in unfavourable conditions for survival which was the genetic adaption ("Crispo E-2008"). According to natural selection of the fittest survival, the species showed less difference of each other under the stable environment than the unstable one. However, the higher the genetic and phenotypic variations around the interacting organisms were, the better the adaption to the environment because the species were interacting to each other, therefore they could have corresponding benefits to the others ("Anurag A. Agrawal-2001"). How was the study performed on species to show their phenotypic plasticity under different environments?

In this experiment, plants called Pothos aureu were being studied, and the petiole length of the plants were examined in the response of novel habitats, which had a high and low level of light intensities. The natural environment of the plants was in the lower levels of the rainforest where little light could come through. How light intensities could influence on the petiole length and the growth of the plants? It was a common knowledge that leaves were closely related to the function of photosynthesis, because photosynthesis primarily occured in leaf structure of plants. A recently study showed that the shaded plants which lacked nutrients could maintain the ability of absorption from the roots and have the rising lengths and sizes of fine roots along with the stable concentration of nitrogen in leaf parts compared to the plants which were under the sun("Sonia E. Sultan-2000"). The low-light shaded plants were expected to have a normal growth and proper length of petiole the same as its growing environment in the rainforest. If the plants under the high-light intensities, which were not the suitable conditions, could have an increased length of petioles, which was still shorter than the low-light ones, then these plants expressed their ability of response of phenotype from altering genotypes, known as phenotypic plastic, to fit in the unfavourable environment, and ensure their survival.


The subjects for experiment, Pothos aureus plants, which had climbing vines, were being measured the length of petiole, the short stem where the leaves connected to the main stem, under the two different light conditions, low-light intensities(30µEm-2s-1) and high- light intensities (340µEm-2s-1) for around 10 weeks. The plants were displaced in growth chambers at the degree of 22 °C when the plants completed a full light cycle in 16 hours under the sun and 8 hours at dark. The mean (average) of the petiole length and its standard derivation under two light condition and the t-test results such as t-value, the degrees of freedom, p value could be calculated and analysed in the Microsoft Excel after putting the data of petioles length inside.



In the experiment, there were a total of 254 petioles of plants being measured under the two light intensities, high and low light, and each of the conditions had 127 plants. The plants under the low-light had a larger petiole length mean (average) of 55.34 mm than the ones under high-light which was 48.59 mm (figure 1). Also value of standard deviations of the treated plants under the sun was bigger than the treated plants at dark, which had a difference of 2 (figure 1). After, a statistical tests analysis was performed to determine difference of the petioles length of the two groups in the Microsoft Excel. There were 2 statistical hypotheses, Ho and HA. The null hypothesis Ho showed that there was no difference in the means of petiole length under high-light and low-light treated, and HA indicated that there was a difference in the means of petiole length under high-light and low-light treated. The t-value was 3.788 when probability (p-value) was equal or smaller than 0.001 and the degrees of freedom of the two groups was 252 when the total number of petioles measured n was 254 (figure 2). The Critical t- value was around 3.12 when the degrees of freedom was 252. The t-value was greater than the critical t-value from t table for a two-tailed test with p=0.001. The probability determined from the t table was equal and smaller than 0.002 which was less than the cut off probability value of 0.001. Therefore, the null hypothesis (Ho) were rejected which stated the means of both groups were equal, and there was a significant differences between the means of the two groups which were real and could not be attributed to chance alone at a probability level of 0.001.

Discussion and Conclusion:

The results of this experiment was that the statistical test rejected the null hypothesis (Ho) that stated the means of both plants under low-light and high-light were equal. On the other hand, the data analysis sustained the alternative hypothesis (HA) that plants under low-light still had a longer petiole length than the ones under high-light. These results supported the initial research hypothesis that the plants under low-light had a longer length of petiole and faster growth than the plants under high-light and the high-light treated had as obviously slower phenotypic response to the environment than the low-light ones. The plants showed their ability of response of the phenotype to the environmental changes (phenotypic plasticity). The data analysis was able to reach the purpose of the lab, which was to show the diversity of petiole length of plants under different light intensities and therefore displace their phenotypic plasticity to adapt to the environment changes. The reason why there was an evidently longer petiole length in the low-light treated plants was that selection also happened in phenotypic plasticity. The adaptive phenotypic plasticity were more often found in the natural populations where the plants naturally live and growth, because the genetic variation for plasticity in the populations could evolve over time in the response to the natural selection ("Massimo Pigliucci-2005"). Since Pothos aureus Plants were naturally found in the lower level of the rainforest which was basically a low-light place, the plants under low-light had a better ability of phenotypic response to the environment and higher petiole length than the ones under high-light (. There was a study of polygonum persicarial, which was a cosmopolitan annual often found in a wide range habitats with three sites, nutrient rich, nutrient poor in ponds, and half shaded mesic comparing with the species found in the simple and similar habitats. The result showed the ones living in the wide distributed places had a high ability of phenotypic response in terms of light, water and nutrient environment than the other ones. It also revealed that phenotypic plasticity was inclined to find in the species living in the nature, which was a favourable place for them ("Sonia E. Sultan-2000"). The potential problem that were encountered was the plants should have the same length of petiole before performing the experiment, therefore an additional research of the initial length of petiole of the plants should be measured. All in all, the low-light treated plants had a longer petiole length than the high-light treated and both treated plants showed their phenotypic plasticity under various environmental conditions at a certain degree.

Reference Cited:

[1] Tavares, A. and Olaveson, M. 2010. Introductory Biology (BIOL 1020) Lab Manual. University of Ontario Institute of Technology. Oshawa, Ontario.

[2] Crispo, E. 2008, Modifying Effects of Phenotypic Plasticity on Interactions among Natural Selection, Adaptation and Gene Flow. Journal of Evolutionary Biology. 21: 1460-1469.

[3]Sonia, E.S. 2000. Phenotypic Plasticity for Plant Development, Function and Life History. Trend in plant Science Reviews. Vol.5, No.12: 537-542.

[4] Mary, J.W. 1989. Phenotypic Plasticity and the Origins of Diversity. Annual Review of Ecology and Systematics. 20: 249-278.

[5]Anurag, A.A. 2001. Phenotypic Plasticity in the Interactions and Evolution of Species. Science's Compass Review. 294: 321-326.

[6]Massimo, P. 2005. Evolution of Phenotypic Plasticity: Where Are We Going Now? TRENDS in Ecology and Evolution Opinion.Vol.20, No.9: 481-486.



Figure Bar Graph of the Mean Petiole Length under high-light and low-light condition


Summary of t-Test Results


3.788(either +3.788 or -3.788)

The degrees of freedom




Number of petioles measured (n)


Figure t-test results summary

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