The Effects of Mycorrhizae Fungus on the Growth of Lupine




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The Effects of Mycorrhizae Fungus on the Growth of Lupine (Lupinus)
David Truong

Department of Biological Sciences

Saddleback College

Mission Viejo, CA 92692
The objective of this study was to determine if mycorrhizae fungus has an effect on lupine, Lupinus, in different environments. In this experiment, thirty lupine seeds were divided into two groups and placed into different environments. It was expected that mycorrhizae would have a low effect or no effect at all on the growth of the lupine seeds. Average height of the control group had an average of 1.4533± 0.062(±S.E.) centimeters and the experimental had an average of 0.0 ± 0.0(±S.E.) centimeters. Statistical analysis showed that there was a significant difference between the control and experimental group (P-value = 6.74E-13). This experiment proved the hypothesis that mycorrhizae bacteria would not have an effect on lupine plants.

Introduction

Plants have a major role in the Earth’s ecosystem from providing shelter to organisms to oxygen for us to breathe. Like every living organism, plants have to gain nutrients and other necessities in order to survive. With that knowledge, plants have many different profiles when it comes to obtaining their nutrients in order for them to survive and grow. Many plants take on forms of taking in nutrients from the soil such as phosphorus or nitrogen which are both important in plant growth and survival. Some plants use nitrogen fixation to get nitrogen from the air into their roots while others use fungus to absorb nutrients around their surroundings. With the Earth’s atmosphere containing eighty percent of nitrogen gas (N2) which many living organism cannot use by it because it is unstable by itself to many organisms. Combined with hydrogen gas (H2) it creates ammonia (NH3) which living organisms use to create proteins and other nitrogen components to live (Johnson et al., 1987). Process where unstable N2 is changed into useful NH3 is called nitrogen fixation. With about 200 to over 500 different kinds of species in its own genus, most lupine plants can fix N2 into NH3 by nitrogen fixation (Ainouche and Bayer, 1999). The lupine roots would get infected by the Rhizobium bacteria and end up creating nodules in the lupine plant where the nitrogen fixation would take place. This is where the plant and the bacteria communicate chemically to form the nodules (González-Sama et al., 2004). Plants also need to gain nutrients from the soil that they reside in. Some plants use fungus, such as Mycorrhizae, to aid them in the gain of water and nutrients from the surrounding. Plants are sometimes incapable of absorbing minerals such as phosphate ions, but with the aid of the mycorrhizae, they are able to reach the ones that are immobilized in the soil for the plants that they colonize in. The mycorrhizae in return gain direct access to carbohydrates that are produced from the plant during photosynthesis. The effect of mycorrhizae has on plants varied depending on the plant that the mycorrhizae’s host plant (Bray, 2003).

Materials and Methods

Thirty lupine seeds, nitrogen soil, and thirty pots were obtained from Lowe’s of Westminster, Westminster, CA on eighth day of October 2009. The thirty lupine seeds were divided into two groups, fifteen each, and were placed into two environments of nitrogen soil. Nitrogen soil was divided equally throughout the thirty pots with the aid of a measuring cup. Half a tablespoon of mycorrhizae fungus, obtained from Saddleback College Biology Lab, Mission Viejo, CA, was placed into fifteen of the pots, containing nitrogen soil, one inch into them. The two groups were labeled to determine the difference between the group containing mycorrhizae and the group without. The plants were kept in a greenhouse at Natasha Nguyen’s house, Lake Forest, CA. The plants were watered every other day and observed to see any kind of growth above the soil. As the plants grow above the soil, they are measured to see their growth and compared next to each other.

Results


A one-tailed t-test was run on the numbers of total heights of each group and the result came out to be that there was a significant difference between the control and experimental group. A graph showing the average height between the two groups is shown in Figure 1.

Figure 1 - Bar graph displaying the height means for the control and experimental groups. Error bars indicate standard deviation. Control had an average of 1.4533± 0.062(±S.E.) centimeters and the experimental had an average of 0.0 ± 0.0(±S.D.) centimeters, N=15.

Discussion

The experiment came out to support the hypothesis that the group that did not contain mycorrhizae fungus would grow more than the group containing the fungus. However there could have been unaccounted variables in the experiment causing the experiment to fluctuate. A factor that could have been caused an effect could be the ration proportion of the mycorrhizae to the lupine seed and if it was enough to inhibit the seed at all. With lupine plants they undergo nitrogen fixation to help fertilize their soil and allow them to be tolerant towards the change or barren and poor quality soil, so for that, mycorrhizae may have a low or no effect at all on the lupine plants (Bray 2003). But for mycorrhizae to be in the environment of a plant that regulates its growth through nitrogen fixation would be a factor in its survival and growth. Mycorrhizae could have been blocking a lot of the nitrogen soil from the lupine plant to have access to causing it to have any kind of growth at all. The mycorrhizae being under the lupine seed may be the reason why the lupine seed could not have access to the nitrogen to undergo nitrogen fixation and allow it to grow as the control group did.

Acknowledgements

I would like to thank Natasha Nguyen for the provision of her greenhouse and weight balance; also I would like Professor Teh and Dr. Huntley in the provision of the mycorrhizae fungus.

Literature Cited

Ainouche, Abdel-Kader, Randall J. Bayer. (1999) “Phylogenetic relationships in Lupinus (Fabaceae: Papilionoideae) based on internal transcribed spacer sequences (ITS) of nuclear ribosomal DNA.” American Journal of Botany. Vol. 86, No. 4, pp. 590-607

Bray, Sarah R., Kaoru Kitajima and David M. Sylvia. (2003) “Mycorrhizae Differentially Alter Growth, Physioogy, and Competitive Ability of an Invasive Shrub.” Ecological Applications, Vol. 13, No. 3, pp. 565-574

González-Sama, Alfonso, M. Mercedes Lucas, María R. de Felipe and José J. Pueyo (2004) “An Unusual Infection Mechanism and Nodule Morphogenesis in White Lupin (Lupinus albus).” New Phytologist, Vol. 163, No. 2, pp. 371-380

Johnson, D. N., B. Liu, B. L. Bentley. (1987) “The Effects of Nitrogen Fixation, Soil Nitrate, and Defoliation on the Growth, Alkaloids, and Nitrogen Levels of Lupinus succulentus (Fabaceae).” Oecologia. Vol. 74, No. 3, pp. 425-431

Marvel, J. Deborah, John G: Torrey, Frederick M. Ausubel (1987) “Rhizobium Symbiotic Genes Required for Nodulation of Legume and Nonlegume Hosts.” Proceedings of the National Academy of Sciences of the United States of America. Vol. 84, No. 5, pp. 1319-1323

Sawada, H., L. David Kuykendall, John M. Young. (2003) “Changing concepts in the systematics of bacterial nitrogen-fixing legume symbionts.” J. Gen. Appl. Microbiol.

Waughman, J. G., D. J. Bellamy. (1980) “Nitrogen Fixation and the Nitrogen Balance in Peatland Ecosystems.” Ecology. Vol. 61, No. 5, pp. 1185-1198



Wilson, Gail W. T., David C. Hartnett, Melinda D. Smith and Kerri Kobbeman. (2001) “Effects of Mycorrhizae on Growth and Demography of Tallgrass Prairie Forbs.” American Journal of Botany, Vol. 88, No. 8, pp. 1452-1457


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