Sample Report On The Effects Of Nh4no3 On Fern Growth
Studies have shown that soil and atmospheric nitrogen concentrations affect the growth potential of fern species across a wide variety of ecosystems. This study evaluates whether high ammonium nitrate concentrations will decrease fern spore growth.
Keywords: ferns, nitrogen, NH4NO3, diversity, growth
Ferns are types of plants that are found in moist environments. They are vascular, seedless plants, which are classified as pteridophyte. Like all vascular plants, they have a specific life cycle called alternation of generations, characterized by alternating diploid saprophytic and haploid gamtophytic phases. A diploid sporophyte phase produces haploid spores by meiosis, and a haploid gametophyte phase produces haploid gametes via mitosis. The diploid sporophyte generation is the dominant generation (Schafer 2013).
Scientists’ have been studying plants for years now, and it is important that they understand different environments in which plants grow best, in order to understand their economic significance. Ferns for example have been studied in multiple environments. Since ferns are photoautotrophic, they are extremely dependent on light. They are also temperature sensitive, meaning their growth depends on specific temperatures. Having this in mind, fern growth was tested in optical temperatures and light but at different ammonium nitrate concentration. It was discovered that nitrogen plays an important role in the reproduction of ferns. Due to ferns inability to use nitrogen directly from the environment, ferns have developed a mutualistic symbiosis with Anabaena bacteria, which allows nitrogen fixation of N2 into organic compounds, ex. NH4NO3 (Melan 1990).
Although organic compounds, which are formed during nitrogen fixation, are important to ferns, increased amounts may cause an adverse outcome (Melan 1990).
Lu et al. (2010) examined the effects of nitrogen concentrations on plant diversity in an old-growth nitrogen-saturated tropical forest. Nitrogen was added to the soil at various concentrations in the course of five years (2003-2005), none of which elicited positive growth response during the study period. However, there was a significant positive correlation between nitrogen concentrations and decreased plant diversity, especially amongst fern species, suggesting that fern growth depends on nitrogen concentrations rather than species competition.
Other studies show that atmospheric nitrogen deposition may also reduce plant diversity across a wide range of ecosystems. Bobbink et al. (2010) evaluated nitrogen concentrations from arctic and boreal systems to tropical forests, and found that nitrogen rich soils prevented the growth of ferns while stimulating the growth of other plants, thus changing the dynamics of interaction between ferns and competing species to the detriment of ferns. The authors expressed concern that nitrogen levels will drive many fern species to extinction as nitrogen levels continue to rise significantly.
Allison and Vitousek (2004) found wide variations in the rate of leaf litter decay between native species and invasive species, with native species decaying at significantly lower rates than invasive species. Thus, invasive species lost nitrogen faster and at larger quantities than native species causing soil nitrogen levels to increase. The rise in soil nitrogen concentration had a positive effect in the growth rate of invasive plants including ferns but suppressed the growth rate of native species.
The goal of this experiment is to understand and discover which environment is beneficial to fern growth. This was done by testing two samples of fern spores, in the presence and absence of ammonium nitrate. It was hypothesized that adding high concentrations of ammonium nitrate will decrease fern spore growth (Melan & Whittier, 1990).
Two petri plates were labeled; one petri plate was labeled as the control group and the other petri plate was labeled as the experimental group. The control petri dish contained regular growth medium and the experimental petri dish was treated with 1% ammonium nitrate. Each plate was then inoculated with three drops of fern spore culture, first by flaming the lips of the glass tube then using a pipette to transfer the fern spores to the petri dishes. The plates were also kept close to the Bunsen burner to prevent any contamination that would be caused by particles falling into the plates.
The spores were then spread out on the petri dishes using a T shaped paper clip and covered immediately to avoid any contamination. This procedure was repeated 5 more times ending up with a total of 12 petri plates. Six petri dishes were control groups and the other six were experimental groups. The plates were then left under adequate lighting and temperature, to maintain the development of the fern spores.
For the next five weeks, using a dissecting microscope, the petri plates were observed every week and their appearance changes were noted. During the final week, the numbers of spores that have germinated on their plates were counted, which was used for statistical data analysis. This included calculating the variance (the F-test), the t-score, and Welch’s approximation. Which provided the significance of the differences between the means of experimental conditions and the control conditions.
Allison S.D. & Vitousek P.M. (2004). Rapid nutrient cycling in leaf litter from invasive plants in Hawaii. Oecoogia 141:612-619. DOI 10.1007/s00442-004-1679-z
Bobbink R., Hicks K., Galloway J., Spranger T., Alkemade, R., Ashmore M., Bustamante M., Cinderby S., Davidson E. , Dentener F., Emmett, J-W. Erisman B., Fenn M., Gilliam F., Nordin A., Pardo L., & De Vries W. (2010). Global assessment of nitrogen deposition effects on terrestrial plant diversity: a synthesis. Ecological Applications 20:30–59. http://dx.doi.org/10.1890/08-1140.1
Lu X., Mo, J., Gilliam F.S., Zhou G. & Fang Y. 2010. Effects of experimental nitrogen additions on plant diversity in an old-growth tropical forest. Global Change Biology 16, 2688–2700, doi: 10.1111/j.1365-2486.2010.02174.x
Melan MA, Whittier DP. 1990. Effects of inorganic nitrogen sources on spore germination and gametophyte growth in Botrychium dissectum. Plant, Cell and Environment 13: 477-482.
Schafer E. Ferns. Salem Press Encyclopedia Of Science [serial online]. January 2013;Available from: Research Starters, Ipswich, MA. Accessed February 25th, 2015.