Biology - This is Crucial to Doing Well on Lab Reports Part 1

The Effects of the Fungus Phytophthora infestans on Bean, Pea, and Corn Plants Introduction Originating in Peruvian- Bolivian Andes, the potato (Solanum tuberosum) is one Sections of reports are clearly labeled. of the world’s four most important food crops (along with wheat, rice, and corn). Cultivation of potatoes began in South America over 1,800 years ago, and through Background information is present. the Spanish conquistadors, the tuber was introduced into Europe in the second half of Purpose of experiment is clearly stated. Ireland, and the country’s economy heavily relied on the potato crop. In the middle of Latin names are italicized the 1600s. By the beginning of the 18th century, the potato was widely grown in the 19th century, Ireland’s potato crop suffered widespread late blight disease caused by Phytophthora infestans, a species of pathogenic plant fungus. Failure of the potato crop because of late blight resulted in the Irish potato famine. The famine led to Proper in-text citation format is used (Name- Year system). widespread starvation and the death of about a million Irish. The potato continues to be one of the world’s main food crops. However, P. infestans has reemerged in a chemical-resistant form in the United States, Canada, No direct quotations are used. Citations are paraphrased and the sources are given in parentheses. Mexico, and Europe (McElreath 1994). Late blight caused by the new strains in costing growers worldwide about $3 billion annually. The need to apply chemical fungicides eight to ten times a season further increases the cost to the grower (Stanley 1994; Stanley 1997). P. Infestans is thus economically important pathogen. P. infestans, which can destroy a potato crop in the field or in storage, thrives in warm, damp weather. The parasitic fungus causes black or purple lesions on a potato plant’s stem and leaves. As a result of infection by this fungus, the plant is unable to photosynthesize, develops a slimy rot, and dies. P. Infestans similarly infects the tomato plant (Lycopersicon escultentum). The purpose of the present experiment was to determine the effects of P. Infestans on plant height, number of leaves, leaf angle, and chlorophyll content of three agriculturally important plants: Phaseolus variety long bush beans, Zea mays (corn), and Pisum sativum (peas). Symptoms of fungal infection were assumed to be similar to that in potatoes. Material and Methods M&M are always written in past tense. Phaseolus variety long bush bean, Zea mays (corn) and Pisum sativum (pea) seeds were soaked overnight in tap water. Fifteen randomly chosen seeds of each species were planted 1 cm beneath the surface in three separate trays containing 10 cm of Sufficient detail is given to allow the reader to repeat the experiment. potting soil. Another set of trays, which was to be the control group, was prepared in the same fashion. All the experimental plants were placed in one fume hood, and all the control plants were placed in relative positions in another fume hood in the same room. The plants were exposed to the ambient light intensity in the hood (153 fc) and air current 24 hrs a day, and were watered lightly daily. The plants were allowed to germinate and grow for 18 days. Phytophthora infestans on potato dextrose agar was obtained from Carolina Biological Supply House. At day 10 of the plant regime, pieces of agar on which the fungus was growing were transferred to L-broth. L-broth consisted of 5 g yeast extract, 10 g tryptone, 1 g dextrose, and 10 g of NaCl dissolved in distilled water, and adjusted to pH 7.1, to make 1 L of medium. The medium was sterilized before adding to the fungal culture. After 4 days in L-broth, 6 mL of the fungal culture was injected into the soil around the roots of each 18-day old plant. 6 mL of L-broth without P. infestans was injected into the soil of the control plants. All plants were then allowed to grow for another 8 days. Every other day after treatment with P. infestans, plant height and number of leaves were measured for both the control and the experimental plants. Plant height was measured from the soil to the apical meristem of the plant. Leaf angle (as shown in Figure 1) of the largest, lowest leaf on each plant was measured three times, once prior to injection, once 4 days after injection, and once 8 days after injection. Leaf angle was measured in order to determine if P. infestans causes wilting in the three plant species. In addition, the plant was examined visually for the presence of any leaf spots. Figures that explain the methodology may be included in M&M section. Chlorophyll assays were performed on one plant from each tray prior to injection and on the eighth day after injection. For each chlorophyll assay, the leaves of the plant were removed from the stem. For each 0.1 g of leaves, 6.0 mL of 100% methanol were used. The leaves were thoroughly ground half of the methanol with a pestle in the mortar. The leaves were ground again after the rest of the methanol was added. Extraction of the chlorophyll was allowed to proceed for 45 min at room temperature. Then the suspension was gravity filtered through filter paper to remove the leaf parts. The absorbance of the filtrate was measured with a Spectronic 20 spectrophotometer at 652 nm and 665.2 nm. The absorbance values were converted to relative chlorophyll units using the following equation derived by Porra and colleagues (1989): Subscripts are made properly. Total chlorophyll (a and b) = Dilution factor x [22.12A652nm + 2.71A665.2nm (mg/l)] x Volume of solvent (L) / Weight of leaves (mg) Results P. infestans- treated plants and the control plants had similar growth patterns (Figure 2). Both the experimental and control pea and corn plants grew at a constant, but very slow rate over the eight day test period. The control bean plants were taller on average than the experimental bean plants throughout most of the experiment. Both groups showed the same growth pattern, however, with rapid growth occurring from day 18 to 24 (0 to 4 days after injection), followed by slower growth to the end of the experiment. Results section must contain a text in which the author presents each figure and table to the reader. Reference is made to the next figure in the sequence and the important results are described. Figure is large enough to read key and axes easily. Axes have proper spacing. Points and Lines on curve are dark and can be easily distinguished from each other. Units are given in parenthesis after the axis label (where applicable). Figure caption is located below figure. Figure title is not simply a repeat of “y-axis vs. x-axis label.” As plant height increased, the average number of leaves on all of the plants also increased over the measurement period (Figure 3). There is an uncharacteristic decrease in the number of leaves of pea plants treated with P. Infestans from day 18 to 20 (0 to 2 days after injection), but this is probably due to counting error. There was a general decline in average leaf angle of all the plants over the first four days after injection with P. infestans (Figure 4). The plants did not follow this pattern over the second half of the experiment, however the leaf angle of the experiment bean group increased by 28⁰ , while that of the control bean group only increased by about 3⁰ . The leaf angle of control pea plants increased significantly (33⁰ ) , while that of the experimental pea plants decreased 4⁰ . The leaf angle of the control corn group decreased 0.5⁰ , while that of the corn experimental group showed a much sharper decline of 24⁰ . Figure Number sequence is correct. Reference is made to the next figure and the important information is described. Symbols (such as⁰) are typed using word processing software. There was also no difference between the experimental and control groups with regard to chlorophyll content. There was slight increase in chlorophyll content from day 18 to 26 (0 to 8 days after injection) in the corn plants (Table 1). For the bean group, there was a large decrease in chlorophyll content, 0.1 relative chlorophyll units, which did not seem to agree with the general appearance of the plants. There may have been some error when this assay was carried out. There was little change in chlorophyll content for that pea group. Finally, there was no evidence of any brown, or black leaf spots symptomatic of P. infestans infection. Table is numbered properly Table caption is placed above the table. Scientific Notation is used correctly. It is preferable to leave extra space at the bottom of the page, rather than to split a table across the page. Discussion P. infestans did not affect the plant height, leaf angle, number of leaves, and chlorophyll content of Zea mays, Pisum sativum, or Phaselous. Symptoms of infection are the presence of brown or black spots (areas of dead tissue) on leaves and stems, and, as the infection spreads, the entire plant becomes covered with a cottony film (Stanley 1994). None of the experimental plants exhibited these symptoms. There may be several reasons why P. infestans did not affect the plants in this study, one reason is that the Lbroth culture of P. infestans may not have contained zoospores of the fungus. Zoospores are motile spores that can penetrate the host plant through the leaves and soft shoots or through the roots (Stanley 1994). Zoospores are usually produced in wet, warm weather conditions (Ingold and Hudson 1993). If the L-broth culture did not contain any zoospores, then these conditions may have prevented P. infestans from attacking the roots and shoots of the plants. In order to determine if the problem was lack of zoospores, first the L-broth culture could be examined microscopically for presence of zoospores. Second, the P.infestans plants could be watered with different quantities of water to determine if the fungus requires wetter soil for zoospore Results are summarized or briefly restated in the Discussion section as the Explanations for results are given. References are used to support explanations. Ways to test explanations may be offered. Frequent use of references is made to support explanations. Whenever possible, use primary references (journal articles, conference proceedings, collections of primary articles in a book). Avoid internet sources (may be unreliable). production and motility. Another reason why P. infestans may not have affected the plants is that this species of fungus may be specific to potato (Solasnum tuberosum) and tomato (Lycoperisicon esculentum) plants (Stanley, 1994), which both belong to the nightshade family (Solanaceae). In contrast corn belongs to the grass family (Gramineae) and peas and beans are legumes (Leguminosae). It may be that these plant families are not susceptible to P. infestans, which has a very limited host range (Stanley 1994). Non-susceptible plants have been shown to have defense mechanisms that prevent P. infestans from infecting them (Gallegly 1995). Further research is required to determine if P. infestans really cannot infect corn, pea, and bean plants. Goth and Keane (1997) developed a test to measure resistance of tomato and varieties to original and new strains of P. infestans. Their experiments involved exposing the experimental plants’ leaves directly to the fungus, and this method could perhaps be tested on corn, peas, and bean leaves as well. Citing the literature through in-text citations and Literature cited section of the Lab report. Name-Year System In-TEXT CITATIONS You should have in-text citations in introduction, methods, and discussion sections of your report. 1 author 3 or more authors 2 authors 1 author Gametophytes of the tropical fern Ceratopteris richardii (C-fern) develop either as males or hermaphrodites. Their fate is determined by the pheromone antheridiogen (Naf 1979; Naf et al. 1975). Banks et al. (1993) found that gametophytes respond to antheridiogen only for a short time between 3 and 4 days after inoculation. Although the structure of antheridiogen is unknown, it is thought to be related to the gibberellins (Warne and Hickok 1989). Gibberellins are a group of plant hormones involved in stem elongation, seed germination, flowering, and fruit development (Treshow 1970). CORRESPONDING FULL REFERENCES Journal article Banks J, Webb M, and Hickok L. 1993. Programming of sexu al phenotype in the homosporous fern Ceratopteris richardii. Inter. J. Plant Sci. 154(4): 522-534. Article in book Naf U. 1979. Antheridiogens and antheridial development . In: Dyer AF, editor. The Experimental Biology of Ferns. London: Academic Press. pp. 436-470. Journal article Naf U, Nakanishi K, and Endo M. 1975. On the physi ology and chemistry of fern antheridiogens. Bot. Rev. 41(3): 315-359. Book Journal article Treshow M. 1970. Environment and Plant Response. New York: McGraw-Hill. 250 p. Warne T and Hickok L. 1989. Evidence for a gibberellin biosynthetic origin of Ceratopteris antheridiogen. Plant Physiol. 89(2): 535-538. Citing the Lab manual Garcia RS, Spikes DA, and O’Neal MH. 2020. Fundamentals of Scientific Inquiry in the Biological Sciences I. Stony Brook: Stony Brook University. Accessed 2019 September. Citing online sources Cite online Journals as a Journal article (see above) Cite online Textbooks as a book (see above) and include the and the accession date. Citing other online sources: Authors (Last name space first and middle initials- see above) or Organizational Name or Company Name. Date of the source (date it was last updated or copyright date). Title. Accessed Date as Year Month Day. Barrett KE, Barman SM, Boltano S, and Brooks HL. 2016. Ganong’s Review of Medical Physiology, 25th ed. China: McGraw-Hill Education. 768p. Accessed 2019 February. SGD Wiki. 2013. General topics: General S. cerevisiae information. Accessed 2019 January. Lab Report Writing Timeline Time Frame Day 1 Day 2-3 Day 4 Activity Complete laboratory exercise. Write first draft of laboratory report. Proofread and revise first draft (hard copy). Give first draft to a peer for review in your presence only or go to the writing center. Rationale It’s fun. Besides, you need data to write about. The lab is still fresh in your mind. You also need time to complete the subsequent tasks before the due date. Always take a break after writing the first draft and before revising Your peer reviewer is a sounding board for your writing. He/she will give you feedback on whether what you intended to write actually comes across in the text. You may wish to alert your peer reviewer to concerns you have about your paper (see “Look at the Big Picture” in Chapter 5 Knisely SBU available in Lab/BLC). A note of caution: be careful not to share your document Day 5 Arrange to meet with your reviewer after he/she has had time to review your paper (“writing conference”). with classmates. If your work is copied by another student, Stony Brook considers you an accomplice to academic dishonesty. An informal discussion is useful for providing immediate exchange of ideas and concerns. Peer reviewer reviews laboratory report. The peer reviewer should review the paper according to two sets of criteria. One is the conventions of scientific writing as described in “Scientific Paper Format,” and the other is the set of questions in “Get Feedback” in Chapter 5. Hold writing conference during which the reviewer returns the first draft to the writer. An informal discussion between the writer and the reviewer is useful to give the writer an opportunity to explain what he/she intended to accomplish, and for the reviewer to provide feedback. Revise laboratory report Based on your discussion with your reviewer, revise as necessary. Remember that you do not have to accept all of the reviewer’s suggestions. Your instructor wants to know what you’ve learned (we never stop learning either!). Day 6 Days 6-7 Day 8 Hand in final copy to instructor. Refer to Knisely SBU edition Chapter 5 for information on “Numbers, abbreviations, punctuation, clarity, grammar, word usage, and spelling.” A copy of the Knisely SBU edition is available for use in the BLC or your Lab. Things to Avoid Avoid lengthy descriptions of routine procedures. EXAMPLE: To make the dilution, a micropipettor was used to release 45, 90, 135, and 180 µl of bovine serum albumin (BSA) into four different test tubes. To complete the dilution, 255, 210, 165, and 120 µl of TBS was added, respectively. REVISION: The following concentrations of BSA were prepared for the Bradford assay: 300, 600, 900, and 1200 g/ml. Avoid giving "previews" of your data analysis inthe Materials and Methods section. Consider the following passage: EXAMPLE: A graph was plotted with Absorbance on the y-axis and Protein concentration on the j-axis. An equation was found to fi t the line, then the unk nown protein absorbances that fell on the graph were plugged into the equation , and a concentration was found. REVISION: Delete this entire passage. But you should state how the data was analyzed if you used a software program or applied a particular statistical software program or need to report level of significance. Eliminate unnecessary introductions. EXAMPLE: Table 1 shows the effects of light and hormones on the germination of light-sensitive lettuce seeds. One group of seeds was treated with ABA and left under a fluorescent light, while another group received GA in the dark. It can be seen that the majority of the seeds (92.5%) germinated in the light, but fewer germinated in the light when ABA was present. The first sentence of this passage is unnecessary, because it says nothing substantive about the data contained in Table 1; instead, it describes the layout of the table, which needs no description. The second sentence is also unn ecessary, because it restates the material s and methods, but says nothing about the results. The first part of the third sentence ("It can be seen that") is simply verbiage. Avoid other unnecessary introduction s such as : Table 1 shows the effects of light and hormones on germination of light-sensitive lettuce seeds. It was foun d that... Whe n th e test plate s were observed and counted,.. . There is also a general trend where... It ca n be determined that... Table 1 shows that there is a relationship between hormones and seed germination. (What is the relationship?) Formatting Figures and Referencing Figures or Tables in the Results section (Knisely SBU figures 4.1 and 4.2) Formatting Tables Formatting Figures