Drafts

Reactive oxygen species and physical damage cause endogenous damage to DNA. This makes DNA oxidized, have crosslinked bases, physical damage, and can lead to polymerase errors. Endogenous damage is repaired by homologous and non-homologous end joining. In homologous end joining, broken DNA uses the sister chromatid as a template to repair the broken strand. This allows for a complete repair without the loss of genetic material. In nonhomologous end joining, there is no sister chromatid available so the broken ends are cleaned up with an exonuclease and snapped back together with ligase.

The snow removal experiment in progress at Harvard Forest is addressing the effects of reduced snowfall in Massachusetts. They are using this experiment to predict how the vegetation would be affected if in the future, the snowfall keeps decreasing in the area. They have plots in which they don’t remove the soil and plots in which they do. So far, they have seen that removing the snow is causing the soil temperatures to drop because the snow is not there to insulate the soil. 

At Harvard Forest, a soil warming experiment is being done to address how the freezing soil is affecting tree growth. They plant young, new trees and artificially warm the soil in certain plots and leave the soil alone in other plots to see how warming the soil would affect tree growth. They also adjust the fertilizer levels in all plots, so certain plots have warmed soil and no fertilizer, others have warmed soil with fertilizer, not warmed soil with fertilizer and a control. This experiment is taking place over years to address long term effects of reduced snowfall in Massachusetts and the colder soil temperatures that result from it. So far, they have seen warming the soil is affecting growth positively.

Prokaryotic DNA replication is THETA replication with one origin and five DNA polymerases. DNA Polymerase III is the main replicating enzyme with a high processivity and a fast 5'-3' polymerase and 3'-5' exonuclease. DNA Polymerase I has a low processivity and a slow 5'-3' polymerase and 3'-5' exonuclease. DNA Polymerase I, II, IV, and V are responsible for DNA repair in prokaryotes.

Nucleic Acid monomers are nucleotides (sugar, base and phosphate), or nucleoside (sugar and base). Ribose is a  5 carbon sugar where the 5^thcarbon is off of ring, and the base attaches to carbon 1. Carbon 2 only has H on DNA and has OH on RNA. RNA is more unstable than DNA because of the OH group. Nucleic acid polymerization removes two phosphates off of carbon 5, remaining phosphate forms phosphodiester bond. There is a 5’-3’ reading direction and synthesis.

The results of herbivore preference followed our hypothesis. Control low fertilized plants were significantly preferred over damage low fertilized plants, and preferred (not significantly, P 0.0844 > 0.05) control high fertilized plants over damage high fertilized plants. Although the result is not 0.05, it is close to significant. If the experiment was replicated, we may be able to determine a significant difference between high fertilized damage and control plants on herbivore preference. Preference between fertilizer groups was not tested for, but damage high fertilized plant leaves had a greater amount of leaf area consumed (0.7668286) over damage low fertilized plants (0.53268571). These results are what was hypothesized, as well fertilized plants have been shown to have less volatile organic compounds found in the leaves and therefore would be preferable to herbivores (Prudic et al. 2005). Our results show that our treatment of mechanical damage and jasmonic acid could be used to deter herbivores in plants receiving a similar amount of fertilizer as our low treatment group, but it is not known how the plants would be affected further in terms of fruit produced and plant success because we did not test for that.

The number of flowers decreased among damage and control groups across fertilizer treatments. As flowers are part of the reproductive system of tomato plants, plants with less flowers could be less successful at reproduction. This would mean our treatment had a negative effect on reproduction, which, if tested for, would be consistent with previous literature (Ziosi et al. 2008; Redman et al. 2001; Koussevitzky et al. 2004). The treatment, although successful on herbivore deterrence, may negatively affect the reproductive success of the plants. This would be another study, but it is important to assess the costs to plant success when considering the benefits of herbivore deterrence.

Herbivore preference was analyzed by a t-test using the proportion of leaf consumed as the response. We analyzed the percent of each of the leaves eaten. Separate t-tests were conducted for the high and low fertilizer dishes. There was a significant difference in low fertilized dishes in preference of damage leaves (M = 0.53268571, SE = 0.06349263) versus control leaves (M = 0.65528214, SE = 0.06625825) conditions; t (27) = -2.1323, P = 0.0422, described in Figure 3. There was also a difference in high fertilized dishes in preference of damage leaves (M = 0.7668286, SE = 0.0507239) versus control leaves (M = 0.64629524, SE = 0.06687644) conditions; t (20) = -1.816, P = 0.0844.

For root biomass, shoot biomass, and number of flowers, a two-way ANOVA was performed for each variable on all fertilizer and damage treatments. There was a significant difference in the root biomass averaged across fertilizer treatments of damage (M = 25.607800, SE = 1.893977) and control (M = 34.944375, SE = 2.296133) conditions; F_{1, 94}= 9.838, P = 0.00228 described in Figure 1. Fertilizer had no significant effect on root biomass for treatment plants (F_{1, 94}= 1.238, P = 0.26877). There was a significant difference in the shoot biomass averaged across fertilizer treatments of damage (M = 145.416000, SE = 6.448853) and control (M = 187.067292, SE = 6.619286) conditions; F_{1, 94}= 20.108, P < 0.0001 described in Figure 2. Fertilizer had no significant effect on shoot biomass between treatment and control (F_{1, 94}= 0.336, P = 0.564). No significant difference was found in the amount of flowers of treatment versus control groups averaged across fertilizer treatment (F_{1, 94}= 0.026, P = 0.8712). Fertilizer had a significant effect on the amount of flowers averaged across damage treatments plants with low (M = 66.125000, SE = 5.807913) and high fertilizer (M= 46.78571, SE = 5.62293) conditions; (F_{1, 94}= 5.450, P = 0.0217). 

Through this experiment, we aim to find how a combination treatment of mechanical damage and application of jasmonic acid, along with differing amounts of fertilizer affects herbivore preferences and plant growth. We will grow 150 tomato plants and randomly assign which plant receives a treatment. Once we have determined that, we will then assign randomly the amount of fertilizer each plant receives. Half of the treatment group plants will receive twice the amount of fertilizer as their counterparts in that group, and half of the control group will be treated the same with fertilizer. Once the plants have grown with treatment for two weeks, we will test herbivore preference. After, we will measure the number of flowers, root biomass, and shoot biomass of each plant to determine growth differences between treatments and fertilizer amounts. With this experiment, we hope to determine if a combination of both mechanical damage and application of jasmonic acid could function as an insecticide for tomato plants.