Dr. MacIntosh: aphids can suppress plant defense responses. Thus, infested plants become more susceptible to other aphids.
Mr. Carey: How was that measured??!?!
Aphids were deposited on Leaf #1 and kept fixed on this leaf using cages (“Treatment”). Control plants had empty cages. After a certain amount of time, new aphids were deposited on a different leaf on the same plant as Leaf #1 Let’s refer to this second leaf as Leaf #2 (“Response”). Population growth of the number of aphids on leaf 2, the “response” aphids, was measured. Growth rates were compared between the two treatments (caged aphids and empty cages). The result indicated that “response” aphids had more reproduction when they were deposited on plants that already had aphids.
Next Jyll and Jakk hypothesized:
Jyll:
Aphids had a saliva component (“effector”) that can block defense responses. Therefore, more aphids or more time on the plant results in more effector being introduced in the plant. Therefore, she believes the rate at which an aphid population on leaf #2 grows is related to the total number of aphid hours spent on leaf #1.
Jakk:
Once aphids are present, the plant’s defenses are compromised. Therefore, the rate the aphid population on leaf #2 grows is strictly a function of time. He believes the growth in aphid population on leaf #2 is related to the presence of aphids on leaf #1 not the number of aphids on leaf #1.
Student instructions:
Create a report for the scientist at Iowa State that shows differential equations that model each of these views with the justification for each. Show how to solve these differential equations, create possible tables of values the scientist at Iowa State could use to determine which person’s thinking is more descriptive. Photo credit: Pixabay.com 5