Lab 1 Reading Questions
1. What are the main questions addressed by this research? Briefly summarize the relevant past
research and the ideas that lead to this question.
The main question being addressed is: Why and how is partner choice from M. truncatula for
rhizobia decided and are there plant sanctions involved in determining efficient symbiosis
partners. Previous studies have shown that this mutualism must be caused by partner choice
based on symbiotic efficiency. Plant sanctions have been shown to exist in soybeans and yellow
lupin nodules (Gubry-Rangin et al. 2010).
2. What hypothesis did the authors test? Explain how it is related to the author’s question.
Sanctions and partner choice are the mechanisms of which M. truncatula ensures effective
symbiosis. So, this hypothesis is directly related to their main question because it is exploring
the role of sanctions and partner choice for symbiosis.
3. How did the authors test their hypothesis? Briefly summarize their methods.
A single line of M. Truncatula was allowed to grow for a week in a split-root system. Each plant
system then had either the same rhizobia strain added in each half (single-inoculation), or a
mixture of two rhizobia strains (mixed inoculation), and potassium nitrate was removed. After
growing for seven weeks, the following measurements were taken for each half plant system:
number of nodules, total fresh biomass, dried stem weight, and total viable bacteria inside the
nodules was measured.
4. What were the Main results of their experiment?
One rhizobia strain was n