1. Studying the plant-rhizobia mutualism in the classroom – a guided inquiry activity
Sandy

2. Outline Brief background Designing your experiment Scientific methods
Study system
Designing your experiment
Control
Replication
Randomization

3. Not consistent with hypothesis Consistent with hypothesis
Scientific Methods
Observation
Background Research
Hypothesis/Predictions
Question
Experiment
Not consistent with hypothesis
Data analysis
Answer? T
Consistent with hypothesis
Conclusion

4. What happens when you add N in the system?
Background
Soybean
CO2+H2O +light
C6H12O6+O2 N2
NH3
Photosynthesis
Nitrogen Fixation
Rhizobia

5. Fertilizer in agriculture
Background
Fertilizer in agriculture
“….addition of N fertilizer can lead to lower production of nodules in legumes (Rubio Arias et al. 1999; Vargas, Mendes &Hungeria 2000) as well as lower N2fixation rates per nodule (Denison & Harter 1995).”

6. Scientific Questions:
How do rhizobia affect plant growth?
How does nitrogen fertilization affect plant-rhizobia interaction?

7. Hypotheses Question1: How do rhizobia affect plant growth?
Question2: How does nitrogen fertilization affect plant-rhizobia interaction?
Hypothesis1:Rhizobia increase
plant performance
Hypothesis 2: Fertilized plants have fewer nodules than non-fertilized plants.
Hypothesis is an educated answer to the question posed.
It is “a tentative answer to a well-framed question—an explanation on trial” (Campbell and Reece 2008).

8. Predictions Question1: How do rhizobia affect plant growth?
Question2: How does nitrogen fertilization affect plant-rhizobia interaction?
Hypothesis1:Rhizobia increase
plant performance
Hypothesis 2: Fertilized plants have fewer nodules than non-fertilized plants.
Prediction 1: Rhizobia inoculated plants will have greater biomass than non-inoculated plants
Predictions are “what we would expect to happen or what we would expect to observe if this idea were accurate” (Understanding Science 2014b).
Prediction 2: fertilized plants will have fewer nodules than non-fertilized plants.

9. 1) How do rhizobia affect plant growth? How can we test it?
Experiment
1) How do rhizobia affect plant growth? How can we test it? +
Control
Treatment 1 +
Treatment2
-Legume with no rhizobia
--Legume wit rhizobia
-Legume with Fertilizer (Note: This treatment is not necessary to address this specific questions but it tests whether rhizobia and fertilizer provide the same resource.)
Controls are treatments against which manipulations are compared (Karban and Huntzinger 2006). Control group is “a group of individuals or cases matched to an experimental group and treated in the same way as that group, but which is not exposed to the experimental treatment or factor that the experimental group is” (Understanding Science 2014c).
The control and experimental groups must be identical in all relevant ways except for the introduction of a suspected causal agent into the experimental group.

10. Experimental Design
Control
Replication
Randomization

11. Experiment
Replication +
Repetition of a experiment to test the validity of its conclusion + + + As
Replication is the establishment of independent multiple plots or observations within the same treatment or comparison group (Gotelli and Ellison 2004). Replication increases confidence in experimental results. +

12. Randomization + -Assign treatment randomly to an experimental group
-Eliminate researchers’ bias or judgment
Plots and observations should be randomly assigned to the treatment or control group (Gotelli and Ellison 2004) and this can be accomplished by students flipping a fair coin, rolling a fair dice or using a computer algorithm to generate random numbers

13. Plot a prediction graph on your worksheet
???
Plant Size
Predictions in graph.
Control
Rhiz (+)
Nitrogen (+) +

14. 2) How does nitrogen fertilization affect plant-rhizobia interaction?
Experiment
2) How does nitrogen fertilization affect plant-rhizobia interaction? + + +

15. Plot prediction graphs on your worksheet
Predictions:
Predictions
Plot prediction graphs on your worksheet
Plant Size
# Nodules
N (-)
N (+)
N (-)
N (+)

16. Experimental Design Combining Experiment 1&2
Question 1
n = 10
n = 10
n = 10
n = 10
Question 2
Each group: 4 treatments x 2 rep = 8 samples
Class total = 40

17. After 1 month…. Record: Plant height (cm) Number of leaves
Number of nodules
Aboveground biomass
Belowground biomass
3) Plot graphs using the class data
-ruler
-balance (sensitive one)
-tray
-bucket for soil
-microcentrifuge tube
-forceps
-paper bag)
-box to collect all the trays and pots
-scissors
-datasheet