Photosynthesis and Water Stress
Our long term goal is to be able to assist with the research on photosynthesis physiology (the xanthophyll cycle), but photosynthesis is hard to separate from water physiology. If plants are water stressed, they close their stomates to save water. But this also closes off the only method by which they can absorb CO2 . Without CO2, the plants can't use light energy for photosynthesis, but is still absorbing the light energy. This can lead to photo-oxidative damage.
Water Stress/Drought Research
Over the last 2 semesters we have been experimenting with inducing water stress, but there are several important components of our experimental design and protocols that need to be worked out. This semester, you will work to answer one of these questions so that we can create a drought protocol for use with xanthophyll knockout mutants.
Bio 2.3 students in spring of 2018, developed and implemented research to answer the questions below. In groups they designed an experiment, collected and analyzed the data, presented a poster and wrote up ''Lessons Learned/Next Steps'' document. Individually, they also each wrote a scientific paper.
Science is an iterative process, and we need to pick up where last spring's students left off. You will each need to pick one of these projects to continue, but to help you get started, Here is your assignments.
Assignment : Due 1/28 before class
- Pick two of the Spring 2018 SRJC Drought Research Projects (they are found in the Google Drive)
- For each of the projects, read the scientific paper and the ''Lessons Learned'' (students some times called in Next Steps or Recommendations)
- Write up a summary of the paper that follows this format:
- Research Question: What was their research question?
- Hypothesis: What was their idea/prediction of what would happen?
- Experimental Design: What was their treatment? Dependent and independent variable? How many replications did they have? (You may find the directions for a project proposal helpful to read- it is in the Google Drive as well)
- Results: In 2-3 sentences, summarize their most significant results.
- Lessons Learned : In 2-3 sentences, summarize what changes do they recommend for the next iteration of this experiment.
Original Research Questions:
When can we initiate drought /water stress in our plants?How early in their life can we expose the plants to water stress and still get survival? Equally, how old can the plants be when we begin exposing them to drought and still have an impact on the plants?
- Can we stop watering the plants at some point and imitate late spring dry-down?At what point in their life can we stop watering the plants and have meaningful results, such as survival, flowering, reproduction, etc?
- If the plants are watered at different frequencies, what are the soil moisture levels? What are the soil moisture levels for the regular unPAK protocol? How do those vary over the course of the plants’ growth? How do those compare to more frequent or less frequent watering?
- Is it possible to measure root biomass? Usually people use sandy soil to do this. Is it possible to do this with the unPAK soil? If we use sandy soil, what are the various soil moisture levels with different watering regimes?
- Is it possible to measure specific leaf area (SLA), relative water content (RWC), or wilting with the equipment and money that we have available to us at the JC?
- SLA= leaf area of plant/dry weight of plant
- RWC= (Fresh weight of plant – dry weight of the plant)/ (Turgid weight of plant- dry weight of plant)
- Fresh weight and dry weight are fairly straight forward since we have a drying oven as well as a scale that can weigh very small weights (the dry weight of Arabidopsis is pretty tiny).Turgor weight is a little more work since you have to rehydrate the leaf. Leaf area would be the hardest.