Mix the watery environment of Elodea with a pHindicator called phenol red. In the presence of an acid, phenol redwill appear yellow. In the presence of a strong base, phenol redwill appear purple. Intermediate colors correspond withintermediate pH values. Recall that plants use CO2 forphotosynthesis; the concentration of CO2 will determinethe pH of a solution. Plants also produce CO2 as abyproduct of cellular respiration.
- Will a solution with a high concentration of CO2 beacidic or basic? Why? (search on the internet)
- As Elodea uses CO2 during photosynthesis, will thesolution become more acidic or basic? If the solution is also mixedwith phenol red, what color should it become over time?
- Will the concentration of CO2 increase or decreasefor Elodea in darkness? What color will the phenol redindicator show over time?
- Which colors of visible light are used by chlorophyll forphotosynthesis? Which are not?
- Write a hypothesis for how the intensity of light would affectthe photosynthetic rate in Elodea.
