1. Analysis of preserved leaves shows that the density of stomata per unit area
ID: 191298 • Letter: 1
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1. Analysis of preserved leaves shows that the density of stomata per unit area of leaf has decreased over the past 200 years. Suggest a hypothesis for this decrease? 2. In an experiment, chloroplasts were first made acidic by soaking them in a solution at pH 4. After the thylakoid space reached pH 4, the chloroplasts were transferred to a basic solution at pH 8. The chloroplasts then made ATP in the dark. Explain this result. Most cyanobacteria are photoautotrophs. Some bacteria are called photo heterotrophs. What does your group think this means in terms photosystem capability and production? Explain. Would you think photo heterotrophs represent a more ancestral group of photosynthetic organisms or a more recent group that evolved after the photoautotrophs? 3. 4. Some plants with genetic defects are unable to photo respire. These plants end up being damaged under intense light. Researches identify this as evidence that photo respiration is a protective mechanism in plants. Why might a disabling of the photo respiratory pathway lead to cell damage and how might the process of photorespiration mitigate this damage?Explanation / Answer
1. The stomatal density per unit area of the preserved leaf is decreased because of the variation in environmental factors such as sunlight and deficit water availability.
2. The synthesis of ATP by chloroplast in dark was showed by André Jagendorf. According to him, the formation of ATP in chloroplasts are similar to those for oxidative phosphorylation as here, protons are released into the thylakoid lumen or uptaken from the stroma, generating a proton gradient. Thus a gradient is maintained because the thylakoid membrane is importantly impermeable to protons.The thylakoid space turns acidic, the pH becomes 4. The light-induced transmembrane proton gradient is about 3.5 pH, energy present in the proton gradient, called the proton-motive force.Thus the proton-motive force generated by the light reactions is converted into ATP by the ATP synthase of chloroplasts.
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