Concept explainers
Photosynthesis directly opposes respiration in determining how plants influence atmospheric CO2 concentrations. When a leaf is in the light, both photosynthesis and respiration are occurring simultaneously. The data in the Table were collected from the leaf of a sagebrush plant that was enclosed in a chamber that measures the rate of CO2 exchange. The same leaf was used to collect the data in Interpret the Data in Chapter 7. Respiration is shown as a negative and photosynthesis as a positive rate of CO2 exchange. The net photosynthesis rate is the amount of CO2 (in micromoles per square meter per second) assimilated by the leaf while respiration is occurring; a positive value indicates more photosynthesis is occurring than respiration. The light exposed to the leaf is quantified as the number of photons in the 400 to 700 nm wavelength, the photosynthetic photon flux density (PPFD); 2,000 μmol/m2/s is equivalent to the amount of light occurring at midday in full Sun.
Observation | Photosynthetic Photon Flux Density (PPFD) (μmol/m2/s) | Net Photosynthesis (μmol/m2/s) |
1 | 2,000 | 9.1 |
2 | 1,500 | 8.4 |
3 | 1,250 | 8.2 |
4 | 1,000 | 7.4 |
5 | 750 | 6.3 |
6 | 500 | 4.8 |
7 | 250 | 2.2 |
8 | 0 | -2.0 |
Why is net photosynthesis negative when PPFD is zero? Looking at the respiration data from Interpret the Data in Chapter 7, at what temperature do you think these data were collected?
Source: Data based on unpublished research by Brent Ewers, University of Wyoming.
Want to see the full answer?
Check out a sample textbook solutionChapter 8 Solutions
Biology: The Dynamic Science (MindTap Course List)
- For which kind of plant, and in which condition, would you expect to find leaves with the highest SLA (Specific Leaf Area)? Selected Answer: a shade-Intolerant plant growing in sun Answers: a shade-tolerant plant growing in shade a shade-tolerant plant growing in sun a shade-intolerant plant growing in sun a shade-intolerant plant growing in shadearrow_forwardWhen discussing why the rate of photosynthesis did not increase at higher light intensities, the investigator mentioned the possibility that high light intensities could damage chlorophyll, which would result in a decrease in oxygen production. Which of the following accurately explains the role of chlorophyll in oxygen production during photosynthesis and why damage to chlorophyll would results in lower oxygen production? Select one or more: a. Chlorophyll participates in carbon fixation during the Calvin Cycle. During this process, oxygen molecules are formed. b. Chlorophyll captures energy from sunlight and releases high energy electrons that enter the electron transport chain in the Calvin Cycle. During this process, oxygen molecules are formed. c. Chlorophyll participates in carbon fixation during the light reactions. During this process, oxygen molecules are formed. d. Chlorophyll captures energy from sunlight and releases high energy electrons that enter the electron…arrow_forwardA group of scientists wants to test the effect of different wavelengths of light on plant photosynthesis. They have 3 treatment groups: red light, green light, and no light. They choose red light because chlorophyll has been shown to absorb red light. They choose green light because chlorophyll has been shown to reflect green light. They choose no light as a negative control to examine the rate of photosynthesis in the absence of light. To measure photosynthetic rate, the scientists use sensors to measure oxygen production of plants exposed to the different light treatments. Choose the best scientific hypothesis: O Photosynthesis is a critical process for plants, and it is of great importance that we understand how it is impacted by different wavelengths of light. O If rate of oxygen production is higher under red light than it is under green light or no light, it proves that red light has the largest effect on photosynthesis. O Because chlorophyll absorbs red light, rate of oxygen…arrow_forward
- Propose a hypothesis on how each of these variables affects the production of oxygen from a plant. 1. Increasing light intensity 2.Increasing CO2 levels 3.Increasing temperature 4.How does light intensity affect the rate of photosynthesis?arrow_forwardPhotorespiration causes a number of impacts on a plant. Which of these drives the ECOLOGICAL difference between C3 and C4 plants Question 4 options: Rubisco mistakes Oxygen for CO2 The plant uses energy to convert the toxic product of photorespiration back into something less harmful The plant needs a large number of enzymes to be able to regain the energy invested in the 2 carbon molecule produced by photorespiration None of these explain the difference The plant needs to do gas exchange to remove oxygen and add CO2 to the cell doing photosynthesis to avoid photorespiration.arrow_forwardChloroplasts contain chlorophyll and carotenoids. Chlorophyll directly absorbs light for use in photosynthesis. Carotenoids absorb light and transfer the energy from light to chlorophyll. The efficiency of photosynthesis varies with the wavelengths of the light that illuminates the chloroplasts. In an experiment to study the relationship between the incoming light wavelengths and the chemical reactions of photosynthesis using a species of green algae, a researcher labeled the CO2 supply to the algae with 14C, and the H2O with 18O. Which of the following results is expected? More 14C is found in the algae when it is illuminated by green light than when it is illuminated by blue-violet and red light. More 18O is found in the algae when it is illuminated by green light than when it is illuminated by blue-violet and red light. More 14C is found in the algae when it is illuminated by blue-violet and red light than when it is illuminated by green light. More 18O is found in the algae when…arrow_forward
- A botanist has been examining three plants, measuring the amount of acid in their cells and examining sections of their leaves under the microscope. Numbers in the table are in relative units. Has wreath Plant Acid, day Acid, night FADH2 Ethanol anatomy? A 20 250 No 50 10 10 No 100 1 C 200 10 Yes 100 1 Part A: Identify the kind of photosynthesis being done by each plant. Explain how enzymes contribute to this data. Part B: Decipher the origin of each plant if one is from the Mojave Desert, one is from a sand dune in Florida, and one is from Minnesota, and explain how you deciphered this. BIU E E nswered 13 tv 吕0 F3 000 F2 F4arrow_forwardDiscuss whether it would be more beneficial to improve the light or dark reactions in order to enhance photosynthesis for a future scenario of extreme drought conditions. Please draw sketches to illustrate and include atleast 20 pointsarrow_forwardRubisco can bind with CO2 or 02. When it binds with O2, it "wastes" some of the energy captured from the sun. This reaction is photorespiration and is favored at high temperatures and low CO2:02 ratios. Which of the following strategies should limit photorespiration (select all that apply). Keep stomata closed. Keep stomata open. Physically separate the light and light-independent reactions. Temporally separate CO2 uptake and fixation.arrow_forward
- If you don’t water a plant, it will eventually die. Explain why the absence of water halts photosynthesis. Also, cells that use aerobic cellular respiration, like humans, do not produce ATP at normal levels without oxygen gas. Discuss why this is so.arrow_forwardIn 1770, Joseph Priestley performed a series of experiments to determine the reactants and products of photosynthesis. The diagram below shows the experimental conditions and results of two experiments performed by Priestley, named here as Experiment 1 and Experiment 2. From his experiments, Priestley concluded that plants restore to the air whatever breathing animals and candles remove. Joseph Priestly Photosynthesis Experiments and Results Experiment Results: - candle extinguished (went out) 1 - mouse died Experiment 2 Results: candle continued to burn mouse stayed alive Note: Experiment 1 and Experiment 2 were both performed in the presence of sunlight. The substance produced by the plant in Experiment 2, that keeps the candle burning and the mouse alive is O CO2 O 02 O H2O O C6H1206arrow_forwardRead the article by Taub, 2010 and answer the DQs to Unit -6. What is photosynthesis? Discuss the impact of increasing global CO2 levels on photosynthesis. How different photosynthetic plant type (C3 and C4) will respond to increase in CO2. Which plant will be benefitted more C3 or C4? Why?arrow_forward
- Biology: The Dynamic Science (MindTap Course List)BiologyISBN:9781305389892Author:Peter J. Russell, Paul E. Hertz, Beverly McMillanPublisher:Cengage Learning