How woulf you interpret tge change in daily patterns of co2 exhnage during the period between days 4 and 10
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The net photosynthetic production rate (NPP) is the difference between the rate of carbon fixation by photosynthesis (P) and the respiration rate (R). Each of these rates can be expressed in units of grams of carbon per day (gC/d). Vascular plants convert fixed carbon that is not released as carbon dioxide into biomass with a growth rate (G). A. Draw areas within the box to represent the rates of growth (G) and respiration (R) to show the limit of each on the overall growth rate. The area of the box represents the rate of photosynthesis (P). When the dependences on temperature of photosynthetic and respiration rates of a vascular plant are measured, the results depend on the species but have the general form shown in the figure. In these measurements, the temperature is maintained for several hours. The plant is then returned to 25 °C for several hours before the next set of measurements is made at a slightly higher temperature. B. Evaluate these data to approximately predict the quantitative effect on the NPP and free energy availability in a deciduous forest ecosystem with a $3-5-^{circ} mathrm{C}$ increase in temperature. This is the expected temperature increase by the year 2100. Assume the current average summer temperature of the forest ecosystem is $25^{circ} mathrm{C}$ In other experiments, rather than returning the plants to $25^{circ} mathrm{C}$ the plant is grown for several days at a constant higher temperature. Under these conditions, the maximum photosynthetic rate shifts towards the temperature of the new growing conditions. However, there is little change in the temperature dependence of respiration rate. This is referred to as temperature acclimation, an effect of great importance to predictions of future climate change. C. Pose two scientific questions whose pursuit could lead to either an improved understanding of the mechanisms of temperature acclimation or improvements in models of atmospheric carbon dioxide concentrations that control temperature. According to the graph, growth is predicted to increase when acclimation is taken into account and the average temperature increases of Earth’s surface increases by the expected $3-5^{circ} mathrm{C}$ . Growth enhancement may be reduced, however, if respiration increases more rapidly than photosynthesis, particularly under periods of drought and stress. Thus, climate warming may result in positive, negative, or potentially no effect on the free energy availability in forest ecosystems. D. In the figure below, the response to temperate change in terms of the rates of photosynthesis and respiration are sketched as a function of time from the very short-term (seconds) to the longer-term (decades) changes. Acclimation in the laboratory occurs in days. Analyze the graphs; in the box bounded by a dashed line, sketch curves for responses of both processes beyond the acclimation observed in the laboratory that are consistent with a neutral effect on free energy availability and provide your reasoning. E. Analyze the long-term effect of a rate of respiration that exceeds the rate of photosynthesis in terms of dynamic homeostasis.
Adi S.
The net photosynthetic production rate (NPP) is the difference between the rate of carbon fixation by photosynthesis (P) and the respiration rate (R). Each of these rates can be expressed in units of grams of carbon per day (gC/d). Vascular plants convert fixed carbon that is not released as carbon dioxide into biomass with a growth rate (G). A. Draw areas within the box to represent the rates of growth (G) and respiration (R) to show the limit of each on the overall growth rate. The area of the box represents the rate of photosynthesis (P). When the dependences on temperature of photosynthetic and respiration rates of a vascular plant are measured, the results depend on the species but have the general form shown in the figure. In these measurements, the temperature is maintained for several hours. The plant is then returned to 25 °C for several hours before the next set of measurements is made at a slightly higher temperature. B. Evaluate these data to approximately predict the quantitative effect on the NPP and free energy availability in a deciduous forest ecosystem with a $3-5-^{\circ} \mathrm{C}$ increase in temperature. This is the expected temperature increase by the year 2100. Assume the current average summer temperature of the forest ecosystem is $25^{\circ} \mathrm{C}$ In other experiments, rather than returning the plants to $25^{\circ} \mathrm{C}$ the plant is grown for several days at a constant higher temperature. Under these conditions, the maximum photosynthetic rate shifts towards the temperature of the new growing conditions. However, there is little change in the temperature dependence of respiration rate. This is referred to as temperature acclimation, an effect of great importance to predictions of future climate change. C. Pose two scientific questions whose pursuit could lead to either an improved understanding of the mechanisms of temperature acclimation or improvements in models of atmospheric carbon dioxide concentrations that control temperature. According to the graph, growth is predicted to increase when acclimation is taken into account and the average temperature increases of Earth’s surface increases by the expected $3-5^{\circ} \mathrm{C}$ . Growth enhancement may be reduced, however, if respiration increases more rapidly than photosynthesis, particularly under periods of drought and stress. Thus, climate warming may result in positive, negative, or potentially no effect on the free energy availability in forest ecosystems. D. In the figure below, the response to temperate change in terms of the rates of photosynthesis and respiration are sketched as a function of time from the very short-term (seconds) to the longer-term (decades) changes. Acclimation in the laboratory occurs in days. Analyze the graphs; in the box bounded by a dashed line, sketch curves for responses of both processes beyond the acclimation observed in the laboratory that are consistent with a neutral effect on free energy availability and provide your reasoning. E. Analyze the long-term effect of a rate of respiration that exceeds the rate of photosynthesis in terms of dynamic homeostasis.
A team of scientists grew groups of birch trees in greenhouses under four conditions. ‐n.s.‐ means not significant. a) The top graph shows total photosynthesis over a spring and summer. If the observed pattern occurs in the field as well (that is, not just in greenhouses) would the consequence be a positive feedback or negative feedback on climate change? (State your answer and explain in 3 sentences or less.) b) The bottom graph, from the same experiment, documents the date the trees dropped their leaves in the Autumn. Does the effect documented in the graph tend to strengthen or weaken the feedback you identified in Part (a)? (State your answer and explain in 3 sentences or less.) c) The scientists were puzzled that warming + CO2 had no greater effect than CO2 alone. Their hypothesis is that the amount of CO2 a birch tree can absorb over spring and summer is being limited by nitrogen. If you were to run your own version of the experiment to test the nitrogen-limitation hypothesis, what treatment groups would you add? (State your answer and explain in 3 sentences or less.)
Suman K.
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