Campbell Biology 11th Edition by Lisa Urry,Michael Cain,Steven Wasserman,Peter Minorsky,Jane Reece

Exercise 6

Does Atmospheric Carbon Dioxide Concentration Affect the Productivity of Agricultural Crops Atmospheric concentration of CO₂ has been rising globally, and scientists wondered whether this would affect C3 and C4 plants differently. In this exercise, you will make a scatter plot to examine the relationship between CO₂ concentration and growth of corn (maize), a C4 crop plant, and velvetleaf, a C3 weed found in cornfields.
How the Experiment Was Done Researchers grew corn and velvetleaf plants under controlled conditions for 45 days, where all plants received the same amount of water and light. The plants were divided into three groups, each exposed to a different concentration of CO₂ in the air: 350, 600, or 1,000 ppm (parts per million).
Data from the Experiment The table shows the dry mass (in grams) of corn and velvetleaf plants grown at the three concentrations of CO₂. The dry mass values are averages of the leaves, stems, and roots of eight plants.
Based on the data in the scatter plot, estimate the percentage change in dry mass of corn and velvetleaf plants if atmospheric CO₂ concentration increases from 390 ppm (current levels) to 800 ppm. (a) First draw vertical lines on your graph at 390 ppm and 800 ppm. Next, where each vertical line intersects a regression line, draw a horizontal line to the y -axis. What is the estimated dry mass of corn and velvetleaf plants at 390 ppm 800 ppm (b) To calculate the percentage change in mass for each plant, subtract the mass at 390 ppm from the mass at 800 ppm, divide by the mass at 390 ppm, and multiply by 100. What is the estimated percentage change in dry mass for corn For velvetleaf (c) Do these results support the conclusion from other experiments that C3 plants grow better than C4 plants under increased CO₂ concentration Why or why not