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

Exercise 16

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.
Interpret the Data
To explore the relationship between the two variables, it is useful to graph the data in a scatter plot, and then draw a regression line. (a) First, place labels for the dependent and independent variables on the appropriate axes. Explain your choices. (b) Now plot the data points for corn and velvetleaf using different symbols for each set of data, and add a key for the two symbols. (For additional information about graphs, see the Scientific Skills Review in Appendix F and in the Study Area in MasteringBiology.)