Please see the image. The graph shows that at all temperatures, the presence of the fungus helps the grass to grow better, and the fungus even allows for growth at temperatures at which there is no growth at all without it.
Work Step by Step
To make the bar graph, put plant mass on the y-axis and temperature on the x-axis, and be sure to put the two data points for each temperature (E-, E+) next to one another for easy comparison. Ask yourself if there is a consistent trend for E- vs. E+.