Passage III

Researchers studied how wildfire smoke affects the germination of Yellow Whispering Bell seeds.

Study 1

Seeds were collected from the plants. Some of the seeds were divided into 9 groups of equal numbers of seeds. The first group of seeds was placed, untreated, on moist, untreated filter paper for germination. Two other groups were treated by exposing them to wildfire smoke, one group for 1 min and one group for 10 min, prior to placement on moist, untreated filter paper for germination. Each of the remaining 6 groups was placed for germination on or in either moist sand, moist filter paper, or water, each of which had been previously treated by exposing it to wildfire smoke for either 1 min or 10 min. The percent of seeds from each group that germinated over the next 2 days is shown in Figure 1.

(Note: All smoke-treated materials were directly exposed to equal concentrations of smoke per unit time.)

Study 2

Study 1 was repeated with more of the collected seeds, except that the treated materials were directly exposed to NO₂ gas (a component of wildfire smoke) instead of wildfire smoke for either 1 min or 5 min. The NO₂ concentration per unit time was the same as that of the wildfire smoke in Study 1 (see Figure 2).

Study 3

Another group of the collected seeds was exposed in air for 10 min. Other groups of the collected seeds were directly exposed to different gases of various concentrations in air for various lengths of time. Each group was then placed on moist, untreated filter paper for germination (see Table 1).