Which of the following is an example of how photoperiodism affects plant ecosystems?
A) Spinach, a long-day plant, flowers in the tropics because the days are so long.
B) Ragweed, a short-day plant, can't flower in the northern US because of the frost in the late summer months.
C) Cockleburs, a short-day plant, can live where there are long flashes of red light at night.
D) Chrysantheums, a short-day plant, bloom in the summer when the days are long.
Answer: B) Ragweed, a short-day plant, can't flower in the northern US because of the frost in the late summer months.