In the life cycle of a bean plant, a mature plant makes flowers, and the flowers make seeds.  In order to grow, the seed must break the tough seed coat. This is called germination. After germination, the plant makes roots in soil and grows until it makes flowers. (see Figure 1).

Figure 1

Students studied how temperature affects the life cycle of one type of plant.

Study

The students filled three planters with four inches of soil.  They planted 10 seeds in each planter. The seeds were planted 1 inch deep and 2 inches apart from each other.  They kept one of the planters at a temperature of 15℃, another planter at 24℃, and the last planter at 33℃. The plants received the same amount of sunlight and water throughout the study.  Each day, the students looked for any changes in the plants. For each planter, the students recorded the number of days:

• until the seed germinated
• from germination until the seedling was 4 inches tall
• from the time the seedling was 4 inches tall until the plant made flowers

They calculated average values for the planters at each temperature and recorded their results in the table.  Note that all the seeds germinated and made flowers.

1.  Identifying when seeds germinate

                    a. At what temperature did the seeds germinate the fastest? 

                    b. How were you able to determine the temperature that caused the fastest germination?

2. How many total days passed before flowers appeared on the plants that were kept at 24°C?

3. Based on the evidence in the study, make a conclusion about how temperature affects the germination of seeds.  Explain what evidence from the experiment supports your conclusion.