Many tree seeds are dormant; they fail to germinate even under favorable conditions. The seeds of southern pines are often dormant and usually benefit from stratification. Seeds are imbibed for 24 h in aerated water at room temperature and placed in plastic bags in a cool room at 1 to 4 ° C for 30 to 90 d. Dormancy is removed by this treatment and the seeds germinate rapidly and uniformly even under less than ideal conditions. Nursery managers prefer to work with non-dormant seeds because they produce uniform stands of healthy seedlings. A seed that germinates vigorously will produce a healthy vigorous seedling that will resist diseases, insects and abiotic stresses.

Methods: Seeds will be stratified for 0, 5 and 35 d and germinated at day/night temperatures of 30/20 ° C and 20/10 ° C on moist paper. Each crew will count 25 seeds per stratification treatment and germination temperature. Before stratification the seeds will be imbibed in a cup of tap water for 24 h. Start the 35 d treatment first, then the 5 d treatment, and the 0 day treatment will need to be imbibed 24 h before the beginning of the germination test. All treatments will be put in the germinator at the same time.

Report: Show in two figures the relation between days since the start of the germination test and percent germination. Use one figure for each of the temperatures, and plot the three stratification treatments on the same figure. Calculate and show in a table the total germination, the median germination day (day when 50 % of the seeds had germinated) and the duration (number of days between the days when 15 and 85 % germination occurred). The median germination day and duration are calculated based on the number of seed germinated.

1. Describe the effects of stratification and the germination temperature on the total germination, median germination day and the duration of germination.
2. Which stratification treatment gave the most rapid, uniform and complete germination?
3. Which germination temperature gave the most rapid, uniform and complete germination?
4. What is the practical advantage of stratification for a nursery manager, of seed dormancy?
5. State the adaptive advantage for plants of having seeds that are dormant.