Final answer:
The type of seed dormancy that is broken by sixty to ninety days at temperatures of 40 to 45 degrees is called cold stratification. Certain plant species require this cold treatment in order to germinate.
Step-by-step explanation:
The type of seed dormancy that is broken by sixty to ninety days at temperatures of 40 to 45 degrees is called cold stratification.
Cold stratification is a process in which seeds are exposed to a period of cold temperatures to break their dormancy and promote germination. Certain plant species require this cold treatment in order to germinate, as it mimics the natural conditions they would experience in their native habitats.
During cold stratification, the accumulation of 'chill units' occurs, which are measured in terms of the number of hours or days that seeds are exposed to temperatures below a certain threshold. Once a seed has accumulated enough chill units, its dormancy is broken and it is able to germinate when conditions become favorable.