Dormancy breaking treatments
If you suspect seeds are not germinating because of dormancy, it is important to find out as much information as you can about the species. Conduct a literature search on its behavior in storage, and climate data for the conditions it grows under in situ. Then consider which dormancy-breaking treatments might be relevant, from the list of treatments below.
Treatments for dormancy:
Scarification: is a process of surgically breaking the seed coat. In some seeds scarification is thought to mimic the way the seed coat decays as a result of diurnal temperature fluctuations or microbial activity. In other seeds, it may mimic digestion by animals or the heat of fire. If your seeds do not come from the families known to exhibit physical dormancy, you do not need to scarify.
Stratification: is a process of altering the temperature to simulate changing seasons. Depending where the seed originates, stratification can mimic the cold of winter, or the heat of a dry season.
Dry after-ripening: is a process of drying, which is thought to destroy hormones that suppress germination.
Chemicals: gibberellic acid (GA3) may tilt the seed’s biochemistry in a direction more favorable to germination by stimulating enzymes that convert starch into sugar.
Dark and light: modifying light conditions may exert dormancy-breaking effects by gradually converting the pigment phytochrome R into phytochrome FR, or altering the activity of hormones and enzymes.
Time: can break morphological dormancy by enabling the seed to develop under suitable ambient conditions for them to mature.
Activity 2
Allow five minutes for this activity.
For each of the treatments above, think about which type of dormancy (i.e.: physical, morphological, physiological) is most likely to respond positively to that treatment. Write your answers in the note-writing box before looking at the authors’ comments.
When you are ready, press 'reveal' to see our comments.
Discussion
You probably made connections between scarification and physical dormancy, time to mature and morphological dormancy, and chemical treatments with physiological dormancy. It’s worth bearing in mind that some treatments can be effective for a variety of different types of dormancy, for instance scarification can be used to overcome both physical and physiological dormancy. Where a species shows more than one type of dormancy, you may need to try different treatments.
Reviewing your progress