The key difference between stratification and scarification is that stratification is the mechanism in which seeds experience a period of moist and cold conditions to induce germination. Meanwhile, scarification is the mechanism in which seed germination is induced by breaking the seed coat.
Seeds develop into plants via a process called seed germination. To germinate, seeds require certain conditions such as temperature, water, oxygen or air and sometimes light or darkness. Until the conditions are favourable, seeds remain in dormancy. Stratification and scarification are two types of mechanisms that induce seed germination by breaking the seed dormancy. In stratification, seeds are put in moist cold conditions in order to stimulate seed germination and break internal dormancy. In scarification, the seed coat is broken down by scratching or removing in order to overcome physical dormancy.
CONTENTS
1. Overview and Key Difference
2. What is Stratification
3. What is Scarification
4. Similarities Between Stratification and Scarification
5. Side by Side Comparison – Stratification and Scarification in Tabular Form
6. Summary
What is Stratification?
Stratification is a mechanism that helps to overcome physiological dormancy of seeds. In other words, stratification helps to break embryonic or internal dormancy of seeds. Hence, stratification refers to the mechanism in which seeds are put under moist and cold conditions for a period of time in order to stimulate seed germination. Here, the temperature plays a major role in breaking dormancy of seeds. In this method, seeds are stored in a temperature of 2°-4 °C (36°-40°F) for 6-8 weeks. Therefore, the cold, moist treatment encourages the seed’s embryo to grow and eventually break through the softened seed coat. Some seeds are kept underground in winter.
Figure 01: Stratified Seeds
However, some seeds prefer warm stratification. In warm stratification, seeds are put under a temperature of 15-20 °C (59-68 °F) up until germination takes place.
What is Scarification?
Seeds start to germinate by absorbing water from the soil through their seed coats. We call this process imbibition. Some seeds have very thick and hard protective seed coats which are impermeable to water. Therefore, the seeds do not germinate due to physical dormancy. In order to induce seed germination, the seed coat can be removed or scratched.
Figure 02: Scarification
The removal or scratching of the seed coat to induce seed germination is known as scarification. This can be achieved in several ways. The seed coat can be scratched using sandpaper. Also, one end of the seed coat can be cut. A crack can also be created in the seed. Besides, seeds can be soaked in sulfuric acid (chemical scarification).
What are the Similarities Between Stratification and Scarification?
- Stratification and scarification are two types of mechanisms that help to overcome seed dormancy.
- Both methods stimulate seed germination.
- The timing of both methods is critical to ensure that the environment is favourable for both the emergence and survival of the seedlings.
What is the Difference Between Stratification and Scarification?
Stratification is the mechanism of putting seeds under moist cold conditions for a specific period of time in order to overcome internal dormancy while scarification is the mechanism of scratching or removing seed coat in order to overcome physical dormancy. So, this is the key difference between stratification and scarification. Moreover, in cold stratification, the seeds are kept under a temperature of 2°-4 °C (36°-40°F) for 6-8 weeks, while in warm stratification, seeds are put under a temperature of 15-20 °C (59-68 °F) up until germination. In scarification, seed coat can be scratched using coarse sandpaper, cut from one end using a knife, soak in sulfuric acid and make a crack on the seed. In brief, stratification focuses on the change of temperature while scarification focuses on the breakdown of the hard impermeable seed coat.
By stratification, physiological dormancy can be overcome while by scarification, physical dormancy can be overcome. Furthermore, stratification can be cold and warm while scarification can be mechanical, chemical and thermal.
Below infographic summarizes the difference between stratification and scarification.
Summary – Stratification vs Scarification
Stratification and scarification are two techniques that induce seed germination. Stratification uses temperature to break dormancy, while scarification breaks down the seed coat, which is hard and impermeable to water. In stratification, seeds are mostly put under moist and cold conditions to stimulate germination. In scarification, scratching or removal of the seed coat is done. Thus, this summarizes the difference between stratification and scarification.
Reference:
1. “Scarification and Stratification.” The Gardener’s Alamanac, Available here.
2. “Seed Treatments: Soaking, Scarification and Stratification: The Seed Collection.” TheSeedCollection, Available here.
Image Courtesy:
1. “2007. Stratified whitebark pine seeds ready for scarification. Dorena Genetic Resource Center. Cottage Grove, Oregon.” By R6, State & Private Forest (Public Domain) via Flickr
2. “Mechanical scarification of Acacia seeds” Аутор: Gmihail at српски Википедија – Сопствено дело (CC BY-SA 3.0 rs) via Commons Wikimedia