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How can abrasion in soil or an animal’s digestive tract break seed dormancy?

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Cluster of bright red seeds emerging from the cone-shaped fruit of a magnolia grandiflora, surrounded by large, glossy green leaves. — Seed Fruit and seeds of the southern magnolia (*Magnolia grandiflora*). The fruit is an aggregate of follicles, and each follicle bears a single red seed.

Seed dormancy is often caused by a hard, impermeable testa (seed coat) that prevents the embryo from expanding, blocks water uptake, or impedes gas exchange. Abrasion helps break this dormancy by damaging or weakening the seed coat, thereby rendering it permeable to water and gases, which allows germination to proceed.123

In nature, this process occurs through several mechanisms:

Soil Abrasion: Seeds in the soil may be worn down by mechanical friction against abrasive particles like sand or through the natural decomposition caused by microbial attack.13
Animal Digestive Tracts: As seeds pass through the digestive system of an animal, the physical and chemical environment can abrade or weaken the tough seed coat, facilitating future water entry.13

In horticulture and agriculture, humans mimic these natural processes through scarification. This involves artificially damaging the seed coat using mechanical methods—such as shaking seeds with abrasive materials or scratching them—or chemical treatments to ensure uniform germination.12