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How can some seeds survive extreme heat or brief boiling?

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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.

Many dry seeds possess a remarkable resistance to extreme temperatures, allowing them to survive conditions that would otherwise be lethal to active plant tissues. This resilience is largely attributed to the physical properties of the seed coat, or testa, which protects the dormant embryo from environmental stressors.12

In many species, such as Scotch broom and certain Medicago plants, the seed coat is sufficiently robust to withstand brief exposure to boiling water without losing viability. This heat resistance is an important ecological adaptation for plants in fire-prone habitats, such as the California chaparral. For some species, heat is not merely something to be endured but a requirement for germination; the heat of a fire can physically melt resinous seals on cones or fruits, or trigger chemical signals from smoke that break seed dormancy.13

In agricultural and horticultural practices, humans mimic these natural processes through scarification, which involves deliberately damaging or weakening the seed coat using methods like boiling water or strong acids to facilitate water uptake and germination.4