十万个为什么·科学阅读30篇（1）

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风滚草如何在干旱土地上传播种子？

Tumbleweeds are whole plants that break free from their roots when dry and roll with the wind.
Their round, spiny shape helps them bounce over rough terrain without getting stuck easily.
As they tumble, thousands of tiny seeds shake loose from special compartments inside the dried branches.
These seeds have tough outer coats that let them survive long journeys across deserts and plains.
Wind speed, terrain slope, and rainfall patterns all influence how far a tumbleweed travels before stopping.
Once it lands in moist soil, the plant’s remaining seeds may germinate when spring rains arrive.
Some tumbleweeds spread invasive species, while others help native grasslands recover after fire.
Unlike most plants, tumbleweeds don’t rely on animals or water—they use pure physics to disperse life.
Botanists study their movement to improve models of seed dispersal in arid ecosystems.
This clever survival strategy shows how evolution shapes motion into a tool for reproduction.