十万个为什么·科学阅读30篇（4）

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为什么一些仙人掌只在夜间开花，并在日落后释放浓烈香气？

Nocturnal cacti like the night-blooming cereus open their large white flowers after dusk.
They rely on moths and bats—not bees or birds—for pollination during darkness.
Strong floral scent attracts these pollinators from hundreds of meters away in desert air.
The fragrance chemicals include benzenoids and terpenes that evaporate best in cooler, humid night air.
Flowers close before sunrise to conserve water and avoid daytime heat stress.
Their petals reflect moonlight efficiently thanks to microscopic surface structures.
Some species bloom just once per year, often synchronized by lunar cycles and rainfall.
Scientists track flowering timing to assess climate change impacts on desert ecosystems.
Genetic studies show rapid evolution of scent genes in response to local pollinator decline.
This precise timing proves plant behavior is shaped by co-evolution—not mere chance.