十万个为什么·科学阅读30篇（2）

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为什么有些树只在春天落叶，而不是秋天？

Most deciduous trees lose leaves in autumn to conserve water during cold winters.
But certain species like the Indian coral tree drop old leaves only in early spring.
This timing helps them avoid drought stress while preparing for new growth simultaneously.
Their leaf-shedding is triggered by rising temperatures and longer daylight hours, not cold.
Scientists found that specialized hormones respond to photoperiod cues more strongly than temperature here.
The process allows rapid flowering before new leaves block sunlight from blossoms.
Roots remain active year-round, storing energy for synchronized leaf and flower emergence.
Unlike temperate trees, these species evolved in tropical climates with distinct wet-dry cycles.
Botanists use this trait to study how climate change affects seasonal plant behavior.
Researchers monitor leaf-fall patterns across decades to track ecosystem adaptation rates.