The researchers studied how changes in hormones affect bud development in chestnut trees. They found that IAA levels increased during bud differentiation, while ABA levels first rose, then fell, and rose again. GA3 levels initially increased, then decreased, and remained low. ZR levels increased, then slowed down. High ZR/IAA, GA3/IAA, and ABA/IAA ratios helped chestnut shoots break dormancy, but lower ratios were needed for flower cluster development. The balance of hormones in chestnut buds is crucial for different stages of growth.