Nature will find its own way to regulate the equilibrium and resistance of its organisms . When we look at the distribution of flora at an area , not even at an area, across the globe they would survive varying climate and circumstances . This survival instinct is regulated through different methodologies . One of such methods is shedding of leaf. This process is known as abscission . Trees would shed leaves inorder to survive extreme temperature like summer , thus reducing the surface area. This process is maintained by a hormone known as abscisic acid. When time approaches the plant or tree would start to secrete abscisic acid and this acid creates senescence and make leaves fall and ripe fruits fall.