Answer: The sequence of events of avocado seed germination includes:
Water absorption --> enzyme activation --> radicle emerges --> lengthening of the hypocotyl --> growth of epicotyl and plumule development --> shrinking of the cotyledons.
Explanation:
Germination is defined as all the changes that occurs when a seed embryo resumes it's growth and development to become an independent seedling. Seeds usually germinate in two ways:
--> EPIGEAL germination: in this type of germination, the hypocotyl grows rapidly and elongates, carrying the cotyledon above the soil.The AVOCADO seed is a typical example of a dicotyledonous plant.
The sequence of events of avocado seed germination starts by imbibition which is the rapid in take or absorption of water by the seed through osmosis. Hydration of the embryo activates the enzymes in it which converts insoluble stored food materials into soluble forms. The testa splits and the radicle emerges first. It grows downwards as the primary root from which root hairs and branch roots arise( to form a tap root system). Next, the hypocotyl lengthens, pushes its way up through the soil carrying with it the cotyledons and the plumule. The cotyledons turn green on exposure to sunlight and start to photosynthesize. The epicotyl then grows and the plumule develops into a green shoot. By the time the first foliage leaves grow and begin to photosynthesize, the cotyledons shrink and drop off.