What is the mechanism by which seeds stay alive while in storage?
Seeds are made from cells in an amorphous metastable superviscous state because the cell's cytoplasm becomes a solid matrix of hydrogenated oil and sugar. The fats also contain a lot of anti-oxidants, so that ambient oxygen that can affect the dormant cells is absorbed by buffer chemicals.
The sugars and oils in the cell cytoplasm (the inside of the cell) become hydrogenated, and change into margarine and then become solidified fat and solidified sugar. Then the consistency of the cell at that stage becomes glassy because it's so solid, which is what you can see if you try to crack a peanut or a lentil, it has a glassy surface. The cell fats can rapidly become liquid again if they absorb water and change their chemistry.
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It's not very different from microbe dormancy, so it's like an ancient biological trick that cells have been doing for billions of years.
The cotyledon is the future baby leaves of the seedling, the radicle is the root and the plumule is the leaf shoots, they are all made of cells that are in a solidified dehydrated form made of fats and sugars and special chemicals that resist ambient water and oxygenation in a controlled way.