The unsaturated fatty acids with more cis- bonds are extremely sensitive to light and will spoil rapidly when exposed to it. The oils quickly become rancid and unfit to eat. When the EFAs and their highly unsaturated cousins are exposed to sunlight, free radical chain reactions begin. A single photon may be caught by an electron on a carbon next to the cis- bonded pair. That excited electron leaves orbit and crashes into another one or takes off with a hydrogen nucleus causing a chain reaction that continues for 30,000 cycles.
Bonds break along the chain.
New and different molecules are formed. Though life cannot flow without the light and oxygen sensitive EFAs, they quickly become toxic when handled incorrectly. Nature solves this paradox by making powerful antioxidants and free radical scavengers that control the oxidation rate and trap free radicals before chain reactions get out of control. Plants have created the perfect container to safely store the EFAs and protect them from light and oxygen damage. It is the seed.