The percentage of germination of lettuce seeds exposed to far-red light, then blue light, and then red light compared to lettuce seeds that were exposed to far-red light only would be expected to be .

50%

Explanation:

Since it was not a case of a Lettuce seed exposed first to red light and then to far-red light which will very likely not germinate because Pr (chromoprotein inactive form) absorbs red light efficiently, the light absorbed will convert a high proportion of the molecules to the Pfr (chromoprotein active form), thereby inducing germination. So there is a 50/50 percentage chance of of germination.

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