Explanation:This question was inspired by Quyen Nguyen Van of the Vietnam Olympiad.This question ties together the themes of metabolism, studying gene function, and environmental influence.Compare 2 to 3. Increased light exposure does not increase cell death to anywhere near the same extent aschanging the overall day+night length.See aboveWhen the receptor is lost, death/stress increases.Accounts for the very severe inability of receptor knockout plants to cope with changed day+nightlengths.