Which Chemical is Photosensitive and Allows Plants to "Measure" Day

Question

Which chemical is photosensitive and allows plants to "measure" day length?
A) abscisic acid
B) malic acid
C) cytokinin
D) phytochrome

Accepted Answer

Phytochrome is the photosensitive chemical that allows plants to measure day length through a process called photoperiodism. It helps regulate various plant processes, including flowering, depending on the length of day and night. Abscisic acid, malic acid, and cytokinin play different roles in plant physiology but are not directly involved in measuring day length.