You are growing a Chrysanthemum plant in an artificial growth chamber in a florist shop. You want to induce the plant to flower, so since this is a "fall" plant, you grow it in 1. . By accident, a night-watchman checking the facility turns a flash-light on in the growth chamber in the middle of the night. This short pulse of white light activates 2. , which interrupts the 3. that controls flowering, and thus the plant 4. .

You are growing a Chrysanthemum plant in an artificial growth chamber in a florist shop. You want to induce the plant to flower, so since this is a "fall" plant, you grow it in 1. long day/shortnight. By accident, a night-watchman checking the facility turns a flash-light on in the growth chamber in the middle of the night. This short pulse of white light activates 2. phytochrome, which interrupts the 3. criticaldark period that controls flowering, and thus the plant 4. flower.

Explanation:

Integumentary and respiratory is the answer