Although d is a correct answer in that day length changes the amount of energy available to a plant, and flowering can be influenced by the energy status of the plant, it is NOT what directly affects phytochrome. I spent 5-10 minutes on this in a lecture. Under the first set of conditions, the plants flowered, but they failed to flower under the second set of conditions. Zero, one, two, three, or four of answers may be correct. 0-4 points possible for each question. You are studying a plant from the arid southwestern United States.
Day length has a small influence.
This is a figure of caged and uncaged saguaro cacti transplanted in Saguaro National Monument, Arizona. This is a figure of two pinyon pines, one shows the affects of accumulated herbivore attack by a stem and cone boring moth. This photograph illustrated three general effects herbivores can have on plants at the whole-plant level. You carve the name of a sweetheart in the trunk of a tree that is 3 meters tall. The name is carved 1.5 meters from the ground.