Final answer:
The experiment indicates that the observed woody plant species is likely a short-day plant, requiring more than 9 hours of darkness to initiate flowering, which is significant for the agricultural control of blooming.
Step-by-step explanation:
The experiment conducted by the florist in the Northern Hemisphere on shrubs of the same woody plant species under different light schedules yields an interesting conclusion about the photosensitivity of the plants. The set of plants that received 15 hours of light did not form flowers, while the set with only 9 hours of light followed by 14 hours of darkness did bloom. This suggests that the plant species in question requires a longer period of darkness to initiate flowering, a characteristic known as being a "short-day plant". Short-day plants typically flower when the night is longer than a critical length, in this case more than 9 hours. It seems for this plant species, the critical night length is likely between 9 to 14 hours. Hence, knowing the critical night length is essential for controlling the flowering time of these plants, which can be particularly important for commercial purposes in horticulture and agriculture.