Pigments in the leaves are primarily carotenoids and chlorophylls. Carotenoids are red, orange and yellow pigments that aren't very good at capturing light energy for other uses. This is common in some genera if light is insufficient. Once the light energy is absorbed by the chlorophyll, it is used to power the formation of sugar molecules from water and carbon dioxide. These sugars are used for structure and energy for growth of leaves, roots and flowers.
Photosynthesis is the term used to describe the energy capture and transfer process.
Even at 10000 footcandles of intensity, green light would not be useful, because chlorophyll reflects it. Growers knows that each species or hybrid, or even each plant, is an individual. Every flowering plant has some mechanism which controls when, and how extravagantly, it flowers. Some plants are said to be sensitive to day length. The plant would respond as if it had experienced several short nights, not a broken long night, and it would bloom.