Admired worldwide for their beauty, flowers are actually the reproductive parts of the plant. Like any other part of the plant, flowers are affected in a negative way by the lack of sunlight for longer periods of time. By not receiving light, plants are not able to make energy and will die.
The light deficiency is one of the major causes that lead to the death of a plant. Flowers without sunlight cannot develop and the existing ones will fade away and shrivel while becoming brown or black. Before their flowers start shriveling, some species of plants can last longer without sunlight, other less. For example, larger plants can tolerate shade for longer, as they store more energy when the sun is out. Large plants can survive for months without sunlight, while the smaller ones last only for a few days without the benefits of the sunlight before their flowers start withering. Still, there are plants, such as the resurrection plant (a species of Selaginella), that can resists for a couple of years without sunlight because they significantly lower their metabolic processes.
Actually, flowers do not require light for themselves, is the plant that needs light in order to produce energy and send it to its flowers. The process is the following: plants transform sunlight into usable sugars and transmit it to all its parts, including flowers, sustaining this way all its functioning. If there is not sunlight received, there is no energy to give to the flowers and the rest of the plant, leading to death of the entire plant. On the other hand, too much sunlight can also destroy flowers and plants, it depends on the species and their light requirements and tolerance.
There are flowers that can live without sunlight. These are the nocturnal flowers that bloom only by night. Anyway, the plant itself cannot survive without sunlight, as its flowers use the energy captured during daytime.