Photoperiodism refers to the response of plants to the duration of light and darkness in a 24-hour period. It plays a crucial role in regulating various plant processes. The correct answer, option 1, "All of these," indicates that photoperiodism affects all of the mentioned processes: flowering, vegetative growth, and fruiting.

Flowering is greatly influenced by the duration of light exposure and determines the timing of the plant`s reproductive stage. Vegetative growth refers to the development of leaves, stems, and branches, and photoperiodism affects the rate and pattern of growth. Fruiting, the development of fruits and seeds, is also regulated by photoperiodism.

Therefore, option 1 is accurate, indicating that all of these processes are affected by photoperiodism. It is important for plants to respond to changes in light duration to optimize their growth, reproduction, and survival.