Before revision: Some long-day obligate plants are: Carnation (Dianthus) Henbane (Hyoscyamus) Oat (Avena) Some long-day facultative plants are: Pea (Pisum sativum) Barley (Hordeum vulgare) Lettuce (Lactuca sativa) Wheat (Triticum aestivum) Short-day plants Short-day plants flower when the night lengths exceed their critical photoperiod.
After revision: (also called long-night)Some long-day obligate plants are: Carnation (Dianthus) Henbane (Hyoscyamus) Oat (Avena) Some long-day facultative plants are: Pea (Pisum sativum) Barley (Hordeum vulgare) Lettuce (Lactuca sativa) Wheat (Triticum aestivum) Short-day plants Short-day plants flower when the night lengths exceed their critical photoperiod.