Complex sentence: Plants which exhibit photoperiodism may be either'short day' or'long day' plants, which in order to flower require short days or long days respectively, although plants in fact distinguish day length from night length.
Split into simpler sentences: Plants which exhibit photoperiodism may be either'short day' or'long day' plants, which in order to flower require short days or long days respectively. Although plants in fact distinguish day length from night length.