Photoperiod and photosynthetic capacity in Lotus scoparius

Leaves of Lotus scoparius Nutt., a Mediterranean‐climate shrub, exhibited higher photosynthetic capacities when grown under winter (10/14 h, day/night) than summer (14/10 h) photo‐periods, even though total daily photon irradiance was higher under summer photoperiods. Photosynthetic dependence on natural variations in photo‐period, such that activity was higher under photo‐periods associated with expected precipitation, may be a more dependable environmental parameter than total irradiance in temperate habitats with winter‐spring precipitation patterns and where seasonal cloudiness may cause total daily irradiance levels to be highly variable.