Effects of photoperiod in growth cabinets on the growth of leaves and tillers in three perennial grasses

SUMMARY Long photoperiods provided in growth cabinets and consisting of a conventional extended photoperiod or of a ‘light‐break’ in the middle of a long, dark period, generally increased leaf length and sometimes leaf width and consequently the rate of expansion of leaf surface, but decreased rate of leaf production and tillering in vegetative plants of S. 37 cocksfoot ( Dactylis glomerata L.), S. 215 meadow fescue ( Festuca pratensis Huds.) and S. 24 perennial rye‐grass ( Lolium perenne L.) compared with short photoperiods. All plants received the same total amount of light each day. These effects were observed both in single plants and in plants grown close together to simulate sward conditions. The total dry weight of plant material was greater in long than in short photoperiods.