Inflorescence Initiation in Lolium Temulentum l. I. Effect of Plant Age and Leaf Area on Sensitivity to Photoperiodic Induction

As they increase in age, plants of L. temulentum require exposure to pro· gressively fewer long days before they can initiate inflorescences, until, after being grown for 5 weeks at 25°C for 8 hr and at 20°C for the remainder of each day, they require only one long day. This increase in sensitivity to photoperiodic induction with age varies to a slight degree with seasonal light conditions. In young plants, exposure to long days for less than the period required for inflorescence initiation increases the rates of leaf initiation and apex elongation.