Effects of Low Temperature and Age of Plant on Flowering in Lolium perenne L. 1

"EXPOSURE to winter conditions of low temperatures -*-' and short days greatly hastens the emergence of the inflorescence of many temperate grasses when they are subsequently exposed to long days and warm temperatures. Species and strains vary from those with no cold or shortday requirement for flowering to those in which such are obligatory. Between these extremes, the flowering response is proportional to length of exposure to these pre-induction conditions. Research on "seed chilling" has been conducted for more than a century, but the importance ,of the shortday component of winter conditions has been realized only in recent years. Although efforts to elucidate the mechanisms of vernalization have not been very rewarding, charting the effects of various pre-induction treatments has enabled the plant scientist to control life cycles of many species (2). The authors encountered difficulties in obtaining expected results by chilling germinated seeds in preliminary experiments with those strains of perennial ryegrass known to have high pre-induction cold requirements as mature plants. The present experiments were conducted to determine if the stage of seedling development or age of plant