Effect of red and far-red irradiation on ABA and IAA content in Pinus sylvestris L. seed during the escape time period from photocontrol

The time-course of ABA and IAA dynamics in the photosensitive Scots pine (Pinus silvestris L.) seed was followed during the escape time period from photocontrol, with recordings of the respective hormone immediately before and after a 15-min red irradiation (R) stimulus and after subsequent dark incubation for periods of 10 min, 30 min, 4 h, 8 h and 24 h. The control treatment was exposure to R as above immediately followed by exposure to 5-min far-red irradiation (FR), and its effect was recorded in parallel. The hormones were identified on a gas chromatograph with a mass selective detector, and quantified on a high performance liquid chromatograph with UV detector and spectrofluorophotometer, respectively. Only ABA responded differently to the two irradiation treatments. The difference in ABA content between paired treatments with R and R + FR was significant after 6 to 8 with an enhanced decrease in ABA content in seeds that received a dormancy-breaking R treatment. The IAA content in the seeds decreased during the experimental period regardless of the type of irradiation treatment.