Effect of Gibberellin on Mature Euonymus europaeus L. Seeds

The release from dormancy of Euonvmus europaeus L embryos bya brief treatment with GA₃ has been studied During 48 h incubationof dormant embryos in GA-free medium, phospholipid levels increasedat first, then declined sharply over the last 6 h When the embryoswere placed in GA₃ medium during this 6 h period levels of totalphospholipids as well as of phosphatidylethanolamine increasedwhilst phosphatidylinositol and phosphatidylcholine declinedslightly Fine structural changes stimulated by a brief GA₃ treatmentwere of different character depending on tissue region (1) ‘destructive’changes occurred in the superficial procortical parenchyma onthe hypocotyl/radicle boundary, involving autolysis and decompartmentationof organelles, (2) ‘positive’ changes occurred inregions close to root and shoot apical meristems, involvingdegradation of protein bodies and their conversion into vacuoles,and the proliferation of various organelles A number of differenceswere noted when the changes in GA₃-treated embryos were comparedwith those induced by low temperature, which also overcomesdormancy The results suggest that germination is accompaniedby different cytological events depending on whether it is inducedby cold or GA₃ The growth of embryos in which dormancy was overcomeby GA3 was due to the activation of the apical root meristemclose to the quiescent centre, whilst in embryos in which germinationwas induced by low temperature, the periphery of hypotocotyl/radicleboundary was the site of activation Euonymus europaeus L, dormant embryo, fine structure, phospholipids, GA₃ and cold treatments