alkene biosynthesis ethylene biosynthesis Biosynthesis of ethylene, an unsaturated hydrocarbon that contains one double bond (the simplest alkene). It acts as hormon in plant where it is essential for proper development, growth and survival. It is responsible for signaling changes during germination, flower and fruit development, the onset of plant defense responses, and cross-talk with other plant hormones. UPa:UPA00368 GO:0009693 pathway