Summary Phytohormones are chemical messengers that coordinate cellular activities. This lecture introduces the plant hormones (auxin, cytokinin, gibberellic acid, brassinosteroids, ethylene, abscisic acid, salicylic acid and jasmonic acid) through their roles, during the plants life, from seed-to-seed. The biosynthesis, transport, perception, signal transduction and downstream effects of each are introduced, as well as a few ways that hormonal signaling pathways intersect.