Plant Hormones

Auxins

• Growth promoter
• Production site: Apical meristem (shoot)
• cell elongation, development of vascular tissue, above-ground stems, growth of lateral branches
• Commercial use: stimulating rooting, prevent fruit from dropping too soon

Gibberellins

• Growth promoter
• Production site: Apical meristem
• accelerated growth (tall), increase stem length, increase starch uptake in germinating seed embryo, stimulates development of vascular tissue, stimulates vascular tissue to produce secondary phloem
• Commercial use: taller, stronger plants, easy flowering, dwarfs grow to normal height, increase fruit and grape cluster size, delay the ripening of citrus

Cytokinins

• Growth promoter
• Production site: mainly roots, minor stems & leaves
• promote cell division & differentiation, delay aging of leaves and fruits, stimulate formation of adventitious buds
• Commercial use: reverse auxin suppression, increase fruit size, prevent salad browning

Oligosaccharides

• Growth promoter
• Production site: cell walls
• stimulates antibiotic manufacture; complex carbohydrate molecular signals for the plant

Absibis Acid (ABA)

• Growth inhibitor
• Production site: chloroplasts and other plastids
• inhibits seed germination and growth of buds in stems, blocks CO2 by controlling the opening and closing of stomata in leaf, blocks growth promoting hormones, promotes abscision of leaves and fruits

Ethelene (Ethene)

• Growth inhibitor
• Production site: gaseous hydrocarbons produced by fruits
• stimulates aging of plant tissue, ripening of fruits and sweetening; speeds up dropping of tree leaves
• Commercial use: agriculture (banana ripening), pick tomatoes green then ripen