1. Plant Hormones Auxin Promotes plant growth
Causes elongation of developing cells
Increases the concentration of H+ in primary cell walls, in turns, loosens cellulose fibers which increase cell wall plasticity.
In response, turgor pressure causes the cell wall to expand, thus generating growth.
Produced at the tips of shoots and roots
Active in phototropism and geotropism
Active in leaves, friuts, and germinating seeds

2. Plant Hormones Gibberellins (gibberelic acid- GA) Promotes cell growth
Synthesized in young leaves, roots, and seeds
Involved in the promotion of fruit development and seed germination
High concentrations of GA causes rapid elongation of stems called bolting

3. Plant Hormones Cytokinins
Group of hormones that stimulate cytokinesis (cell division)
Produce mainly in the roots and transported throughout the plant
Stimulates the growth of lateral buds, thus weakening apical dominance

4. Plant Hormones Ethylene Gas- C2H4 Promotes the ripening of fruit
Involved in stimulating the production of flowers
In combination with auxin, ethylene inhibits the elongation of roots, stems, and leaves, and influences leaf abscission, the aging and dropping of leaves.

5. Plant Hormones Abscisic acid (ABA) Growth inhibiter
Maintains dormancy in seeds, in many species of plants.