Plant growth hormones and insect metamorphosis

BiologyPlant PhysiologyAges 16–17

In plant mode, treat a seedling with a hormone at a concentration you drag along the scale: at low concentrations auxin stretches the stem but at high concentrations it inhibits growth, while the root tolerates only very low concentrations; gibberellin elongates internodes, turning a dwarf plant tall; cytokinin promotes lateral bud growth. Switch on one-sided lighting to see auxin build up on the shaded side, bending the stem toward the light, and read the dose-response curve for both stem and root. In insect mode, watch the complete metamorphosis of a butterfly animate alongside graphs of ecdysone and juvenile hormone, which together decide molting or pupation.