Plant growth hormones and insect metamorphosis
BiologyPlant PhysiologyAges 16–17
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Plant Physiology
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. In applications mode, set the dose of a selective weedkiller, a rooting powder, ethene in a ripening room, gibberellin on dormant seeds or grapes, ethene on dark-grown seedlings or ABA on leaves, and read the outcome on the dose-response curves.
Lesson: Plant hormones and hormonal control of metamorphosis in animals
What it shows
Plant hormones act at tiny concentrations, and their effect depends on the dose and the tissue. Auxin stretches stem cells at moderate concentrations but inhibits them at high ones, and roots respond to concentrations about ten thousand times lower, so one dose can stimulate the stem and inhibit the root. In phototropism auxin moves to the shaded side and the shoot bends toward light. Growers use these effects: synthetic auxins kill broad-leaved weeds and root cuttings, ethene ripens fruit, gibberellin breaks seed dormancy and enlarges grapes, and ABA closes stomata. In insects, ecdysone triggers each molt while juvenile hormone keeps the larval form.
How to use
On Plant – growth hormones, choose the Hormone and drag the Concentration, watching stem, root and the dose-response curve; turn on One-sided lighting to see the stem bend. On Insect – complete metamorphosis, follow the butterfly with its hormone graphs. On Applications, choose a Hormone use, set the dose and let the treatment run; each finished run adds a row to the table.
Parameters you can change
- Organism Plant – growth hormones, Insect – complete metamorphosis, Applications – hormones in farming
- Hormone applied to the plant Auxin (IAA), Gibberellin (GA), Cytokinin
- Hormone concentration (log[M], −10 = very dilute) -10–-3 log M
- One-sided lighting
- Simulation speed 0.3–3 days/second
- Hormone use Selective weedkiller (2,4-D), Rooting cuttings (IBA), Ripening fruit (ethene), Breaking seed dormancy (GA₃), Larger grapes (GA₃), Triple response (ethene), Closing stomata (ABA)
- Dose (log₁₀ of the concentration in M, or in ppm for ethene) -9–3 log
- Dry soil (the plant makes its own ABA)
- Seeds also soaked in ABA
Questions to explore
- At which auxin concentrations is the stem stimulated while the root is inhibited?
- Why does a stem lit from one side bend toward the light?
- What change in juvenile hormone lets a larva pupate instead of molting into a larger larva?
- Why does a 2,4-D spray kill broad-leaved weeds in a lawn but leave the grass alive?
