1. Discuss the kind of hormone you might find in a rooting compound sold in garden stores, and compare your expectations with what you find on the label of such compounds.
2. Discuss the effects of auxins and cytokinins on the undifferentiated callus of plant tissue in culture, where auxins produce root tissue development and cytokinins produce shoot development.
3. Consider the actions of ethylene, which is produced by a ripening fruit and causes its continued ripening. This is an example of positive feedback, not a reversible reaction.
4. Discuss how the chemical changes of Pr to Pfr
in the presence of red (normal) light and of Pfr to Pr in the
presence of far-red (twilight) light or darkness are associated
with the actions of long-day and short-day flowering plants. Pfr
acts to stimulate flowering in a long-day plant and acts to inhibit
flowering in a short-day plant, which explains the effects of
a short burst of light in the middle of darkness in both kinds
of plants.