Plant Hormones – S6 Biology Notes

These Senior 6 Biology notes cover plant growth regulators under the coordination topic. They start with the general features of plant hormones, then take each of the five main groups in turn: auxins, gibberellins, cytokinins, ethene and abscisic acid. For each group the notes explain its effects, such as cell elongation, apical dominance, tropisms, breaking dormancy, fruit ripening and abscission. They also show how auxin concentration affects growth differently in roots and shoots, explain how hormones work by switching genes on and off, and list commercial uses including selective herbicides, rooting powders and controlled fruit ripening. The notes end with structured exam-style exercise questions that carry marks.