Answer
Our knowledge of the control systems in plants can be used to modulate their growth as desired-- for example, to inhibit their elongation to produce more dwarf, attractive plants for sale. Any of the control systems can be manipulated to alter plant growth or physiology to make the plants respond better to conditions in the field or greenhouse.
Work Step by Step
The key here is to see that agriculture and horticulture involve getting plants to grow in ways that we want, so we need to manipulate the control systems which we understand to obtain the desired growth results.
