The phenomenon by which the detachment of leaves from the parent plant takes place is known as abscission. It is necessary for plants for the removal of excretory products. In this process, the formation of a distinct zone called abscission zone or separation zone occurs at specific sites in plants (e.g. base of the petiole in leaves) that causes the detachment of leaves, flowers and fruits from the mother plant. Hormones that influences abscission are auxin, ethylene, and abscisic acid. Abscission can be delayed by the application of auxins.

A growth curve is a graphical representation showing the way a particular quantity increases over time. We can obtain a sigmoid growth curve in plants if we plot the increase in cell number (growth rate) against time. There are three phases of a logistic growth curve: lag phase, log phase, and stationary phase. The second phase is called the log phase or exponential phase that shows the maximum growth rate. In the log phase, the cell elongation and growth rate becomes maximum. Thus, during the log phase, exponential growth is noted, and the line goes upward in the graph. This phase is regulated by different enzymes and hormones.