Kinetics of Growth: Stages in Growth Rate

Kinetics of growth is the study of how fast growth proceeds, tracked across an organ's entire 'grand period of growth' - from its very first growth to the point growth stops. Plotting total size or weight against time over this whole period does not give a straight line; it gives a characteristic S-shaped, or sigmoid, curve, and this curve breaks down into four recognisable stages, shown in Figure 15.2. The lag phase is the slow opening stage, where new cells are being formed from pre-existing ones only gradually - it is where growth genuinely begins. The log (or exponential) phase follows, where cell division and the underlying physiological machinery run at their fastest, driving the fastest growth of the whole curve and notably stretching out the stem's internodes. The decelerating (or decline) phase comes next, where internal and/or external limits slow the metabolic processes down and the growth rate visibly falls. Finally the …