Horticulture Principles and Practices

Growth in an organism follows a certain general pattern described by a sigmoid
curve (Figure 5–1). The pattern and corresponding developmental stages as they occur
in plants are as follows:
1. Lag growth phase. The lag phase includes activities in preparation for growth.
Dormant cells become active; dry tissue imbibes moisture; cells divide and
increase in size; the embryo differentiates.
2. Logarithmic growth phase. The logarithmic growth phase is characterized by an
increasing growth rate and includes seed germination and vegetative plant growth
periods.
3. Decreasing growth phase. During the decreasing growth phase, growth slows
down. This stage includes flowering, fruiting, and seed filling.
4. Steady growth phase. Growth rate either declines or stops during the steady growth
phase. This phase is associated with age, or the plant’s maturity.
The characteristics of the sigmoid growth pattern vary among species and plant
parts. In fruit growth, food materials are translocated from one part of the plant to another.
In species such as apple, orange, pear, tomato, and strawberry, fruit growth follows
the simple sigmoid growth curve, with variations in characteristics. However, in certain
species, including stone fruits, such as plum, peach, and cherry, fruit growth follows a
double sigmoid curve pattern whereby the single pattern is repeated (Figure 5–2). During
the plateau of the first sigmoid curve, the fruit size barely changes; most of the
activities involve seed development. In stone fruits, the hardening of the endocarp (pit)
occurs during the second phase of fruit development.
1
FIGURE 5–1 A typical sigmoid
growth curve. (a) lag phase,
(b) log phase, (c) decreasing
phase, (d) steady phase.
0.5
A B
C D
4
2 0 2 4
Increasing fruit size
Orange
Cherry
FIGURE 5–2 The sigmoid
and double sigmoid growth
curves. Stone fruits are characterized
by the double sigmoid
curve growth pattern. The characteristics
of either curve differ
from one species to another.
Time
5.1 Growth and Development 155