Climacteric and Non-climacteric Ripening - Fruit Ripening: Physiology, Signalling and Genomics - page 2

In this chapter, we describe the dif-
ferences and similarities among climacteric
and non-climacteric fruits with respect to
the different types of fruit maturation.

duction of system II ethylene is promoted
by ethylene in an autocatalytic manner.
Whether a transition from system I to
system II ethylene biosynthesis is observed
during the initiation of fruit ripening is one
of the differences between climacteric and
non-climacteric fruits (McMurchie et al. ,
1972; Alexander and Grierson, 2002).
Typical climacteric fruits include apple,
avocado, banana, pear, peach, melon and
tomato, and typical non-climacteric fruits
include strawberry, grape and citrus.

1.2 The Concept of Categories in
Climacteric and Non-climacteric Fruit
Ripening

Fruits generally display various bio-
chemical and physiological modifi cations,
including the loss of chlorophyll, the
synthesis of pigments such as antho-
cyanins and carotenoids, increased aroma
and fl avour, alterations in the sugar and
acid components, and softening, in
association with fruit maturation. These
phenomena vary signifi cantly, depending
on the ripening of different fruits.
Classically, the types of fruit ripening are
categorized into two groups: climacteric
and non-climacteric. The classifi cation of
fruits depends on whether ripening-
associated increased respiration occurs in
the fruit (McMurchie et al. , 1972) (Fig. 1.1).
Climacteric fruits are characterized by an
increase in respiration with a concomitant
and rapid production of ethylene at the
initiation of ripening; the produced
ethylene, which is a plant hormone,
accelerates the ripening process (Leliévre
et al. , 1997). In contrast, these changes do
not occur in non-climacteric fruits, and
maturation proceeds relatively slowly.
McMurchie et al. (1972) used the terms
'system I' and 'system II' to describe the
differences in the ethylene biosynthesis
pattern. Fruits continuously synthesize
ethylene at a low level throughout develop-
ment, even during the immature stage. The
production of basal ethylene levels is
called system I synthesis and occurs in
both climacteric and non-climacteric fruits.
The increased production of ethylene at
the initiation of ripening is called system II
synthesis and is observed only in
climacteric fruits. System I ethylene pro-
duction is inhibited by exogenous ethylene
in an autoinhibitory manner; system I
ethylene also functions when the plant
responds to stress. In contrast, the pro-

1.3 Characterization of Climacteric
Fruit Ripening

The term 'climacteric' rise was fi rst used by
Kidd and West (1930) to describe the rapid
increase in respiration that was observed at
the end of maturation in apples, and
'climacteric' was originally defi ned as an
augmentation of respiration. However, the
defi nition of climacteric has changed over
time and now usually refers not only to an
increase in respiration but also to the rapid
increase in ethylene production at the
onset of fruit ripening. To date, the role of
ethylene in the ripening mechanism has
been studied extensively in climacteric
fruits (Leliévre et al. , 1997; Alexander and
Grierson, 2002; Barry and Giovannoni,
2007; Lin et al. , 2009).

1.3.1 Ethylene and climacteric fruit ripening

In climacteric fruits, the plant hormone
ethylene plays an important role in the
fruit-ripening process. Generally, a burst of
ethylene production acts as an initiator of
ripening and triggers the autocatalytic
ethylene production process, thereby
resulting in dramatic changes in colour,
texture, aroma, fl avour and other bio-
chemical and physiological attributes of
the fruit (Fig. 1.1). Moreover, ethylene
production by the autocatalytic processes
accelerates the ripening phenomena.
Therefore, the shelf-life of climacteric
fruits is shorter than that of non-
climacteric fruits. A typical example is