Other Hormonal Signals during Ripening - Fruit Ripening: Physiology, Signalling and Genomics - page 210

12

Other Hormonal Signals during
Ripening

Christopher Davies* and Christine Böttcher
CSIRO Plant Industry, Glen Osmond, SA, Australia

In our minds, the critical criteria
required to make a convincing case for a
hormone's involvement in the control of
ripening are as follows: (i) if the hormone
in question is an inhibitor of ripening, then
its level, or sensitivity to it, should
decrease before ripening initiation; if it is a
promoter of ripening, the levels, or
sensitivity to it, should increase before or
coincide with, the initiation of ripening;
(ii) in most cases, it would be expected that
exogenous hormones, or inhibitors of
hormone synthesis or perception, affect
fruit development in line with their
proposed action. Manipulation of the
hormonal status or response through
transgenesis should also have effects
consistent with the proposed role. During
the following discussions, it will become
clear that, for a number of hormones, not
all of the above criteria will be met.
We have not included a detailed discus-
sion of the voluminous data concerning
treatment of fruits with hormones and
plant growth regulators that may affect
ripening. This is not merely a question of
available space due to the large numbers of
studies (for example, one review of
jasmonate application in horticultural
crops quotes 381 papers; Rohwer and
Erwin, 2008)). Although useful, this data

12.1 Introduction

Ask any plant biologist which hormone is
involved in fruit ripening and the answer
will almost inevitably be 'ethylene'. The
role of ethylene during fruit development
has been much discussed, and the case for
it being pivotal in climacteric ripening is
well established (see Grierson, Chapter 10,
and Kumar and Sharma, Chapter 11, this
volume). This simple molecule has
dominated the research effort into the
control of fruit ripening. This is partly
because of its rather obvious effects on the
ripening of some fruit and partly because it
coordinates the ripening of many
commercially important fruits that can also
serve as model species for study, such as
tomato. However, ethylene is far from
being the only hormonal infl uence on fruit
ripening. There is increasing interest in
other hormones that deserve our attention
with regard to the control of ripening in
both climacteric and non-climacteric fruits.
This chapter will outline the role of other
hormones that may affect fl eshy fruit
ripening. It is not intended to be an
exhaustive review of the literature; rather,
we seek to explore the role of 'non-
ethylene' ripening control with the use of
relevant examples.