Plant Resistance to Insects by Paul A. Hedin

Bibliographic Information:
Title: Plant Resistance to Insects
Editor: Paul A. Hedin
Edition: 1st
Publisher: ACS Publications
Length: 363 pages
Size: 6.08 MB
Language: English

B IOLOGISTS HAVE LONG RECOGNIZED the specificity of various insects for
plants and the related interactions between plants and herbivorous insects.
A degree of understanding has evolved from the realization that.different
kinds of insects respond differentially to various secondary chemicals occurring
in plants. It has also been recognized that plants and insects coevolve,
and the continuing adjustments of one to the other reflect the biosynthesis
of defensive compounds b th plant d th development f detoxificatio
or avoidance mechanism
ship is illustrated by the ability of insects to induce detoxifying mechanisms
within twenty-four hours when challenged by a toxic agent. Plant injury, in
turn, can elicit the biosynthesis of additional quantities of resistance agents.
The resources that plants can muster for defense when attacked by
insects are limited. Plants that stand exposed to insects over long periods
generally develop defense systems that require a relatively large quantity of
the resistance agent(s), and these agents often bind dietary protein or otherwise
interfere with digestion. In this case, the costs of defense are relatively
large and so the yield may be decreased. Plants that are exposed to pests over
a short period generally develop defense systems that involve the biosynthesis
of a small amount of a highly toxic agent. Although such defense
systems require that the plant divert less energy from yield to defense, in
evolutionary time the insect may be able to adapt to the plant and defeat
the resistance.
Of the expressions of plant resistance that are chemical, the so-called
secondary plant compounds appear to be dominant. In most cases they
modify or control insect growth, development, and reproduction, but others
such as the antifeedants modify behavior. However, antifeedants may also
be toxicants and toxicants may also be antifeedants; thus their designation
is a function of the bioassay employed. Not all compounds toxic to one
insect are toxic to another. In evolutionary time, some insects develop
mechanisms by adaption to detoxify compounds in plants on which they
must feed whereas others do not. As a result, a compound toxic to one
insect may be a feeding stimulant for a second. To the extent that the biosynthesis
of the compounds is an expression of genetic information, the
elucidation of the compounds and their roles can provide a guide to selections
by plant breeders. Additionally, as genetic studies become more
sophisticated, the assignments of the role of individual genes in directing
biosynthesis of resistance compounds will be expediated. Eventually,
improved knowledge about genetic engineering will provide the technology
for introducing protective genes into crop plants, thus creating resistant
The book is divided into four sections: Ecological and Histochemical
Aspects, Biochemical and Physiological Mechanisms, Insect Feeding Mechanisms,
and Roles of Plant Constituents. It is hoped that this volume will
help to identify unifying themes by which plants express resistance to
insects. With an ever increasing world population exerting greater and
greater pressure on food production systems, every potential breakthrough
is of critical importance.

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