Introduction to Ecological Biochemistry

J. B. Harborne

• Publisher: Academic Press
• Year: 2014
• ISBN:
  9780080918594
• Edition: 4
• Topic: Biowissenschaften
• Subtopic: Ökosysteme & Lebensräume

Ecological biochemistry concerns the biochemistry of interactions between animals, plants and the environment, and includes such diverse subjects as plant adaptations to soil pollutants and the effects of plant toxins on herbivores. The intriguing dependence of the Monarch butterfly on its host plants is chosen as an example of plant-animal coevolution in action.

The ability to isolate trace amounts of a substance from plant tissues has led to a wealth of new research, and the fourth edition of this well-known text has consequently been extensively revised. New sections have been provided on the cost of chemical defence and on the release of predator-attracting volatiles from plants. New information has been included on cyanogenesis, the protective role of tannins in plants and the phenomenon of induced defence in plant leaves following herbivory.

Advanced level students and research workers aloke will find much of value in this comprehensive text, written by an acknowledged expert on this fascinating subject.

• The book covers the biochemistry of interactions between animals, plants and the environment, and includes such diverse subjects as plant adaptations to soil pollutants and the effects of plant toxins on herbivores
• The intriguing dependence of the Monarch butterfly on its host plants is chosen as an example of plant-animal coevolution in action
• New sections have been added on the cost of chemical defence and on the release of predators attracting volatiles from plants
• New information has been included on cyanogenesis, the protective role of tannins in plants and the phenomenon of induced defence in plant leaves following herbivory

1

The Plant and Its Biochemical Adaptation to the Environment

Publisher Summary

This chapter presents an account of the explosive development in ecological biochemistry that has occurred in the last two decades. Ecology is largely observational, is concerned with interactions between living organisms in their natural habitats, and is carried out in the field. By contrast, biochemistry is experimental, is concerned with interactions at the molecular level, and is carried out at the laboratory bench. Nevertheless, these two distinctive disciplines have cross-fertilized in recent years with astonishing success and a whole new area of scientific endeavor has opened up as a result. To the ecologist, knowledge of biochemistry has illuminated to a remarkable degree the complex interactions and co-evolutionary adaptations that occur between plant and plant, plant and animal, and animal and animal. Similarly, to the biochemist, studies in ecology have provided for the first time a rational and satisfying explanation for at least a part of the enormous proliferation of secondary metabolism that is observed in plants. The chapter discusses the types of environmental factors that plants are subject to. It also discusses the biochemical bases of adaptation to climate, saline habitats, soil, and high concentrations of toxic metals in soils.

I Introduction

II The biochemical bases of adaptation to climate

A General

B Photosynthesis in tropical plants

C Adaptation to freezing

D Adaptation to high temperatures

E Adaptation to flooding

F Adaptation to drought

III Biochemical adaptation to the soil

A Selenium toxicity

B Heavy metal toxicity

C Adaptation to salinity

IV Detoxification mechanisms

A General

B Detoxification of phenols

C Detoxification of systemic fungicides

D Detoxification of herbicides

V Conclusion

Bibliography

I Introduction

The marriage between such diverse disciplines as ecology and biochemistry may seem at first a curious alliance. Ecology is largely observational, is concerned with interactions between living organisms in their natural habitats and is carried out in the field. By contrast, biochemistry is experimental, is concerned with interactions at the molecular level and is carried out at the laboratory bench. Nevertheless, these two distinctive disciplines have cross-fertilized in recent years with astonishing success and a whole new area of scientific endeavour has opened up as a result. Ecological biochemistry is only one of a variety of phrases that have been employed to describe these exciting developments.

To the ecologist, knowledge of biochemistry has illuminated to a remarkable degree the complex interactions and co-evolutionary adaptations that occur between plant and plant, plant and animal and animal and animal. It has led to the realization, for example, that plants are functionally interdependent with respect to their animal herbivores and form what are termed ‘plant defense guilds’ (Atsatt and O’Dowd, 1976). Similarly, to the biochemist, studies in ecology have provided for the first time a rational and satisfying explanation for at least a part of the enormous proliferation of secondary metabolism that is observed in plants. Much of the purpose of the synthesis of complex molecules of terpenoids, alkaloids and phenolics lies in their use as defence agents in the plant’s fight for survival against animal depredation.

The aim, therefore, of the present text is to provide an account for the student reader of the explosive development in ecological biochemistry that has occurred in the last two decades. The various chapters deal in turn with the plant and its interactions with animals and with other plants, while animal-animal interactions are considered in some detail in Chapter 8. It should be emphasized at this point that the biochemistry of many interactions has been deliberately simplified here in order to present a coherent story. It must be recognized that a given interaction between a plant host species and its animal predator species can be very subtle and complex and certain aspects of such an interaction may require many years of study before all is revealed. Furthermore, a third organism may have a controlling influence on a plant–animal interaction, such as a parasitoid of the animal or a microbial infection of the plant.

The term plant is generally used throughout this book to refer to higher plants and mainly to angiosperms, gymnosperms and ferns. Fungi, bacteria and viruses will usually be referred to as micro-organisms; other groups of plants will rarely be mentioned—i.e. algae, mosses and liverworts—largely because their ecological biochemistry has not yet been studied in much detail.

The selection of animals mentioned in this text is restricted to those taxa that have been studied experimentally and is certainly very unrepresentative of the animal kingdom as a whole. This is because plant-animal interactions in terms of feeding and defence have largely centred on the insect kingdom and only more recently have biochemical aspects of mammalian ecology been explored to any extent.

The emphasis here on the plant is due, at least in part, to the fact that plants are richer than animals in their biochemical diversity. Although secondary metabolism occurs in animals (Luckner, 1990), nevertheless, over four-fifths of all presently known natural products are of plant origin (Robinson, 1980; Swain, 1974). Some idea of the range of secondary compounds found in plants can be obtained from Table 1.1, which lists some of the major classes, together with an indication of numbers of known compounds, distribution patterns and biological activities. Many of these substances will be mentioned in more detail in subsequent chapters. The richness in secondary chemistry in plants is at least partly explicable by the simple fact that plants are rooted in the soil and cannot move; they cannot respond to the environment in ways open to animals.

Table 1.1

Major classes of secondary plant compounds involved in plant–animal interactions

Class	Approx. number of structures	Distribution	Physiological activity
NITROGEN COMPOUNDS
Alkaloids	10,000	Widely in angiosperms, especially in root, leaf and fruit	Many toxic and bitter tasting
Amines	100	Widely in angiosperms, often in flowers	Many repellent smelling; some hallucinogenic
Amino acids (non-protein)	400	Especially in seeds of legumes, but relatively widespread	Many toxic
Cyanogenic glycosides	40	Sporadic, especially in fru...