Encyclopedia of Environmental Science and Engineering, Volume I and II

244

E

EARTH–SPACE ORGANIZATION: see THE TERRESTRIAL SYSTEM

ECOLOGY: see ECOSYSTEM THEORY

ECOLOGY OF FISH: see POLLUTION EFFECTS ON FISH; THERMAL EFFECTS

ON FISH ECOLOGY

ECOLOGY OF HUMANS: see EFFECTS OF CHEMICALS; HAZARDOUS

WASTES

ECOLOGY OF PLANTS

Ecology is the study of the relationship between organisms

and the environment and the interrleationships between

organisms. The response of an organism to the environ-

ment is determined by the effects of the environment on

the processes in the organism. Stated in another way, all

environmental factors affect the growth and distribution

of organisms only by affecting rates of processes in the

organisms. The study of the effects of environmental fac-

tors on processes in organisms is physiological ecology, or

in other words, it is the study of the physiological basis of

ecological behavior. This field obviously represents a mar-

riage between ecology and physiology, and is sometimes

called environmental physiology. The field of physiological

ecology is extremely broad: thus, this paper is restricted to

certain aspects of physiological plant ecology.

ENVIRONMENTAL FACTORS

The environment is very complex, consisting of all influences

external to an organisms. Many systems have been devised

to classify the environment but space does not allow a dis-

cussion here. The following list of specific environmental

factors is a satisfactory one although the list could obviously

be subdivided in many ways:

1) water

2) temperature

3) radiant energy

4) essential elements

5) aeration

6) toxins

7) wind

8) topography

9) nature of geologic strata

10) altitude

11) organic matter content of soil

12) texture and structure of soil

13) base exchange capacity of soil

14) color of soil

15) plant growth regulators

16) soil organisms

17) parasites

18) plants and animals other than above.

Even cursory examination of this list makes it clear that

the effects of all these factors on processes in plants could

not be discussed in a brief survey. For example, thorough

coverage of the effects of the various essential elements on

plant processes would require a sizeable manuscript. I have

decided, therefore, to discuss a few factors in sufficient depth

to give the reader a feeling for the area.

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