INTRODUCTION

Plants are exposed to unusual, even extreme, environmental conditions, daily, seasonally, or from time to time depending on where they live. Beneath the benign face of the natural green world, plants are waging battles constantly against difficulties posed by their environments. Because these stresses often lead to reduced health in plants, just as they do in animals, they are also of considerable interest to agricultural scientists. Stressed crops usually produce lower yields. Understanding how plants cope with and respond to environmental stresses (often called abiotic stresses to distinguish them from those caused by diseases and predators, which are biotic stresses) is, therefore, important to breeders whose job it is to develop crop varieties with resistance to stresses while maintaining high yields.

WHAT IS STRESS?

The word stress was used first by engineers to explain what happens when a force is applied to an object; strain is the change in the object caused by the stress. For example, an elastic band can be stressed by forcing it to expand; strain is how much the band is stretched by the force applied. Stresses and strains in the physical world can often be precisely applied and measured.

DEFINING “BIOLOGICAL” STRESS AND STRAIN

In a cultivated context

Anything that does not allow a plant to reach its full potential is a stress which will have a consequent strain, such as lower growth or seed production.