Adaptational Traits That Resist and/orTolerate Drought

Abstract

The terms “tolerance” and “resistance” are usually employed interchangeably and loosely. Before we discuss the traits that help desert plants to tolerate and/or resist drought, it is necessary to evaluate these two terms within the present context. Drought tolerance means the degree to which a plant can successfully withstand the effect of drought. This occurs as a result of the innate characteristics of the plant. It may mean that a plant does not exhibit modifications or changes in its structure or function to do so. This can be considered to be a passive response. Resistance has another meaning — it is an active response to the factor affecting the plant. Drought resistance can be understood to mean that the plant remains unharmed by the drought through various adaptations and traits. These traits can be modified and/or maximised according to the degree of severity, and the duration and the length of the drought. In order to live under desert conditions, plants in general possess the characteristics of both tolerance and resistance to drought. It seems probable that resistance traits come into action when tolerance traits have reached full capacity. In other words, when a plant is subjected to stress, its tolerance characteristics oppose this stress. As the stress increases, the activity of tolerance traits continues to rise in opposition. At a certain threshold, the tolerance capacity becomes insufficient to withstand the stress. At this stage, the resistance traits are initiated. The response of these traits can be short-term or long-term, according to the severity and duration of the stress. Every species has its own potential for tolerating and resisting drought. When grown under different environmental conditions, different individuals of the same species exhibit different degrees of resistance. The drier the conditions, the greater the degree of resistance manifested. This is due to the fact that desert plants are flexible as regards their response to drought. They are endowed with many adaptational traits and characteristics that help them to tolerate and resist drought.