Environmental Factors Affecting Organisms

The environment affects an organism in many ways, at any time. To understand the reactions of a particular organism in a certain situation, certain environmental factors are taken into concern, separately, if possible. These factors controlling stress conditions alter the state of equilibrium in the organism and lead to a series of morphological, physiological, biochemical and molecular changes in the organism i.e. plants, which adversely affects their growth, vigor and yield. Thus, plant stress has been defined by Lichtenthaler (1996) as ‘any unfavourable condition or substance that affects or blocks a plant’s metabolism, growth or development.’ [1]. The primary cause of crop loss worldwide, reducing the average yield of major crop plants by 50% is due to abiotic stresses [2]. When a threat is identified or realized, the plant is in a state of ‘alarm’. If this stress persists, the organism enters into the ‘resistance’ phase where it attempts to cope up with mechanisms of protection and defense. In the ‘exhaustion’ phase, the organism’s resources are eventually depleted and the organism is unable to maintain normal function so

It posits that, a body is deformed if it is stretched by a force .i.e. stress. This ‘deformation’ can at first be reversible, but if the force or stress intensifies, deformation continues and the body finally breaks down [3]. However, when this concept is applied to a biological system, like plants, the following important parameters are taken into account:

• Time factor: In a biological system, the amount of stress is the product of the intensity of stress and duration of stress [2]. Upon a long duration (persistent) stress, plants may adapt and develop morphological and physiological changes, but if this stress continues and intensifies, the plant responds by change in gene expression (Figure