Q.What is Zero Stress?

Step 1. Recall the concept of the range of tolerance. Every organism can survive an abiotic factor (such as temperature, salinity, or pH) only between a minimum and a maximum limit; outside this range, the organism cannot survive. Within this range, performance (growth, reproduction, activity) is not uniform — it is poor near the extremes and best somewhere in the middle.

Step 2. Define zero stress within this range. The point or narrow zone at which the factor is closest to the organism's physiological optimum is called the point/zone of zero stress — here the organism does not need to invest extra energy in tolerance mechanisms (such as osmoregulation, thermoregulation, or enzyme adjustments) because the surrounding conditions already match its ideal requirements. …

Apply the concept of an organism's range of tolerance for an abiotic factor, identifying the optimum zone within that …

• Confusing zero stress with the entire range of tolerance rather than just its optimum zone …