Stress is a generic term in biology.
Stress can be heat, cold, mutagens, redox, too little nutrient, too much nutrient, too little oxygen or too much, high or low osmolality, etc.
They aren’t referring to the emotion elicited by an Obama speech.
“osmolality”
I’d add that to my working vocabulary but I’d never be sure when it should be ‘osmolality’ and when it should be ‘osmolarity.’