[Ecophysiology] Water Stress, Osmotic stress, Salt Stress (MPa)

[southdown5]

Hi there,

I have a question regarding different units being used in plant physiology for measurement of different stresses

e.g 10 % of MPa PEG
        -0.3 MPa of PEG
           0.5 mM Salt.
        
why some people measure water stress in percentage other in MPa or mM. Are they interconvertible ?. if yes what does a 10 % of MPa PEG means ? what its equivalent in MPa ?


could some can elaborate the whole concept please and how to convert one unit to another ?


Thanks in advance.

R