using the exported variable after su

Shell Programming and Scripting
1

Dear All,How can use a variable which I have exported when I am logged into one user to be used once I su to another user.something like 1.Login to Unix box as user12. export var1="TEST"3. su - user24. User the var1 value ( it should return TEST)I have checked just export does not work. any other way we can do this.I am talking about Solaris.cheers,

2 
>PLPL="hi"
>export PLPL
>su root
> echo $PLPL
> exit
> su - root
>echo $PLPL

>

The difference between su - and su