Re: what do sucrose usually do to chloroplasts?

I didn't know the answer to this one, so I asked a plant physiologist 
friend. She said that sucrose is used as an osmotic stabilizer so that 
the chloroplast doesn't disintegrate. In other words, the buffer just 
uses sucrose as a convenient large molecule that won't cross the 
membrane, not for any particular biological activity. Other molecules 
with the same properties, such as polyethyleneglycol, can be used instead.