I am thinking about Rainer Hedrich's model for malate regulation of the GCAC1,
guard cell anion channel 1, and I wonder where the external malate is coming
from. I understand that it comes from mesophyll cells, but why? Do they convert
it from OAA and then export it to the substomatal cavity?
Also, wouldn't malate be expected to comeout of the peroxisomes if there was
too little CO2 and the C2 pathway were taking place?