Plasmodesmata between mesophyll and bundle sheath cells in relation to the exchange of C4-acids.

In the C4 species Salsola kali L. the frequency of plasmodesmata in the wall between mesophyll and bundle sheath cells has been determined with great precision by the use of transmission and scanning electron microscopy. The frequency of 14×10(8) cm(-2) is rather high compared to values from other plant tissues, but if it is assumed that the postulated exchange of C4-acids occur in the desmotubulus of the plasmodesmata, the fraction of the mesophyll-bundle sheath interface occupied by plasmodesmatal pores is 10-10(2) times smaller than previously thought.