Relationship between CO2 assimilation and leaf anatomical characteristics of two grapevine cultivars

The possible implication of leaf anatomical characteristics on the photosynthetic rate was studied in two grapevine cultivars, Ribier (Vitis vinifera L.) and Isabella (Vitis labrusca), grown under field conditions. Ribier exhibited higher photosynthetic rates than Isabella, although there were no significant differences in the Rubisco activity and the stomatal conductance. The fraction of mesophyll volume represented by the intercellular spaces as well as the surface area of mesophyll cells exposed to intercellular air spaces were significantly lower in Isabella. Both gaseous CO2 conductance through intercellular airspaces and liquid phase conductance were significantly higher in Ribier than in Isabella, contributing to a higher photosynthetic rate in this cultivar.