The anatomic and functional leaf characteristics related to photosynthetic performance of Castanea sativa growing in vitro and in nursery were compared. The irradiance saturated photosynthesis in in vitro grown plantlets was significantly lower compared to nursery plants (65 vs. 722 mu mol m(-2) s(-1)). The maximum photosynthetic rate (P-Nmax) was 4.0 and 10.0 mu mol(CO2) m(-2) s(-1) in in vitro microshoots and nursery plant leaves, respectively. Carboxylation efficiency (C-E) and electron transport rate (ETR) were three-folds higher in nursery plants than in microshoots. The non-photochemical quenching (NPQ) was saturated at 80 mu mol m(-2) s(-1) in microshoots suggesting limited photoprotection by thermal dissipation. The microshoots had wide open, spherical stomata and higher stomatal density than nursery plants and they had almost no epicuticular wax. Consequently, the microshoots had high stomatal conductance and high transpiration rate. These anatomic and functional leaf characteristics are likely major causes of the low survival rates of plantlets after ex vitro transfer.