Leaf structure of tobacco in vitro grown plantlets as affected by saccharose and irradiance

Tobacco plantlets were cultured in vitro under high (200 mu mol m(-2) s(-1) ) or low (60 mu mol m(-2) s(-1)) irradiance with or without saccharose in t he medium. Light microscopy and image analysis were used to evaluate the ef fect of these culture conditions on leaf anatomy. Addition of saccharose re sulted in thicker leaves (all leaf layers) and larger mesophyll cells under both growth irradiances. Various irradiance affected leaf anatomy differen tly when plantlets had been cultivated in presence or absence of saccharose in the medium. While under high irradiance in presence of saccharose leaf thickness and number of chloroplasts per cell section were increased, plant lets grown under high irradiance in absence of saccharose had thinner leave s and less chloroplasts per cell section. The changes were more pronounced in palisade parenchyma layer.