Abstract
The effects of cadmium (Cd) on growth parameters and anatomy of tomato (Solanum lycopersicum L.) internodes and leaves differing in age were addressed. Six-day-old seedlings were hydroponically cultivated and exposed for 10 d to increasing concentrations of CdCl(2) (0-100 mu M). Cd restricted both fresh and dry mass of leaves and internodes depending on the tissue age. Morphological changes were observed following Cd-exposure, including the reduction in the internode length and diameter as well as decreasing leaf area and thickness. Stem morphogenesis was altered too, cellular division disorders being associated with abnormal enlargement of both cortical and medullar cell layers. Histological study at the internode level revealed that Cd restricted the expansion of tissues in concomitance with the presence of peculiar structures in the cortical and medullar parenchymas. Furthermore, under high Cd-treatment (100 mu M CdCl(2)), reduction of the mesophyll cell size and spongy intercellular space volume leading to leaf blade thinning was observed. The intensity of the above Cd-induced anatomical changes differed depending on the organ developmental stages at which they were first exposed to the contaminant.