Root xylem anatomy of the wild and cultivated sunflower

The root functionality is affected by numerous factors. One of the main structural parameters, the most important for functionality and adaptability, is xylem organization. Taking into account that sunflower root features have not been directly selected in breeding programs the aim of this research is to determine whether different sunflower genotypes (wild annual species and cultivated genotypes) have influence (i) on the structure of the xylem anatomy and (ii) on the xylem features along the maturity gradient. For the detailed anatomical characterization of root xylem, 14 days old seedlings which were grown in rhizotrons, have been carried out on the primary root. Root cross-sections were cut in positions sampled according to the principle of systematic uniform random sampling method. Along the root maturity, three sections per roots were made using cryotechnic procedure. Observations of the root and measurements of the vessels were carried out using the light microscope with Image Analyzing System. The obtained results of the comparative root xylem anatomy revealed significant phenotypic variability among tested genotypes. The ratio of cross-section xylem area, vessel diameter and theoretical hydraulic conductance (kh), increase along the maturity gradient for all genotypes. Significant differences in vessel size and frequency were recorded between wild species and cultivated genotypes