Stereological analysis of the sunflower root seedling

Abstract

The aim of this research was to determine the histological basis of the genotypic differences for drought tolerance, calculate tissue volume densities (Vv), examine the variability, and assess tissue proportions along the root maturity gradient. For the stereological analyses of root tissues four sunflower genotypes, 14 days old seedlings which were grown in rhizotrons, have been carried out on the primary (axial) root. The total length of the axial roots varied among genotypes, but not significantly. Root cross-sections were cut along the root maturity in five segments according to the principle of systematic uniform random sampling method. Cross-sections were made applying cryo-technique procedure and proportion of tissues was estimated by point-counting method. The vessel network characteristics (number and diameter of vessels) vary along maturity gradient and individual roots. Consequently, branching vessels pattern and axial conductance may limit water flow through root systems.