Morphological and Anatomical Adaptability of Sorghum Roots Exposed to Water-Deficit Stress during Vegetative Stage.

Agricultural productivity is threatened by scarcity of water and global climate models project increased intensity and magnitude in water-deficit conditions. Understanding the role of root system’s adaptation under water-deficit conditions is crucial for sorghum which is often grown in water-limiting environments. Experiments were conducted in a greenhouse using 1m lysimeter columns filled with turface. The research was conducted on a set of 11 sorghum mapping population parental lines (Ajabsido, SC 1103, SC 265, P898012, SC 35, Macia, SC 283, SC 1345, Segaolane, SC 971 and RTx430 - the common parent). Water-deficit stress (55% to 60% water-holding capacity) was imposed lasting for 15-days, starting from 35-days after emergence. Roots were carefully removed and washed at the end of stress period. To investigate the root anatomical complexity, root sections (3-4 cm) were taken from three different positions along the root length (7 cm from the root-shoot junction, the middle section and 7 cm from the root apex) and section images were obtained using a compound microscope. Morphological root features were determined by analyzing scanned images with WinRHIZO. The rooting depths recorded for stressed and well-watered plants ranged from 138 - 53 cm and 144 - 83 cm, respectively. Meta-Xylem number and size, xylem and stele diameter varied both by tissue position and by treatment. Significant genotypic variability was observed for most root traits. A positive relationship (correlation coefficient, r ≥ 0.50) was found with rooting depth and total root length as well as with root dry weight and total root surface area. Findings were validated using contrasting lines and differential rooting morphological and anatomical characteristics identified will help complement efforts currently ongoing to enhance drought resilience in sorghum.