effects of salt stress on root anatomy and hydraulic conductivity of barley cultivars

a hydroponic experiment was carried out to compare root anatomy and hydraulic conductivity of four barley cultivars including valfajr, karoon, afzal and zarjo under salt stress conditions. the results showed that under salt stress, the minimum diameter of vessels was observed in the peripheral metaxylem of seminal roots of valfajr cultivar and in adventitious roots; karoon with 19±3 µm had maximum diameter of vessels. in all barely cultivars, salt stress affected the diameter of central and peripheral metaxylem vessels more negatively in comparison to the number of the vessels. the mature xylem vessels of the seminal roots of the valfajr and zarjo cultivars had the most lignified cell walls. when the plants were exposed to salt stress, the casparian bands could be detected more in the seminal roots as u-shape and not in the adventitious roots. the lowest lignification thickness of cell wall (0.78 µm) was observed in the central metaxylem vessels of adventitious roots of afzal cultivar under salt stress. also, afzal cultivar with highest surface area and lowest thickness of lignified cell walls, had the highest seminal root hydraulic conductivity (5.84×10-9 m s-1 mpa-1), whereas hydraulic conductivity was decreased to 3.21 and 3.17×10-9 m s-1 mpa-1 in valfajr and zarjo cultivars, respectively. overall, afzal and karoon cultivars were found to perform better in water uptake at the early stages of growth due to less lignified cell walls of xylem in seminal and adventitious roots under salt stress conditions. further research on hydraulic conductivity could be recommended.