Physiological Responses And Ion Distribution Of Salix Clone SH31 To Salt Stress

Willow is an important landscaping species. The current study used “SH31”clone of willow to test the physiological response to salinity stress at a half inhibitory concentration of 0.6%Na Cl.Growth rate of “SH31”was decreased, with the strongest inhibition in leaves and least in in roots. The root/shoot ratio was initially decreased but increased as stress sustained due mainly to the higher sensitivity in roots than shoots. Root growth, total root volume, total surface area, and total root length were all lower than the control especially for the roots in the range of 0 to 0.5mm in diameter.Under the salinity stress, net photosynthetic rate were significantly decreased which was contributed to stomatal factors at the early stage and to increased intercellular CO2 concentration atthe latter stages. This was also shown by the decreased photochemical efficiency(Fv/Fm) and chlorophyll content in the leaves.Plant Na+contents were significantly increased and the content of K+ decreased in roots and stems as compared to the untreated control. “SH31” maintained a high K+/Na+ ratio, Ca2+ content and a large amount of salt ions in stems, which is considered as one of mechanisms of salt tolerance.Ten days after the salinity treatment, energy dispersive spectroscopy line scan analysis showed that the leaf content of Na+ and Cl- increased, while K+ decreased. Compared to the control leaves, salinity stress increased Na+ in veins and mesophyll but did not affect the content in the petiole. Root compartmented Na+was higher than Cl-.In summary, the growth and photosynthesis of “SH31” willow decreased under salinity stress. “SH31” responded to salinity stress by transporting salt ions from underground section to aboveground section and maintaining the ion balance in leaves.