The Effect of Salinity on Growth, Inorganic Ions and Dry Matter Partitioning in Sugar Beet Cultivars

Abstract

This study investigated intra-specific variation in the growth parameters and dry matter partitioning of sugar beet cultivars at different levels of salinity (0, 50, 150, 250 and 350 mM NaCl + CaCl2 in 5:1 molar ratio) using four cvs, one British (Madison) and three Iranian cvs (7233-P12, 7233-P21 and 7233-P29). The plants were grown in a controlled greenhouse environment for about 18 weeks. Although growth parameters such as leaf area and dry matter accumulation were stimulated or unaffected at a low level of salinity (50 mM), higher salt concentrations significantly decreased all growth traits. At a high level of salinity, cv P29 showed a significantly higher leaf area and total dry matter than others at 16 weeks of salt treatment. Pre-dawn leaf-water potential (ΨL) and shoot water content (SWC) were decreased by salinity. Cvs Madison and P12 had significantly lower ΨL (more negative) and shoot water content at high levels of salt treatment (250 and 350 mM), while P29 and P21 showed higher ΨL (less negative) and shoot water content at the same salt concentrations. Analysis of ion accumulation revealed that Na+ and Cl- contents were greatly increased in leaves under saline conditions. However, salt tolerant P29 had lower Na+ and Cl- concentrations than other cvs at high levels of salinity. The root dry matter of sugar beet cvs at the lowest and the highest salt concentrations reduced by 23.3% and 89.8%, respectively compared to the non-stressed plants, while shoot dry matter decreased by 1.1% and 77% at the same salt concentrations, respectively, after 16 weeks of salt treatment. The pattern of dry matter partitioning to different parts of the plant was changed by salt stress and the dry matter allocated to the storage roots was reduced by 6% and 18% at the lowest and the highest salt concentrations, respectively, at 16 weeks after salinisation.