Osmotic adjustment in sugar beet plant under salinity stress

This study was carried out in the General Commission for Scientific Agricultural Research (GCSAR) at Der Ez Zour Agricultural Re-search Center, during 2009- 2010 growing seasons. The role of Na+, K+, Na+/K+, carbohydrates accumulation of leaves, and sugar content of roots on the osmotic adjustment was studied in 10 sugar beet genotypes (five were monogerms and five were multi-germs), under salinity stress. Sugar beet plants were irrigated with saline water, with the electrical conductivity (EC) ranging from 8.6-10 dS.m-1 in the first year and 8.4-10.4 dS.m-1 in the second year. A randomized complete block design (RCBD) with three repli-cates was used. The results showed that Na+ content in leaves and roots of all genotypes was increased in salinity stress, but the increment in leaves was higher than in roots. K+ contents in leaves and roots were decreased in all genotypes, but this reduction was lower in roots as compared with leaves. This may be due to the substitution of Na+ with K+ in such condition. However, under salinity stress concentrations of inorganic solutes (Na+, and K+) in leaves was higher than those in roots. Kawimera (multigerm) was considered the most tolerant genotype because of high Na+ content in its leaves and roots, whereas the most sensitive geno-type was Tigris (multigerm), which had the lowest content of Na+ in leaves and roots. Generally, the accumulation of soluble sug-ars in leaves was higher in tolerant genotypes as compared with non-tolerant ones. The results exhibited no correlation between sugar content in roots and salinity stress. Correlation analysis showed Na+ content followed by soluble sugars as the main solutes for osmotic adjustment in sugar beet leaves under salinity conditions. Moreover, both sucrose and Na+ contents in beet root could be considered the main solutes for osmotic adjustment.