Effect of Salt Stress on Growth, Photosynthesis, Gas Exchanges and Chlorophyll Fluorescence Insugar Beet(Beta vulgaris L.) Cultivars in the Seedling Stage under Controlled Condition

According to continuing of drought phenomenon, global warming and dust storms resulted in salining increasing of arable lands, because it’s necessary to know some physiological mechanisms in sugar beet under salt stress,this experiment was conducted to investigation of effect of salinity on growth characteristics, respiration, gas exchange and photosynthesis in three sugar beet cultivars (BR1, Jolgeh and Rasoul) in the 2010 growing season, in greenhouse of Shahid Chamran University as the factorial design based on randomized complete block with three replications.35 days sugar beet seedlings were kept for eight weeks under three salinity levels including control (zero), 100, and 200 mM sodium chloride (NaCl). Salinity Stress reduced shoot and root dry matter and leaf area significantly. With increasing of salinity, the rate of photosynthesis (carbon dioxide assimilation), stomatal conductance, and leaf transpiration rate decreased, but respiratory rate, leaf temperature and SPAD value increased. The results showed that Quantum yield of PSII(ФPSII) decreased by increasing of salinity level, meanwhile Non-Photo Chemical Quenching (NPQ) increased.Accordingto theresults, theconcentration of 200mMsodium chloride, had a highnegative correlation betweenrootdry matter(r=-0.95**)stress susceptibility index. Meansanyreductionindry matter accumulationincreasedinstress susceptibility index.Lowerlevelsofstress susceptibility indexshowingmoretolerance of cultivar tosalinity stress. Based on stress susceptibility index (SSI), in the concentration of 200 mM sodium chloride, cultivars Rasoul, BR1 and Jolgeh are tolerant, semi-tolerant respectively and sensitive were identified. In the end, it seems that root dry weight, can be use as a criterion for salinity resistance of sugar beet cultivars.