In order to investigate the solutes accumulation associated with salt tolerance of rice (Oryza sativa L.), two rice genotypes including IR651 (salt-tolerant) and IR29 (salt-sensitive) were grown hydroponically in the Youshida nutrient solution. Salinity treatment was imposed 3 weeks after sowing using NaCl in two levels 0 and 100 mmol. Samples were separately collected from the youngest (sixth) leaves, leaf sheaths and roots at 72 and 240 h after salinization; then Na + , K + , Ca 2+ , Mg 2+ , P, Mn 2+ , Cl -and total soluble sugars concentration and Na + /K + ratio were determined. Total dry weight of both genotypes decreased with the application of NaCl. Salinity caused higher accumulation of Na + and Cl -in the sixth leaf and leaf sheath of IR29 than in IR651 while their concentration in root of IR651 was higher. K + concentration was decreased in the sixth leaf and leaf sheath of IR29 under NaCl stress. Reduction in Ca 2+ and Mg 2+ concentrations were observed in sixth leaves of both genotypes. P concentration was increased in leaf sheath and root of IR29 under saline conditions while it showed no changes in IR651. Our results indicated that the tolerant genotype had mechanisms to prevent high Na + and Cl -accumulation in the sixth leaf. High total soluble sugars concentration in shoot of IR651 is probably for adjusting osmotic potential and better water uptake under salinity. These mechanisms help plant to avoid tissue death and enable to continue its growth and development under saline conditions.
In order to investigate the effects of water stress and different levels of N fertilizer on yield and water use efficiency in sugar beet (Var. BP) a split plots based on randomized complete block design was carried out with 4 replications in Khorasan Agricultural and Natural Resources Research Center (KANRC) during cropping season in 2006. Water treatments comprising three levels including control (without water stress), initial water stress and continuous water stress as main plots and different amounts of N fertilizer in 4 levels vis: control (0), 50, 100 and 150 Kg net N. ha-1 as sub plots were assessed. Analysis of variation showed that effects of water treatments on root yield and gross sugar content was significant (at 1% level). Different levels of N also have significant effect on root yield, net and gross sugar percent at 1% level while didn't influence net sugar yield significantly. Interaction of water and N wasn’t significant for all the traits. Water use efficiency for root (WUEr) and for sugar (WUEs) were significant in irrigation amounts (P< 0.05) However, results showed that increased root yield under no water stress conditions with increased N amount was much more than it in water stress conditions. In terms of root yield, no water stress treatment using 150 Kg Net N.ha-1 had the highest yield. But water stress treatment particularly constant water stress, caused the maximum water use efficiency.
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