Turkish Journal of Botany




This study was carried out to investigate the ameliorative effects of salt pretreatment against B toxicity in two sunflower cultivars (Helianthus annuus L. `Sanbro? and `Tarsan-1018?) differing in salt tolerance. Seedlings were grown in perlite with modified half-strength Hoagland?s solution for 15 days and then they were divided into two groups: salt-pretreated (75 mM NaCl for 5 days) and B-treated (control, 2, 4, and 8 mM B for 10 days). In both cultivars, the biomass of root and shoot decreased depending on B accumulation, especially at 8 mM. The translocation factor values indicated that B uptaken by roots of the genotypes were translocated to the leaves. High B accumulation adversely affected the water balance and membrane integrity of the leaves. Additionally, toxic B levels caused changes in the some JIP tests and slow fluorescence parameters (ABS/RC, TR0/RC, ET0/RC, RE0/RC, DI0/RC, Area, ?E0, ?R0 and jD0, ?PSII, ETR) of both cultivars and these changes led to a significant decrease in photosynthetic performance (PIABS and PITOTAL). Salt pretreatment ameliorated the damaging effects of toxic B on membrane integrity, water content, and the photosynthetic process; decreased B accumulation; and improved the membrane stability. Both cultivars acquired tolerance against B toxicity with salt pretreatment and survived in increasing boron toxicity. We conclude that sunflower can be used for phytoremediation purposes for boron-contaminated soils. Additionally, this study is the first report to reveal that moderate salt stress pretreatment alleviates B toxicity and provides tolerance to B. This alleviation might be achieved by NaCl to decrease the boron uptake from the roots.


Boron toxicity, JIP test, photochemical activity, salt pretreatment, slow and fast chlorophyll a fluorescence, sunflower (Helianthus annuus L.)

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