The effect of Chromium VI on leaf water potential (ψw), solute potential (ψa), turgor potential (ψp) and relative water content (RWC) of primary and first trifoliatc leaves of Phaseolus vulgaris L. was studied under normal growth conditions and during an artificially induced water stress period in order to establish the possible influence of this heavy metal on the water stress resistance of plants. Plants were grown on perlite with nutrient solution containing 0, 1⋅0, 2⋅5, 5⋅0 or 10⋅0 μg cm−3 Cr as Na2Cr2O7.2H2O. The effect of Cr on water relations was highly concentration dependent, and primary and first trifoliate leaves were affected differently. The growth reducing concentrations of Cr (2⋅5, 5⋅0 and 10⋅0 μg cm−3) generally decreased ψs and ψw and increased ψp in primary leaves. The 1⋅0 μg cm−3 Cr treatment did not affect growth, but altered water relations substantially: in primary leaves ψw and ψp were increased and ψs decreased, while in trifoliate leaves the effect was the opposite. All Cr treated plants resisted water stress for longer than control plants. The higher water stress resistance may be due to the lower ψs and to the increased cell wall elasticity observed in Cr VI treated plants.

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