EFFECT OF CALCIUM AND MAGNESIUM ABUNDANCE IN NUTRIENT SOLUTION ON ALUMINUM TOXICITY IN WINTER-WHEAT

It is suggested that Al affects Ca homeostasis in plants. In our work we have studied the effect of Ca : Mg molar ratio in nutrient solution on the growth parameters of wheat (Triticum aestivum L., cv. Sparta) in the presence of Al. If Al causes reduction of Ca2+ uptake and so Ca homeostasis is disturbed, it would be possible to alleviate Al-toxici ty by increasing Ca2+ concentration in nutrient solution. This will ch ange the Ca : Mg ratio what can lead to changes in the plasmalemma per meability. As the control variant we used Ca : Mg ratio 2 : 1, which i s very near to Ca : Mg ratio in Knop nutrient solution. The ratio Ca: Mg 5 : 1 was used to increase Ca2+ concentration and Ca : Mg 1 : 4 rat io was used to increase Mg concentration. Total concentration of Ca Mg ions in the nutrient solution was 5,7.10(-3) M. Al was used in the form of Al-2(SO4)(3), 7.4.10(-4) M, pH 4 of nutrient solutions was adj usted with HCl. Supplement of Ca2+ in the variant with Ca : Mg 5 : 1 r atio in the presence of Al caused decrease in longitudinal growth of r oots when compared with the control variant (Fig. 2). Ca content in th is variant increased in the roots, but Ca supplement had no effect on the Al content in whole plants (Figs 5, 6). In the case of increased M g concentration (Mg : Ca 4 : 1) in the presence of Al longitudinal gro wth of roots decreased even more (Figs 3, 4). It had no effect on the Ca content in roots, while in shoots Ca content slightly decreased (Fi gs 5, 6). This would indicate that Al-toxicity was not induced by Ca a nd Mg deficiency. Our results did not confirm alleviating effect of Ca supplement in nutrient solution on Al-toxicity if there is constant l ow pH. These are more in agreement with the results of Grant, Racz (19 90), who found increased efflux of K+ from the roots of barley in case of changed Ca : Mg ratio in both directions. According to these findi ngs we suppose that disturbance of plasmalemma semipermeability of whe at root tissue would be the primary effect of Al-toxicity.