Drought in acid soil increases aluminum toxicity especially of the Al-sensitive wheat

Abstract

In field conditions crops growth are usually under influence of many abiotic stresses that simultaneously affect their growth. Due to large areas of cultivated lands that are prone to anthropogenic or natural acidification and increasing frequency of drought events the exposure of crops to the simultaneous action of aluminum (Al) toxicity and water deficit is a serious threat decreasing food productivity. The effect of simultaneous soil drought and aluminum toxicity on wheat was studied to determine whether complex alteration within plants in response to drought affects the mechanism of Al tolerance in wheat.Al-tolerant (ET8) and Al-sensitive (ES8) wheat (Triticum aestivum L.) near isogenic lines (NILs) were grown in acid and limed soil under controlled laboratory conditions with precisely controlled water deficit.Although both NILs of contrasting resistivity to Al were characterized by similar root biomass in soil of pH 4.2, the tolerant line was characterized by 60% longer roots. This effect resulted from enhanced contribution of the thick root fractions in ES8. The NILs response to the drought in acid soil was characterized by the higher transpiration from ET8 than ES8 leaves irrespectively of leaf order and the effect was stronger with soil drying. The gap in the performance of both NILs in acid soil was increasing with the decrease in soil water potential.It was also shown that aluminum uptake through root surface area is increasing with the decrease in water uptake and the effect was most pronounced for sensitive line grown in acid soil.