Aluminium Induced Magnesium Deficiency in Oats

Abstract

AbstractIt was the objective to study the effect of Al on Mg uptake by plants, precluding as far as possible the effect of Al on root growth.Oat plants were grown in a complete standard nutrient solution without any differential treatment, in order to obtain a set of plants which did not differ in the size, the morphology and the physiology of the root system. After the first harvest at the beginning of the stem elongation stage 4 different treatments were introduced: pH 5.5‐6.0, pH 5.5‐6.0 without Mg, pH 3.8‐4.1, pH 3.8‐4.1 + 0.3 mmole Al/l. Apart from these variations the composition of the nutrient solution remained unaltered. After another 10 days 2 vessels of each treatment were harvested. The final harvest was 14 days after the beginning of the differential treatments.The growth (in terms of dry matter yield) of neither the shoots nor the roots was adversely affected by the differential treatments, although the plants in the Al and Mg0 treatments showed distinct symptoms of nutritional disorder. The plants in the low and the high pH treatments differed neither in Mg uptakte nor in Mg concentration in the plants. However, the addition of Al to the nutrient solution reduced Mg uptake in the shoots to about 30% of that in the Al0 treatments, while there was a net loss of Mg in the roots in spite of the fact that dry matter increased. This means that net uptake of Mg was less than was translocated to the shoot during the period of differential treatments. With no Al in the nutrient solution the Mg concentration in the shoots declined by 3–8% between the first and the final harvest, whereas it increased by 22–35% in the roots. If, however, Al was added to the nutrient solution the Mg concentration dropped by 46% in the shoots and 70% in the roots. With the exception of Ca in the roots, the differential treatments had no effect on the uptake and concentration of Ca, K and P in the plants.In terms of dry matter the differential treatments did not influence root growth and it was concluded that Al had a direct effect on Mg uptake by either inactivating or competing for uptake sites or carriers.