The effect of Al and Mn on growth and mineral composition of Casuarina equisetifolia Forst

Abstract

In pot experiments (perlite) with Casuarina equisetifolia a strong growth depression and clear Al and Mn toxicity symptoms were found with higher treatment levels of Al and Mn. In nutrient solution dry matter yields at the highest Al treatment (2000 /µM) were 37,5% for shoot and 49,5% for root biomass compared to the control. With the highest Mn treatment (3200 /µM) the yield was 49% of control for both shoot and root dry matter. The lowest levels of Al and Mn treatments (250 µM Al and 400 /µM Mn) resulted in a dry weight production of 78,6% for shoots and 99,3% for roots in the case of Al and 80,7% for shoots and 89,8% for roots in the case of Mn compared with the dry weight produced by control plants. The Al accumulation was relatively higher in roots than in shoots and increased with increasing Al concetrations in the nutrient solution. Also, Mn content in roots under low Mn treatments was as high as in shoots. High Al and Mn concentrations had a negative effect on the uptake of cations (Ca, Mg and Na). Aluminium had no effect on K uptake. A high decrease in the phosphorus concentrations in shoots and roots occurred in the higher treatments of Mn and especially Al. The uptake of NO3-N from the nutrient solution was positively influenced only by the lower Al and Mn treatments. Higher concentrations of Al and Mn had no effect on the N uptake. The principal toxicity symptoms shown by the plants were the blue-green colour with brown-necrotic spots on their shoots for Al and white-chlorotic spots in the upper parts of the shoots for Mn.