Evaluation of a screening technique for manganese toxicity in relation to leaf manganese distribution and interaction with silicon.

Abstract

A screening technique utilizing a flowing nutrient culture was used to evaluate 20 lettuce cultivars differing in the severity of the toxicity symptoms marginal yellowing and necrosis in older leaves. Growth, leaf and root Mn contents and toxicity ratings (1 = no symptoms to 5 = high toxicity) were recorded over six Mn and two Si concentrations. A test solution of 0.5-1.0 mg/l Mn produced consistent toxicity ratings and the ratings for tolerant and sensitive cultivars were similar to ratings for the same cultivars grown under glasshouse conditions. Total Mn content in leaves was not a useful index for Mn sensitivity. Increased Si resulted in a repression of toxicity symptoms and decreased shoot/root Mn ratios in 12 cultivars. ADDITIONAL ABSTRACT: A screening technique was developed to evaluate lettuce cultivars for manganese tolerance in flowing nutrient culture. Considerable variation in the sensitivity of 20 cultivars was observed, as shown by visible symptoms. However there was no correlation between accumulation of Mn in leaves and roots and the degree of Mn tolerance. Increasing silicon in the solution repressed Mn toxicity symptoms, but had variable effects on the Mn content of leaves and roots. (Abstract retrieved from CAB Abstracts by CABI’s permission)