MANGANESE DEFICIENCY AND TOXICITY IN GREENHOUSE TOMATOES

Abstract

Symptoms of manganese deficiency and toxicity on greenhouse tomatoes (Lycopersicon esculentum Mill.), produced experimentally in sand culture, were related to Mn content determined in tissues of leaves, petioles, stems, suckers, roots, and fruits. The highest concentration of Mn found in tissue showing deficiency symptoms was 25 ppm, although this level of Mn also was found in some healthy tissues. Severe deficiency was associated with all tissues, except fruit, that contained 20 ppm Mn or less. An exact threshold value for the onset of Mn toxicity was difficult to define, but probably occurred between 450 and 500 ppm for young top leaves and between 900 and 1,000 ppm for older lower leaves. The tomato plant will tolerate a wide range of Mn levels in apparently healthy tissue.