Manganese toxicity and marginal chlorosis of lettuce

Summary Romaine lettuce plants were grown in 15-liter tanks containing one-fifth strength Hoagland's solution over a range of Mn concentrations from zero to 10 ppm. This covered a span of Mn from deficiency to toxicity. Maximum yields were obtained at 0.1 and 0.5 ppm Mn supplied in the nutrient solution. A marginal chlorosis appeared at the highest Mn rates and was more pronounced in the older leaves. The plants were divided into young and old leaves and roots. The yellow borders of the old leaves were separated for analysis from the interior green tissues. The Mn content of the chlorotic borders averaged three times higher than that in the interior green tissues and reached a maximum of 5430 ppm Mn as opposed to 1940 ppm. The Fe content of the chlorotic bands was more than twice as high as that found in the green parts of the blades. The maximum content of Mn found in the roots was 3660 ppm. re]19720118