The Magnesium Content and Potassium Magnesium Ratio of Tomato Leaves in Relation to Degree of Chlorosis

Publisher Website
Google Scholar
Abstract
The magnesium and potassium contents of the leaves of two tomato varieties have been studied for three seasons in a replicated nutritional trial in heated glasshouses. Magnesium sulphate was applied either to the soil or as a foliar spray, with untreated plots as controls, in combination with high and low levels of soil potassium. The samples analysed consisted of upper (5th from the top) leaves in the first season, 5th and 15th leaves in the second, and lower (15th) leaves in the third; the lower leaves proved more responsive to added magnesium. The treatments supplying magnesium increased the magnesium content of the foliage slightly in the first season and highly significantly in the subsequent years. Potassium had no effect on the magnesium content in the first season, but tended to depress it subsequently. The degree of chlorosis, assessed visually, was closely related to the magnesium content of the lower leaves of both varieties. The relationship was approximately linear for values up to about 0· 4% Mg, above which little chlorosis was ever found; the correlation coefficient for values up to 0·5% Mg in the leaves was –0·94 (P=0·001). Severe chlorosis occurred below 0·25%–0·30% Mg. The K{Mg ratios in the leaves were also significantly correlated (P=0· 001) with degree of chlorosis (r=+0·87 for values up to 0·5% Mg and +0·91 overall). Calculation of the multiple regression of chlorosis on % Mg and % K showed, however, that the regression coefficient of chlorosis on potassium content was not significant. The magnesium content of the lower leaves is thus regarded as a more satisfactory criterion of magnesium status than their K{Mg ratios.

This publication has 1 reference indexed in Scilit: