Interactive Effects of Grafting and Manganese Supply on Growth, Yield, and Nutrient Uptake by Tomato

Abstract

Tomato (Solanum lycopersicum L. cv. Belladona F1) plants were either self-grafted or grafted onto the rootstock ‘He-Man’ and grown in recirculating nutrient solution with low, standard, or high manganese (Mn) concentrations (2, 15, and 100 μM, respectively). The concentrations of all nutrients except Mn were identical in all treatments. The objectives of the experiment were to test whether grafted tomato plants have a higher or lower ability to withstand deficient or toxic levels of Mn in the root zone and to study the effects of grafting on nutrient uptake and translocation to the aerial organs. Both excessive and insufficient Mn concentrations in the root zone significantly reduced the number of fruit per plant, whereas mean fruit weight was unaffected by external Mn concentrations ranging from ≈1 to 100 μM. The excessive external Mn concentration caused the leaf Mn concentration to increase beyond the critically high level at the expense of leaf and root iron and zinc concentrations but without significant differences between the grafting treatments. The fruit yield of plants grafted onto ‘He-Man’ was significantly lower than that of self-grafted plants when the Mn concentration in the root zone was excessively high. This response might be associated with the lower translocation of magnesium (Mg) to the leaves of plants grafted onto ‘He-Man’ in comparison with the self-grafted plants, resulting in lower Mg/Mn ratios in the leaves. Grafting onto ‘He-Man’ also restricted the leaf and root iron and copper concentrations but enhanced those of potassium. Overall, tomato cv. Belladona proved to be more tolerant to excess Mn than to Mn deficiency in terms of vegetative growth and fruit yield.