Effects of individual and combined metal foliar fertilisers on iron- and manganese-deficient Solanum lycopersicum plants

Using Fe- and Mn-deficient Solanum lycopersicum plants, we investigated the effects of Fe and Mn foliar fertilisers, either individually or combined, on plant biomass, leaf chlorophyll and metal micronutrient levels in leaves and roots. Plants were grown in hydroponics with different combinations of 0 or 45 mu M Fe and 0 or 4.6 mu M Mn. Foliar fertiliser formulations (9 mM FeSO4 and/or 3 mM MnSO4, supplemented with a surfactant) were applied in three consecutive doses. Fertilisation was applied to the first three leaf levels, while upper leaf levels were left untreated. Iron and Mn deficiency led to characteristic symptoms. Foliar treatments increased concentrations of Fe and Mn, biomass and chlorophyll in treated leaves, although re-greening was incomplete. Approximately 11-12 % of the Fe increase was in roots (likely mediated via phloem transport), but no Fe increase occurred in untreated leaves. Regarding Mn, a 2 % increase occurred in untreated leaves, but no increase occurred in roots. Iron fertilisation was effective not only in leaves treated with the fertiliser but also in roots, whereas Mn fertilisation had major effects on treated leaves and minor effects on untreated ones. The combined application of Fe + Mn was not detrimental to Fe- or Mn-deficient plants.