Foliar Application of Zn Phosphite and Zn EDTA in Soybean (Glycine max (L.) Merrill): In Vivo Investigations of Transport, Chemical Speciation, and Leaf Surface Changes

Abstract

Due to a zinc-deficient diet, about 800,000 children die each year worldwide. This aspect is amended by exploiting foliar fertilization, a useful alternative to improve crop yield and nutritional quality of food crops. The aim of this study was then to investigate the leaf uptake and transport of zinc by soybean (Glycine max (L) Merrill). Plant leaves were treated with Zn phosphite and Zn ethylenediamine tetra-acetic acid (EDTA) commercial formulations. X-ray spectroscopy (XRF and XANES) was exploited to trace nutrient movement in the petiolule and scanning electron microscopy (SEM) to evaluate the influence of leaf surface treatments. No radiation damage, in terms of elemental redistribution, was observed during the XRF and XANES measurements. As an alternative to radioisotopes, XRF allowed to detect the movement of Zn from both sources in the plant petiolule. Both fertilizers disintegrated leaf epicuticular wax crystals, yet accumulation of sediments in the vicinity of stomata was noted only for Zn phosphite. Absorption and redistribution of Zn were higher for plants that received Zn phosphite. Zinc supplied as Zn phosphite was transported in a form different from that of the pristine Zn phosphite, whereas Zn supplied as Zn EDTA was transported in its chelated form.

Effect of Counterions on the Foliar Absorption and Transport of Potassium in Soybeans [Glycine max (L.) Merrill]

“…As shown in this study, laboratory or benchtop X-ray fluorescence spectrometry emerges as a versatile alternative to radioisotopes, allowing us to trace the movement of ions within plants. A similar approach was previously employed to investigate the foliar absorption and transport of zinc and manganese by soybeans . The method can be extended to other plant species as shown by da Cruz et al, who monitored the root absorption of zinc by kidney beans ( Phaseolus vulgaris ).…”

“…Under certain experimental conditions, such as a relatively low X-ray flux density, μ-XRF is nondestructive, enabling the elemental determination in plants under in vivo conditions. 5,6,24 Hence, one can monitor the absorption and transport of nutrients in real time.…”

“…The X-ray fluorescence count rate of an element, frequently termed intensity, is directly proportional to its concentration; thus, this technique can determine both its presence and quantity. Under certain experimental conditions, such as a relatively low X-ray flux density, μ-XRF is nondestructive, enabling the elemental determination in plants under in vivo conditions. ,, Hence, one can monitor the absorption and transport of nutrients in real time.…”