In situ analysis of foliar zinc absorption and short-distance movement in fresh and hydrated leaves of tomato and citrus using synchrotron-based X-ray fluorescence microscopy.
OBJECTIVE
Globally, zinc deficiency is one of the most important nutritional factors limiting crop yield and quality. Despite widespread use of foliar-applied zinc fertilizers, much remains unknown regarding the movement of zinc from the foliar surface into the vascular structure for translocation into other tissues and the key factors affecting this diffusion.


METHODS
Using synchrotron-based X-ray fluorescence microscopy (µ-XRF), absorption of foliar-applied zinc nitrate or zinc hydroxide nitrate was examined in fresh leaves of tomato (Solanum lycopersicum) and citrus (Citrus reticulatus).


RESULTS
The foliar absorption of zinc increased concentrations in the underlying tissues by up to 600-fold in tomato but only up to 5-fold in citrus. The magnitude of this absorption was influenced by the form of zinc applied, the zinc status of the treated leaf and the leaf surface to which it was applied (abaxial or adaxial). Once the zinc had moved through the leaf surface it appeared to bind strongly, with limited further redistribution. Regardless of this, in these underlying tissues zinc moved into the lower-order veins, with concentrations 2- to 10-fold higher than in the adjacent tissues. However, even once in higher-order veins, the movement of zinc was still comparatively limited, with concentrations decreasing to levels similar to the background within 1-10 mm.


CONCLUSIONS
The results advance our understanding of the factors that influence the efficacy of foliar zinc fertilizers and demonstrate the merits of an innovative methodology for studying foliar zinc translocation mechanisms.
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Yumei
Y
Du
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Peter M
PM
Kopittke
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Barry N
BN
Noller
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Simon A
SA
James
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Hugh H
HH
Harris
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Zhi Ping
ZP
Xu
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
Peng
P
Li
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia.
David R
DR
Mulligan
Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, Queensland 4072, Australia, School of Agriculture and Food Sciences, The University of Queensland, St Lucia, Queensland 4072, Australia, Australian Synchrotron, Clayton, Victoria 3168, Australia, School of Chemistry and Physics, University of Adelaide, South Australia 5005, Australia, School of Chemical Engineering, The University of Queensland, St Lucia, Queensland 4072, Australia and ARC Centre of Excellence for Functional Nanomaterials, The University of Queensland, St Lucia, Queensland 4072, Australia l.huang@uq.edu.au.
Longbin
L
Huang
D000367:Age Factors; D002957:Citrus / Q000378:metabolism*; D004058:Diffusion; D005308:Fertilizers; D018551:Solanum lycopersicum / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D018515:Plant Leaves / Q000378:metabolism; D013045:Species Specificity; D017356:Synchrotrons; D015032:Zinc / Q000378:metabolism*
D005308:Fertilizers; D015032:Zinc
Citrus reticulatus; Nutrient absorption; Solanum lycopersicum; X-ray fluorescence microscopy; XRF; Zn movement; crop nutrition; foliar zinc application; short-distance nutrient transport; tomato; veins