title: The use of laser light to enhance the uptake of foliar-applied substances into citrus (Citrus sinensis) leaves.
abstract: OBJECTIVE
  Uptake of foliar-applied substances across the leaf cuticle is central to world food production as well as for physiological investigations into phloem structure and function. Yet, despite the presence of stomata, foliar application as a delivery system can be extremely inefficient due to the low permeability of leaf surfaces to polar compounds.
  
  
  METHODS
  Using laser light to generate microscopic perforations in the leaf cuticle, we tested the penetration of several substances into the leaf, their uptake into the phloem, and their subsequent movement through the phloem tissue. Substances varied in their size, charge, and Stokes radius.
  
  
  RESULTS
  The phloem-mobile compounds 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG), lysine, Biocillin, adenosine triphosphate (ATP), trehalose, carboxyfluorescein-SE, and poly(amidomine) (PAMAM) dendrimer G-4 nanoparticles (4.5 nm in size) showed a high degree of mobility and were able to penetrate and be transported in the phloem.
  
  
  CONCLUSIONS
  Our investigation demonstrated the effectiveness of laser light technology in enhancing the penetration of foliar-applied substances into citrus leaves. The technology is also applicable to the study of phloem mobility of substances by providing a less invasive, highly repeatable, and more quantifiable delivery method. The implied superficial lesions to the leaf can be mitigated by applying a waxy coating.
authors.affiliation: Citrus Research and Education Center (CREC), University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850 USA.
authors.forename: Ed
authors.initials: E
authors.lastname: Etxeberria
authors.affiliation: Citrus Research and Education Center (CREC), University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850 USA.
authors.forename: Pedro
authors.initials: P
authors.lastname: Gonzalez
authors.affiliation: Citrus Research and Education Center (CREC), University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850 USA; Yale School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511 USA.
authors.forename: Ana
authors.initials: A
authors.lastname: Fanton Borges
authors.affiliation: Citrus Research and Education Center (CREC), University of Florida, 700 Experiment Station Road, Lake Alfred, Florida 33850 USA; Yale School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511 USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Brodersen
keywords: Citrus; foliar sprays; foliar uptake; laser light; phloem diseases; phloem movement
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