Fiber-optic refractometer for in vivo sugar concentration measurements of low-nectar-producing flowers

Year: 2019

Authors: Aronne G., Malara P.

Autors Affiliation: Univ Naples Federico II, Dept Agr Sci, Via Univ 100, I-80055 Portici, NA, Italy; CNR, Ist Nazl Ott, Via Campi Flegrei 34 Comprensorio A Olivetti, I-80078 Pozzuoli, NA, Italy

Abstract: Sugar concentration in floral nectars is an assessment required in several diverse fields of application. The widely used analysis, consisting of nectar extraction with a microcapillary and sugar concentration measurement with a light refractometer, is not reliable when the nectar is secreted in small quantities, unextractable with a microcapillary. Ancillary methods adopted in such cases are destructive, rather complicated and often provide much less precise and accurate results. The microscopic-size, low cost and biocompatibility of optical fibers were exploited to deliver light directly inside the flower with minimal invasiveness and measure instantaneously the refractometric properties of the nectar without extracting it. After comparing the new and old methods using two known nectariferous species, the new approach was validated on Primula palinuri, whose nectar is unextractable with microcapillaries. The fiber-optic probe was able to measure the nectar refractive index in P. palinuri flowers making it possible to highlight a previously undetected significant trend of the sugar concentration throughout the long anthesis of the single flowers. Changes in nectar concentrations are similar in both longistylous and brevistylous flowers. The fiber-optic refractometer is an advancement of light refractometer analysis. Further customization of the laboratory set-up into portable equipment will boost applications.


Volume: 224 (2)      Pages from: 987  to: 993

KeyWords: low-nectar-producing flowers; nectar; nectar sugar concentration; optical fibers; Primula palinuri; refractometer
DOI: 10.1111/nph.16084

Citations: 9
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