Department of Agricultural Sciences, University of Naples Federico II, via Università 100, 80055, Portici (NA), Italy.
CNR-Istituto Nazionale di Ottica, via Campi Flegrei 34 (comprensorio A. Olivetti), 80078, Pozzuoli (NA), Italy.
New Phytol. 2019 Oct;224(2):987-993. doi: 10.1111/nph.16084. Epub 2019 Sep 4.
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.
花中糖浓度是几个不同应用领域所需的评估指标。广泛应用的分析方法是用微毛细管提取花蜜并用光折射仪测量糖浓度，但当花蜜分泌量少时，微毛细管无法提取，该方法就不可靠了。在这种情况下采用的辅助方法具有破坏性，比较复杂，并且通常提供的结果精度和准确性要低得多。光纤的微观尺寸、低成本和生物相容性被利用来以最小的侵入性将光直接输送到花内，并在不提取花蜜的情况下即时测量其折射特性。在使用两种已知的花蜜植物对新老方法进行比较后，该新方法在 Primula palinuri 上得到了验证，该植物的花蜜无法用微毛细管提取。光纤探头能够测量 P. palinuri 花朵中的花蜜折光指数，从而可以突出显示以前未检测到的单花长花期内糖浓度的显著趋势。长花柱花和短花柱花的花蜜浓度变化相似。光纤折射计是光折射计分析的一种进步。进一步将实验室设备定制为便携式设备将促进其应用。
