{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T08:18:46Z","timestamp":1768551526181,"version":"3.49.0"},"reference-count":48,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2019,3,5]],"date-time":"2019-03-05T00:00:00Z","timestamp":1551744000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002341","name":"Academy of Finland","doi-asserted-by":"publisher","award":["293443, 88039"],"award-info":[{"award-number":["293443, 88039"]}],"id":[{"id":"10.13039\/501100002341","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Finnish Centre of Excellence","award":["307331"],"award-info":[{"award-number":["307331"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>Successful measurements of chlorophyll fluorescence (ChlF) spectral properties (typically in the wavelength range of 650\u2013850 nm) across plant species, environmental conditions, and stress levels are a first step towards establishing a quantitative link between solar-induced chlorophyll fluorescence (SIF), which can only be measured at discrete ChlF spectral bands, and photosynthetic functionality. Despite its importance and significance, the various methodologies for the estimation of leaf-level ChlF spectral properties have not yet been compared, especially when applied to leaves with complex morphology, such as needles. Here we present, to the best of our knowledge, a first comparison of protocols for measuring leaf-level ChlF spectra: a custom-made system designed to measure ChlF spectra at ambient and 77 K temperatures (optical chamber, OC), the widely used FluoWat leaf clip (FW), and an integrating sphere setup (IS). We test the three methods under low-light conditions, across two broadleaf species and one needle-like species. For the conifer, we characterize the effect of needle arrangements: one needle, three needles, and needle mats with as little gap fraction as technically possible. We also introduce a simple baseline correction method to account for non-fluorescence-related contributions to spectral measurements. Baseline correction was found especially useful in recovering the spectra nearby the filter cut-off. Results show that the shape of the leaf-level ChlF spectra remained largely unaffected by the measurement methodology and geometry in OC and FW methods. Substantially smaller red\/far-red ratios were observed in the IS method. The comparison of needle arrangements indicated that needle mats could be a practical solution to investigate temporal changes in ChlF spectra of needle-like leaves as they produced more reproducible results and higher signals.<\/jats:p>","DOI":"10.3390\/rs11050532","type":"journal-article","created":{"date-parts":[[2019,3,5]],"date-time":"2019-03-05T11:19:50Z","timestamp":1551784790000},"page":"532","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Leaf-Level Spectral Fluorescence Measurements: Comparing Methodologies for Broadleaves and Needles"],"prefix":"10.3390","volume":"11","author":[{"given":"Paulina A.","family":"Rajewicz","sequence":"first","affiliation":[{"name":"Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research\/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, 00014 Helsinki, Finland"}]},{"given":"Jon","family":"Atherton","sequence":"additional","affiliation":[{"name":"Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research\/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, 00014 Helsinki, Finland"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8221-5739","authenticated-orcid":false,"given":"Luis","family":"Alonso","sequence":"additional","affiliation":[{"name":"Image Processing Laboratory (IPL), University of Valencia, Paterna, 46980 Val\u00e8ncia, Spain"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1357-9982","authenticated-orcid":false,"given":"Albert","family":"Porcar-Castell","sequence":"additional","affiliation":[{"name":"Optics of Photosynthesis Laboratory, Institute for Atmospheric and Earth System Research\/Forest Sciences, Faculty of Agriculture and Forestry, University of Helsinki, 00014 Helsinki, Finland"}]}],"member":"1968","published-online":{"date-parts":[[2019,3,5]]},"reference":[{"key":"ref_1","first-page":"34","article-title":"Mapping Photosynthesis from Space\u2014A New Vegetation-Fluorescence Technique","volume":"116","author":"Davidson","year":"2003","journal-title":"Eur. 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