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A combination of artificial intelligence with reflectance spectroscopy was tested, as a non-invasive method, for the automatic classification of plant drought stress. Arabidopsis thaliana plants (ecotype Col-0) were subjected to different levels of slowly imposed dehydration (S0, control; S1, moderate stress; S2, severe stress). The reflectance spectra of fully expanded leaves were recorded with an Ocean Optics USB4000 spectrometer and the soil water content (SWC, %) of each pot was determined. The entire data set of the reflectance spectra (intensity vs. wavelength) was given to different machine learning (ML) algorithms, namely decision trees, random forests and extreme gradient boosting. The performance of different methods in classifying the plants in one of the three drought stress classes (S0, S1 and S2) was measured and compared. All algorithms produced very high evaluation scores (F1 &gt; 90%) and agree on the features with the highest discriminative power (reflectance at ~670 nm). Random forests was the best performing method and the most robust to random sampling of training data, with an average F1-score of 0.96 \u00b1 0.05. This classification method is a promising tool to detect plant physiological responses to drought using high-throughput pipelines.<\/jats:p>","DOI":"10.3390\/app11146392","type":"journal-article","created":{"date-parts":[[2021,7,12]],"date-time":"2021-07-12T00:23:36Z","timestamp":1626049416000},"page":"6392","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":26,"title":["Comparing Machine Learning Methods for Classifying Plant Drought Stress from Leaf Reflectance Spectra in Arabidopsis thaliana"],"prefix":"10.3390","volume":"11","author":[{"given":"Ana","family":"Barradas","sequence":"first","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2692-7691","authenticated-orcid":false,"given":"Pedro M.P.","family":"Correia","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Departamento de Biologia Vegetal, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sara","family":"Silva","sequence":"additional","affiliation":[{"name":"LASIGE, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3813-1009","authenticated-orcid":false,"given":"Pedro","family":"Mariano","sequence":"additional","affiliation":[{"name":"Centro de Ci\u00eancias e Tecnologias Nucleares, Instituto Superior T\u00e9cnico, 2695-066 Bobadela, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Margarida Calejo","family":"Pires","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3495-2195","authenticated-orcid":false,"given":"Ana Rita","family":"Matos","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Departamento de Biologia Vegetal, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4904-7470","authenticated-orcid":false,"given":"Anabela Bernardes","family":"da Silva","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Departamento de Biologia Vegetal, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5583-2715","authenticated-orcid":false,"given":"Jorge","family":"Marques da Silva","sequence":"additional","affiliation":[{"name":"BioISI\u2014Biosystems and Integrative Sciences Institute, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"},{"name":"Departamento de Biologia Vegetal, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,7,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"812","DOI":"10.1126\/science.1185383","article-title":"Food security: The challenge of feeding 9 billion people","volume":"327","author":"Godfray","year":"2010","journal-title":"Science"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"168","DOI":"10.1016\/j.pbi.2019.11.004","article-title":"Innovations in plant genetics adapting agriculture to climate change","volume":"56","author":"Henry","year":"2019","journal-title":"Curr. 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