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Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings

The mature inflorescence of sunflowers (Helianthus annuus) orients eastward after its anthesis (the flowering period, especially the maturing of the stamens), from which point it no longer tracks the Sun. Although several hypothetical explanations have been proposed for the ecological functions of t...

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Autores principales: Horváth, Gábor, Slíz-Balogh, Judit, Horváth, Ákos, Egri, Ádám, Virágh, Balázs, Horváth, Dániel, Jánosi, Imre M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Nature Publishing Group UK 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725789/
https://www.ncbi.nlm.nih.gov/pubmed/33299003
http://dx.doi.org/10.1038/s41598-020-78243-z
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author Horváth, Gábor
Slíz-Balogh, Judit
Horváth, Ákos
Egri, Ádám
Virágh, Balázs
Horváth, Dániel
Jánosi, Imre M.
author_facet Horváth, Gábor
Slíz-Balogh, Judit
Horváth, Ákos
Egri, Ádám
Virágh, Balázs
Horváth, Dániel
Jánosi, Imre M.
author_sort Horváth, Gábor
collection PubMed
description The mature inflorescence of sunflowers (Helianthus annuus) orients eastward after its anthesis (the flowering period, especially the maturing of the stamens), from which point it no longer tracks the Sun. Although several hypothetical explanations have been proposed for the ecological functions of this east facing, none have been tested. Here we propose an atmospheric-optical explanation. Using (i) astronomical data of the celestial motion of the Sun, (ii) meteorological data of diurnal cloudiness for Boone County located in the region from which domesticated sunflowers originate, (iii) time-dependent elevation angle of mature sunflower heads, and (iv) absorption spectra of the inflorescence and the back of heads, we computed the light energy absorbed separately by the inflorescence and the back between anthesis and senescence. We found that the inflorescences facing east absorb the maximum radiation, being advantageous for seed production and maturation, furthermore west facing would be more advantageous than south facing. The reason for these is that afternoons are cloudier than mornings in the cultivation areas of sunflowers. Since the photosynthesizing green back of mature heads absorbs maximal energy when the inflorescence faces west, maximizing the energy absorbed by the back cannot explain the east facing of inflorescences. The same results were obtained for central Italy and Hungary, where mornings are also less cloudy than afternoons. In contrast, in south Sweden, where mornings are cloudier than afternoons, west-facing mature inflorescences would absorb the maximum light energy. We suggest that the domesticated Helianthus annuus developed an easterly final orientation of its mature inflorescence, because it evolved in a region with cloudier afternoons.
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spelling pubmed-77257892020-12-14 Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings Horváth, Gábor Slíz-Balogh, Judit Horváth, Ákos Egri, Ádám Virágh, Balázs Horváth, Dániel Jánosi, Imre M. Sci Rep Article The mature inflorescence of sunflowers (Helianthus annuus) orients eastward after its anthesis (the flowering period, especially the maturing of the stamens), from which point it no longer tracks the Sun. Although several hypothetical explanations have been proposed for the ecological functions of this east facing, none have been tested. Here we propose an atmospheric-optical explanation. Using (i) astronomical data of the celestial motion of the Sun, (ii) meteorological data of diurnal cloudiness for Boone County located in the region from which domesticated sunflowers originate, (iii) time-dependent elevation angle of mature sunflower heads, and (iv) absorption spectra of the inflorescence and the back of heads, we computed the light energy absorbed separately by the inflorescence and the back between anthesis and senescence. We found that the inflorescences facing east absorb the maximum radiation, being advantageous for seed production and maturation, furthermore west facing would be more advantageous than south facing. The reason for these is that afternoons are cloudier than mornings in the cultivation areas of sunflowers. Since the photosynthesizing green back of mature heads absorbs maximal energy when the inflorescence faces west, maximizing the energy absorbed by the back cannot explain the east facing of inflorescences. The same results were obtained for central Italy and Hungary, where mornings are also less cloudy than afternoons. In contrast, in south Sweden, where mornings are cloudier than afternoons, west-facing mature inflorescences would absorb the maximum light energy. We suggest that the domesticated Helianthus annuus developed an easterly final orientation of its mature inflorescence, because it evolved in a region with cloudier afternoons. Nature Publishing Group UK 2020-12-09 /pmc/articles/PMC7725789/ /pubmed/33299003 http://dx.doi.org/10.1038/s41598-020-78243-z Text en © The Author(s) 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
spellingShingle Article
Horváth, Gábor
Slíz-Balogh, Judit
Horváth, Ákos
Egri, Ádám
Virágh, Balázs
Horváth, Dániel
Jánosi, Imre M.
Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title_full Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title_fullStr Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title_full_unstemmed Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title_short Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
title_sort sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7725789/
https://www.ncbi.nlm.nih.gov/pubmed/33299003
http://dx.doi.org/10.1038/s41598-020-78243-z
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