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

Abstract 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 funct...

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Autores principales:	Gábor Horváth, Judit Slíz-Balogh, Ákos Horváth, Ádám Egri, Balázs Virágh, Dániel Horváth, Imre M. Jánosi
Formato:	article
Lenguaje:	EN
Publicado:	Nature Portfolio 2020
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/c3ed4b5f9dde41aea88ab32d3acf0155
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spelling	oai:doaj.org-article:c3ed4b5f9dde41aea88ab32d3acf01552021-12-02T16:18:05ZSunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings10.1038/s41598-020-78243-z2045-2322https://doaj.org/article/c3ed4b5f9dde41aea88ab32d3acf01552020-12-01T00:00:00Zhttps://doi.org/10.1038/s41598-020-78243-zhttps://doaj.org/toc/2045-2322Abstract 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.Gábor HorváthJudit Slíz-BaloghÁkos HorváthÁdám EgriBalázs VirághDániel HorváthImre M. JánosiNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 10, Iss 1, Pp 1-15 (2020)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Gábor Horváth Judit Slíz-Balogh Ákos Horváth Ádám Egri Balázs Virágh Dániel Horváth Imre M. Jánosi Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
description	Abstract 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.
format	article
author	Gábor Horváth Judit Slíz-Balogh Ákos Horváth Ádám Egri Balázs Virágh Dániel Horváth Imre M. Jánosi
author_facet	Gábor Horváth Judit Slíz-Balogh Ákos Horváth Ádám Egri Balázs Virágh Dániel Horváth Imre M. Jánosi
author_sort	Gábor Horváth
title	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_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_sort	sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings
publisher	Nature Portfolio
publishDate	2020
url	https://doaj.org/article/c3ed4b5f9dde41aea88ab32d3acf0155
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Sunflower inflorescences absorb maximum light energy if they face east and afternoons are cloudier than mornings

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