American Journal of Plant Sciences, 2017, 8, 2795-2810 http://www.scirp.org/journal/ajps ISSN Online: 2158-2750 ISSN Print: 2158-2742 DOI: 10.4236/ajps.2017.811189 Oct. 26, 2017 2795 American Journal of Plant Sciences Grain Yield Differences of Soybean Cultivars Due to Solar Radiation Interception Mariele Müller 1 , Miroslava Rakocevic 2 , Andréia Caverzan 1 , Geraldo Chavarria 1* 1 Faculty of Agronomy and Veterinary Medicine, Agronomy Post-Graduate Program, University of Passo Fundo, Passo Fundo, Brazil 2 Embrapa Agriculture Informatics, Campinas, Brazil Abstract Soybean [Glycine max (L.) Merr.] growth rate and grain yield are modified by the interception and solar radiation use efficiency. Thus, it is desirable that the most of plant photosynthetic structures intercepting solar radiation in order to have increment in carbon fixation and reflection on growth and yield. The goal of this study was to assess if soybean cultivars differ in grain yield in rela- tion to solar radiation interception. Four soybean cultivars were evaluated at stages V6, V9, R2, R4, R6 and R8. To determine the photosynthetically active radiation interception by the canopy, the plants were divided into two parts (upper and lower strata). For grain yield components, the plants were divided into three parts (upper, middle and lower thirds). Of the photosynthetically active radiation intercepted by the vegetative canopy at the reproductive stag- es, the maximum observed intercept was 5.2% in the lower stratum of the plants. The number of infertile nodes increased in the lower third of plants due to low interception of solar radiation in this plant region. Thus, the soy- bean cultivars more efficient in intercepting photosynthetically active radia- tion inside the vegetative canopy showed higher grain yields. Keywords Glycine Max, Leaf Area Index, Efficiency of Solar Radiation Interception, Extinction Coefficient, Solar Radiation Use Efficiency 1. Introduction Plant growth depends on carbon assimilation, which is directly related to inter- cepted photosynthetically active radiation (IPAR). Part of photosynthetically ac- tive radiation (PAR) is absorbed and used in photosynthesis, and the rest is lost How to cite this paper: Müller, M., Rako- cevic, M., Caverzan, A. and Chavarria, G. (2017) Grain Yield Differences of Soybean Cultivars Due to Solar Radiation Intercep- tion. American Journal of Plant Sciences, 8, 2795-2810. https://doi.org/10.4236/ajps.2017.811189 Received: September 2, 2017 Accepted: October 23, 2017 Published: October 26, 2017 Copyright © 2017 by authors and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access