Heliotropic responses of soybean cultivars at three phenological stages and under two water regimes

Abstract

-The objectives of this work were to determine the heliotropic movements of the upper trifoliates for two soybean cultivars, BR 16 and Embrapa 48, during a daily cycle, in three phenological stages and two water regimes, and to estimate the impact of irrigation and daily leaflet movements on agronomic characteristics and grain yield. Heliotropic movements were studied in three phenological stages: V4-V6, V7-V10, and R5 in irrigated and non-irrigated plots. For each stage, the leaflet elevation and azimuth were measured hourly. Under a low (V4-V6 stage) and mid (V7-V10 stage) leaf area index (LAI) the diaheliotropism was slightly more frequent and intensive in non-irrigated than in irrigated plants, only at early morning and late afternoon hours. At R5 stage (high LAI) the paraheliotropism of superior trifoliates was predominant and more intensive in non-irrigated plants. The heliotropic movements are correlated to carbon gain, but not to environment (light intensity or temperature), for measurements at 11h. 'Embrapa 48' expresses greater paraheliotropism than 'BR 16' at high LAI, while 'BR 16' displays lower heliotropic plasticity under irrigation. In spite of significant heliotropic differences, genotype and water availability treatments did not influence the final grain yield.Index terms: Glycine max, diaheliotropism, irrigation, leaf area index, paraheliotropism. Respostas heliotrópicas de cultivares de soja em três estádios fenológicos e dois regimes hídricosResumo -Os objetivos deste trabalho foram determinar o movimento heliotrópico dos trifólios superiores de duas cultivares de soja, BR 16 e Embrapa 48, durante o dia, em três estádios fenológicos e em dois regimes hídricos e determinar o impacto da irrigação e do movimento foliar diário nas características agronômicas e na produção de grãos. Movimentos heliotrópicos foram determinados a cada hora, em três estádios fenológicos: V4-V6, V7-V10 e R5, em parcelas irrigadas e não irrigadas. Para cada estágio, a elevação do folíolo e o azimute foram medidos por hora. Em índices de área foliar (IAF) baixo e médio (V4-V6 e V7-V10), o diaheliotropismo foi levemente mais intenso e frequente nas plantas sem irrigação do que nas irrigadas, e somente nas primeiras horas matinais e últimas horas da tarde. Em R5 (alto IAF), o paraheliotropismo dos trifólios superiores foi predominante e mais intenso em plantas não irrigadas. Os movimentos heliotrópicos se correlacionaram com o ganho de carbono mas não com o ambiente (intensidade de luz ou temperatura), para medidas às 11 horas. 'Embrapa 48' apresenta maior paraheliotropismo do que 'BR 16', em plantas com alto IAF enquanto 'BR 16' apresenta menor plasticidade nas respostas heliotrópicas nas parcelas irrigadas. Apesar de diferenças no heliotropismo, o genótipo e disponibilidade de água não influenciaram a produção de grãos.Termos para indexação: Glycine max, cosseno, diaheliotropismo, irrigação, índice de área foliar, paraheliotropismo.

Architectural Characteristics and Heliotropism May Improve Spray Droplet Deposition in the Middle and Low Canopy Layers in Soybean

“…The frequency of diaheliotropic movements is also severely reduced during the reproductive stage (R5) compared with the vegetative stages (V7-V10) in 'Embrapa 48' and 'BR 16', widely used Brazilian cultivars, suggesting that soybean tends to position its leaflets parallel to the sun rays in the final developmental stages (Rakocevic et al, 2010). The frequency of diaheliotropic movements is also severely reduced during the reproductive stage (R5) compared with the vegetative stages (V7-V10) in 'Embrapa 48' and 'BR 16', widely used Brazilian cultivars, suggesting that soybean tends to position its leaflets parallel to the sun rays in the final developmental stages (Rakocevic et al, 2010).…”

“…Digital photography was used to estimate leaflet elevation and azimuth (Rakocevic et al, 2010). Digital photography was used to estimate leaflet elevation and azimuth (Rakocevic et al, 2010).…”

Soybean Architecture Plants: From Solar Radiation Interception to Crop Protection

“…Paraheliotropism is a movement maintaining the leaf blades parallel to the solar rays and reducing the effects of hydric stress [36], photoinhibition [37] and high leaf temperature [38]. Genotypes respond differently to heliotropism and besides that, those responses differ during the cultivation cycle and under stressing conditions [39].…”

Variation in leaf orientation and its related traits in sunflower (Helianthus annuus L.) breeding populations under high temperature

“…(Charzewska, 2006). Rakocevic et al (2010) showed in soybean that paraheliotropism was predominant under stress environment as compared to diaheliotropism while cultivar differences were also observed for these movements. Paraheliotropism movements allow lamina temperature to remain close to the thermal optimum of photosynthesis and other leaf gas exchange activities (Bielenberg et al, 2003).…”

“…A species may show both types of movements as directed by the environment (high leaf temperature, soil and water potential of plant, photosynthetic photon flux density, PPFD) and specific genotypes (Charzewska, 2006;Rakocevic et al, 2010). In sunflower (Helinathus annuus L.), pulvinal tissues around the stem induces heliotropic movements in response to the external environment * Corresponding author.…”