02436naa a2200361 a 450000100080000000500110000800800410001902400410006010000180010124001090011924501050022826000090033352013030034265000150164565000200166065000210168065000130170165000230171465000160173765000160175365000090176965300120177865300200179065300210181065300270183165300210185865300220187970000170190170000230191870000220194170000210196377300900198418624652017-10-31       2010    bl uuuu     u00u1 u    #d7 a10.1590/S0100-204X20100007000052DOI1 aRAKOCEVIC, M.  aRespostas heliotrópicas de cultivares de soja em três estádios fenológicos e dois regimes hídricos.  aHeliotropic responses of soybean cultivars at three phenological stages and under two water regimes.  c2010  aThe 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.  aIrrigation  aLeaf area index  aPlant physiology  aSoybeans  aFisiologia vegetal  aGlycine Max  aIrrigação  aSoja  aCosseno  aDiaheliotropism  aDiaheliotropismo  aIndice de área foliar  aParaheliotropism  aParaheliotropismo1 aNEUMAIER, N.1 aOLIVEIRA, G. M. de1 aNEPOMUCENO, A. L.1 aFARIAS, J. R. B.  tPesquisa Agropecuária Brasileira, Brasília, DFgv. 45, n. 7, p. 661-670, jul. 2010.