Resumo: O objetivo deste trabalho foi avaliar o potencial de translocação de solutos entre colmos de trigo (Triticum aestivum), por meio da aplicação dos herbicidas sistêmicos cletodim e glifosato. Os experimentos foram realizados em cultivo protegido, com cultivares contrastantes quanto ao potencial de perfilhamento, durante o inverno de 2017 e 2018, no Sul do Brazil. O cletodim foi aplicado em colmos isolados, para se avaliar o potencial de translocação a partir dos três primeiros perfilhos. A translocação foi avaliada, por meio dos parâmetros produtivos, em espigas de colmos não tratados com cletodim. O glifosato foi utilizado para avaliar o potencial de translocação a partir dos perfilhos tardios. A translocação foi avaliada por meio da assimilação de carbono, em colmos sem o tratamento com glifosato. Quando aplicado nos perfilhos primários isolados, o cletodim reduziu os parâmetros produtivos apenas em colmos tratados com o herbicida, o que mostra o direcionamento de assimilados para o dreno principal, em detrimento de outros órgãos. Houve decréscimo da assimilação de carbono em colmos sem o tratamento com glifosato, no estádio de primeiro nó visível. O glifosato aplicado a perfilhos tardios, na antese, reduziu ainda mais a assimilação de carbono em colmos primários não tratados da cultivar de trigo BRS Parrudo (baixo perfilhamento). Perfilhos tardios bem desenvolvidos apresentam maior potencial de translocação de solutos para o restante da planta do que os pouco desenvolvidos.

Abstract: The objective of this work was to evaluate the potential of solute translocation among stems of wheat (Triticum aestivum), by the application of the systemic herbicides clethodim and glyphosate. The experiments were carried out in greenhouse conditions, using wheat cultivars with contrasting potential for tillering, during the winter of 2017 and 2018 in Southern Brazil. Clethodim was applied on isolated stems, to evaluate the potential translocation of solutes from the first three tillers. Translocation was evaluated by the yield parameters on stem ears not treated with clethodim. Glyphosate was used to evaluate the potential translocation of solutes from late tillers. Translocation was evaluated by the assimilation of carbon in stems without the glyphosate treatment. When applied on isolated primary tillers, clethodim reduced yield parameters only in treated stems, which shows that the assimilates were targeting the main sink, in detriment of the other organs. There was a decrease in net carbon assimilation in stems without the glyphosate treatment at the first visible node stage. Glyphosate applied on late tillers, at anthesis, reduced even more net carbon assimilation in nontreated stems of the primary tillers of the BRS Parrudo wheat cultivar (low tillering). Well-developed late tillers show higher potential of solute translocation to the whole plant than the poor-developed ones.

ABSTRACT Although source–sink relationships in wheat are well studied, the performance of tillers as transient sinks is still unclear, especially under stress conditions. Thus, this work aimed to study the yield relationships of wheat stems in contrasting genotypes as affected by tiller treatment under stress conditions. Two experiments were conducted under greenhouse conditions using BRS Guamirim (high tillering) and BRS Parrudo (low tillering) wheat cultivars. Four tillering treatments were applied on late tillers in the first growing season (2016) and three in the second (2017): (i) free-tillering, (ii) detillering, (iii) physical suppression (only in the first season) and (iv) “spikes removal”. The main stem and the first four emitted tillers were considered as primary tillers. Plants were submitted to drought (2016) and defoliation stress (2017) at preanthesis. Intraspecific competition among tillers increased under drought stress conditions and decreased the plant performance. Nonproductive late tillers do not improve the performance of primary tillers of wheat plants under drought stress, mainly in high-tillering cultivars. The reduction on the thousand grain weight of only ‘Parrudo’ detillered plants indicates that assimilate remobilization from late tillers to primary tillers and main stem seems to be more effective in low-tillering cultivars.

ABSTRACT Despite being an important crop option for Brazilian agriculture, canola has some characteristics that may limit its insertion in some cropping systems, such as its allelopathic effects. Thus, the present work aimed to study the effect of canola crop residues on the seed germination, growth and grain yield of white oat and wheat plants. In laboratory conditions, white oat (Milton) and wheat (Tbio Pioneiro) seeds were germinated in the presence of aqueous extracts of (i) aboveground part, (ii) root system, (iii) whole plant and (iv) twice the concentration of the whole plant extract, besides a control. In green house conditions, the same oat and wheat cultivars were grown until harvest, on soil mixed with fresh canola crop residues (whole plant residues, aboveground residues and root residues) and a control. Aqueous extract of the whole canola plant reduced the germination and increased abnormal seedlings of white oat and wheat, mainly in high concentration. For soil crop, the presence of canola residues did not affect the white oat emergence, growth and grain yield. For wheat, plant emergence was lower in the presence of canola residues, but growth and yield were not affected.