Photosynthetic characteristics of hybrid and conventional rice plants as a function of plant competition

Abstract

-The objective of this work was to evaluate the characteristics related to the photosynthetic ability of hybrid and inbred rice varieties, as a way to assess which of the two presented higher potential to stand out under conditions of competition. The trial was set in a greenhouse in completely randomized block design and 2 x 6 factorial scheme with four replications. Factor A consisted of rice varieties (hybrid or inbred) and factor B by competition levels. Treatments consisted in maintaining one plant of either BRS Pelota (inbred) or Inov (hybrid) variety at the center of the plot, under competition with 0, 1, 2, 3, 4 or 5 plants of the variety BRS Pelota at the periphery of the experimental unit, according to the treatment. Fifty days after emergence (DAE), sub-stomatal CO 2 concentration (Ci -mmol mol) and CO 2 consumed (DC -mmol mol) were quantified, as well as shoot dry mass (SDM). Hybrid plants present higher photosynthesis capacity than inbred plants, when competing with up to 3 times its own density. When under the same competitive intensity, hybrid plants surpass the inbred. However, it should be emphasized that, when in farm condition, the lower competitive capacity with weeds often attributed to the hybrid varieties, probably is due to their lower planting density, but if weed competition is kept at low levels, hybrid rice plants may perform in the same way or usually better than inbred plants.Keywords: competitive ability, plant physiology, Oryza sativa.RESUMO -Objetivou-se com este estudo avaliar características relacionadas a capacidade fotossintética de variedades de arroz híbridas e convencionais, de forma a quantificar seu potencial de competição. O experimento foi instalado em casa de vegetação em delineamento experimental de blocos casualizados e esquema fatorial 2 x 6, com quatro repetições. O fator A consistiu de variedades de arroz (convencional e híbrida) e o fator B de níveis de competição. Os tratamentos consistiram em manter uma planta da variedade BRS Pelota (convencional) ou Inov (híbrida) no centro da unidade experimental, sob competição com 0, 1, 2, 3, 4 ou 5 plantas da variedade BRS Pelota na periferia, de acordo com o tratamento. Cinquenta dias após a emergência (DAE), concentração de CO 2 subestomática (Cimmol mol -1 ), taxa fotossintética (A -mmol m 2 s 1 ) e CO 2 consumido durante a avaliação (DC -mmol mol -1 ) foram quantificados, bem como a massa seca da parte aérea das plantas (SDM). Plantas híbridas apresentaram maior capacidade fotossintética que as convencionais, quando sob competição com até três vezes sua própria densidade. Sob mesma intensidade de competição, plantas híbridas são superiores as convencionais. No entanto, deve-se enfatizar que em condições de campo a menor habilidade competitiva com plantas daninhas normalmente atribuída as variedades híbridas, provavelmente se deve a sua menor densidade de semeadura, mas se a densidade de plantas daninhas é mantida em níveis adequados plantas híbridas de arroz podem apresentar desempenho similar ou normalmente...

Crescimento e produtividade de milho em função da cultura antecessora

“…A análise de crescimento é uma técnica que detalha a alocação e partição de fotossintatos, em função da idade da planta (Falqueto et al 2009, Concenço et al 2011, Alvarez et al 2012 das extremidades das linhas, foram consideradas bordadura. A dessecação das plantas, para formação de cobertura do solo, foi realizada 15 dias antes da semeadura (DAS) do milho, na dose de 6,0 L ha -1 de glyphosate.…”

Trinexapac-Ethyl Affects Growth and Gas Exchange of Upland Rice

“…NAR was lower in both treatments at the physiological maturity stage than at the flowering stage (Table 1) (2011).…”

“…Gas exchange measures were carried out using a LI-6400 (Licor Inc. Lincoln, NE) portable photosynthesis open system, which measures CO 2 and water stem concentrations by infrared radiation, following the methodology proposed by Machado and Lagôa (1994) and Concenço et al (2011). Since gas exchange assessment is better during the greatest photosynthetic photon flux density (PPFD) and before the air temperature reaches the limit values for plants with the C3 photosynthetic mechanism (FEISTLER; HABERMANN, 2012;ALVAREZ et al, 2015), plants were evaluated between 9 am and 11 am.…”

“…The technique also assesses photosynthetic production by means of dry matter accumulation, allowing a better understanding of the factors that affect grain yield (URCHEI; RODRIGUES; STONE, 2000;FALQUETO et al, 2009;NASCENTE, 2012a;OLIVEIRA et al, 2013). Furthermore, grain yield in rice and other cereals is related to the amount of CO 2 fixed by the plant and to the partitioning of the photosynthesized substrate for the growth of grains and of other plant organs (TAIZ;ZEIGER, 2009;CONCENÇO et al, 2011;FAGERIA;MORAES;VASCONCELOS, 2011).Thus, the objective of this study was to assess the influence of the application of trinexapac-ethyl on upland rice crops through the analysis of plant growth and gas exchange.…”

Soybean growth and yield under cover crops

“…In addition, the growth analysis describes the morphological and physiological changes in a plant as a function of time and also evaluates the dry matter accumulation (Falqueto et al, 2009;Concenço et al, 2011). It contains basic information of the crop production and can be performed without the need for sophisticated equipment (Falqueto et al, 2009).…”