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

• Published in: Planta daninha 2011-12, Vol.29 (4), p.803-809
• Main Authors: Concenço, G, Aspiazú, I, Galon, L, Ferreira, E.A, Freitas, M.A.M, Fialho, C.M.T, Schwanke, A.M.L, Ferreira, F.A, Silva, A.A
• Format: Article
• Language: English
• Subjects: PLANT SCIENCES
• ISSN: 0100-8358; 1806-9681; 0100-8358
• DOI: 10.1590/S0100-83582011000400010

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 CO2 concentration (Ci - mmol mol-1), photosynthetic rate (A - mmol m-2 s-1) and CO2 consumed (DC - mmol mol-1) 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. 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 CO2 subestomática (Ci - mmol mol-1), taxa fotossintética (A - mmol m² s¹) e CO2 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