Efeito da exposição a alta luminosidade no desempenho fotoquímico de Cattleya guttata (CAM) e Miltonia spectabilis (C3) - Orchidaceae

• Autor(a) principal: Marcarini, Lourdes
• Data de Publicação: 2016
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/5254
• topic: Cattleya guttata; Miltonia spectabilis; CAM metabolism; C3 metabolism; Photoinhibition and performance photochemical; Metabolismo CAM; Metabilismo C3; Fluorescência da clorofila a; Ecologia; Orquídea; Fotoinibição de plantas; Plantas x Metabolismo; Plantas x Efeito da luz; 502

Cattleya guttata Lindl. and Miltonia spectabilis Lindl. (Orchidaceae) are epiphytes that have carbon fixation metabolism CAM and C3 respectively. The light directly influences the growth and development of plants. However, excess, can cause the light photoinhibition, which, depending on the intensity of damage in the photosynthetic apparatus can be dynamic or chronic. Therefore, this study aimed to analyze the photochemical performance in C. guttata and M. spectabilis exposed to high brightness at different time intervals. Thus, plants grown in a greenhouse (220 ± 9,3 µmol m-2 s -1) were transferred to open, in irradiance 2330 ± 76 µmol m-2 s -1 for 5, 35 and 120 minutes (considered here as treatments T5, T35 and T120). Plants grown in the greenhouse were used as control. The analysis of chlorophyll fluorescence were made in the range of: -5 (measurement performed five hours prior to exposure of the plants to full sunlight). 0 (measured immediately performed after exposure of the plants to sunlight) and 1, 5, 19, 43 and 93 h (hours elapsed after exposure of the plants in order to assess recovery). We analyzed the concentration of photosynthetic pigments, the OJIP curves, L-band, K, and test parameters JIP. The concentration of photosynthetic pigments was higher in M. spectabilis, but this result did not give the species best photochemical performance against C. guttata. Curves with positive amplitude for the band L were obtained in both species in all treatments, indicating connectivity energy losses. It was observed, also, the appearance of K-band, with positive values T5 and T35 and negative at T120, showing a tendency of acclimatization oxygen evolving complex (OEC) to high light for both the CAM species as for the species C3. The values of the initial increase in fluorescence (F0) was accompanied by the reduction of the maximal fluorescence (Fm) and photochemical efficiency (Fv/Fm) in both species. The increase in the flux values of absorption of active reaction center (ABS/RC) was followed by increasing values of excitation energy dissipation flux (DI0/RC), suggesting mechanisms photoprotection. Reduced values of assets reaction centers per cross section (RC/CS0) and photochemical performance index [PI(total)] were observed in T35 and T120 in C. guttata, which occurred in M. spectabilis T120. In general, the observed changes in photosynthetic parameters in M. spectabilis were directly related to the time of exposure to sunlight, as well as the recovery time was proportional to the damage. For C. guttata, the absence of significant differences between T35 and T120 for most JIP test parameters analyzed suggests high light acclimation. The time required for the recovery of F0, Fm and Fv/Fm indicates the occurrence of dynamic photoinhibition and chronic in T35 and T120, respectively, for both species. Damage to the photosynthetic apparatus were more severe in M. spectabilis due to the increased time required for the recovery of photosynthetic parameters evaluated