Atividade fotossintética em folhas e pseudobulbos de Cattleya warneri (CAM) e Miltonia spectabilis (C3) sob défict hídrico

• Autor(a) principal: Zampirollo, Jadson Bonini
• 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/10/5253
• topic: Chlorophyll a fluorescence; Photochemical activity; Photosynthetic pigments; Relative water content; WD tolerance; Cattleya warneri; Miltonia spectabilis; Orchidaceae; Pigmentos cloroplastídicos; Déficit hídrico; Atividade fotoquímica; Conteúdo relativo de água; Fluorescência da clorofila a; Pigmentos fotossintéticos; Tolerância ao DH; Ecologia; Fotossíntese; Orquídea; 502

In this study ecophysiological characteristics were evaluated in leaves and pseudobulbs of epiphytic orchids species with CAM (Cattleya warneri T. Moore) and C3 (Miltonia spectabilis Lindl.) metabolism under prolonged water deficit (WD) (0, 15, 30, 45, 60, 75, and 90 days). For this, C. warneri and M. spectabilis plants obtained from a nursery in João Neiva/ES were transferred to nursery in UFES - Campus de São Mateus/ES, where chlorophyll a fluorescence transient, relative water content (RWC) and photosynthetic pigments were measured in leaves and pseudobulbs. Under WD, the RWC was significantly reduced in leaves and pseudobulbs of both species, however, in a similar way between the organs of CAM species (as from 30 days of WD - WD-30) and more slowly in the leaves in relation to pseudobulbs in C3 species (as from WD-60 and WD-30, respectively). The photosynthetic pigments concentration also were changed in response to water deficit, with declines observed in the chlorophyll a, b and total and increases of carotenoids in the leaves of both species, with increases in all of these pigments in the pseudobulbs of C. warneri, and no change in M. spectabilis. Chlorophyll a fluorescence parameters revealed increases in O-J and J-I phases, L and K-Bands, F0, ABS/RC, DI0/RC and decreases in the I-P phase, FV/FM, ET0/TR0, ET0/ABS e PITOTAL in leaves and pseudobulbs of both species, but more markedly in the pseudobulbs of M. spectabilis and with certain similarity between leaves and pseudobulbs of C. warneri. Thus, it is noted that both species demonstrated vulnerable to prolonged WD, with declines in the RWC, photodestruction of photosynthetic pigments and declines in photochemical activities, especially after the WD-30. However, the better maintenance of RWC values and smaller loss of performance of photochemical reactions observed in leaves of C3 species, M. spectabilis, associated with greater engagement of pseudobulbs indicate that this species is more tolerant to prolonged WD. The explanation for this may be the fact that senescent leaves, and mainly pseudobulbs are acting as facilitators organs in the in mobilization of water more effectively in this species, allowing the maintenance of the highest RWC on young leaves with consequent maintenance of photochemical activities.