title: Low night temperature acclimation of Phalaenopsis.
abstract: The capability of Phalaenopsis to acclimate its photosynthetic capacity and metabolic activity to cool night temperature conditions is crucial for improving orchid production in terms of efficient greenhouse heating. The extent to which Phalaenopsis possesses acclimation potential and the mechanistic background of the metabolic processes involved, have, however, not been studied before. Plants were subjected to a direct and gradual shift from a day to night temperature regime of 28/28-28/16°C, the cold stress and cold acclimation treatment, respectively. In comparison with the cold stress treatment, the cold acclimation treatment led to a higher malate accumulation and a reduction in leaf net CO(2) uptake. Consistently, the contribution of respiratory CO(2) recycling to nocturnal malate synthesis was calculated to be 23.5 and 47.0% for the cold stress and cold acclimation treatment, respectively. Moreover, the lower levels of starch measured in the cold acclimated leaves confirmed the suggested enhanced respiratory CO(2) recycling, implying that Phalaenopsis CAM operation evolved towards CAM idling. It is, however, plausible that this adjustment was not an effect of the low night temperature per se but a consequence of cool-root induced drought stress. Apart from that, at the start of the photoperiod, membrane stability showed a depression which was directly counteracted by an increased generation of glucose, fructose and sucrose. From these observations, it can be concluded that the observed plasticity in CAM operation and metabolic flexibility may be recognized as important steps in the low night temperature acclimation of Phalaenopsis.
authors.affiliation: Laboratory of Plant Ecology, Department of Applied Ecology and Environmental Biology, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, 9000 Ghent, Belgium. Bruno.Pollet@UGent.be
authors.forename: Bruno
authors.initials: B
authors.lastname: Pollet
authors.forename: Lynn
authors.initials: L
authors.lastname: Vanhaecke
authors.forename: Pieter
authors.initials: P
authors.lastname: Dambre
authors.forename: Peter
authors.initials: P
authors.lastname: Lootens
authors.forename: Kathy
authors.initials: K
authors.lastname: Steppe
mesh_terms: D000064:Acclimatization / Q000502:physiology*; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D002264:Carboxylic Acids / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D002940:Circadian Rhythm / Q000502:physiology; D003080:Cold Temperature; D003624:Darkness; D005453:Fluorescence; D029595:Orchidaceae / Q000166:cytology / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D013213:Starch / Q000378:metabolism
chemical_list: D002264:Carboxylic Acids; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D013213:Starch