title: Chloroplast acclimation in leaves of Guzmania monostachia in response to high light.
abstract: Acclimation of leaves to high light (HL; 650 micromol m(-2) s(-1)) was investigated in the long-lived epiphytic bromeliad Guzmania monostachia and compared with plants maintained under low light (LL; 50 micromol m(-2) s(-1)). Despite a 60% decrease in total chlorophyll in HL-grown plants, the chlorophyll a/b ratio remained stable. Additionally, chloroplasts from HL-grown plants had a much lower thylakoid content and reduced granal stacking. Immunofluorescent labeling techniques were used to quantify the level of photosynthetic polypeptides. HL-grown plants had 30% to 40% of the content observed in LL-grown plants for the light-harvesting complex associated with photosystems I and II, the 33-kD photosystem II polypeptide, and Rubisco. These results were verified using conventional biochemical techniques, which revealed a comparable 60% decrease in Rubisco and total soluble protein. When expressed on a chlorophyll basis, the amount of protein and Rubisco was constant for HL- and LL-grown plants. Acclimation to HL involves a tightly coordinated adjustment of photosynthesis, indicating a highly regulated decrease in the number of photosynthetic units manifested at the level of the content of light-harvesting and electron transport components, the amount of Rubisco, and the induction of Crassulacean acid metabolism. This response occurs in mature leaves and may represent a strategy that is optimal for the resource-limited epiphytic niche.
authors.affiliation: Department of Agricultural and Environmental Science, King George VI Building, The University, Newcastle upon Tyne NE1 7RU, United Kingdom. kate.maxwell@newcastle.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Maxwell
authors.forename: J L
authors.initials: JL
authors.lastname: Marrison
authors.forename: R M
authors.initials: RM
authors.lastname: Leech
authors.forename: H
authors.initials: H
authors.lastname: Griffiths
authors.forename: P
authors.initials: P
authors.lastname: Horton
mesh_terms: D002734:Chlorophyll / Q000032:analysis; D002736:Chloroplasts / Q000737:chemistry* / Q000201:enzymology / Q000502:physiology* / Q000648:ultrastructure; D005455:Fluorescent Antibody Technique; D007425:Intracellular Membranes / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D008027:Light; D045342:Light-Harvesting Protein Complexes; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D008854:Microscopy, Electron; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism; D045332:Photosystem II Protein Complex; D018515:Plant Leaves / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D010940:Plant Proteins / Q000032:analysis; D012273:Ribulose-Bisphosphate Carboxylase / Q000032:analysis
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D010730:Phosphoenolpyruvate Carboxylase; D012273:Ribulose-Bisphosphate Carboxylase