title: Responses of the photosynthetic apparatus to winter conditions in broadleaved evergreen trees growing in warm temperate regions of Japan.
abstract: Photosynthetic characteristics of two broadleaved evergreen trees, Quercus myrsinaefolia and Machilus thunbergii, were compared in autumn and winter. The irradiance was similar in both seasons, but the air temperature was lower in winter. Under the winter conditions, net photosynthesis under natural sunlight (Anet) in both species dropped to 4 μmol CO2 m(-2) s(-1), and the quantum yield of photosystem II (PSII) photochemistry in dark-adapted leaves (Fv/Fm) also dropped to 0.60. In both species the maximum carboxylation rates of Rubisco (V(cmax)) decreased, and the amount of Rubisco increased in winter. A decline in chlorophyll (Chl) concentration and an increase in the Chl a/b ratio in winter resulted in a reduction in the size of the light-harvesting antennae. From measurements of Chl a fluorescence parameters, both the relative fraction and the energy flux rates of thermal dissipation through other non-photochemical processes were markedly elevated in winter. The results indicate that the photosynthetic apparatus in broadleaved evergreen species in warm temperate regions responds to winter through regulatory mechanisms involving the downregulation of light-harvesting and photosynthesis coupled with increased photoprotective thermal energy dissipation to minimize photodamage in winter. These mechanisms aid a quick restart of photosynthesis without the development of new leaves in the following spring.
authors.affiliation: Department of Biology, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan.
authors.forename: Chizuru
authors.initials: C
authors.lastname: Tanaka
authors.affiliation: Mount Fuji Research Institute, Yamanashi Prefectural Government (MFRI), Kenmarubi 5597-1, Kamiyoshida, Fujiyoshida City, Yamanashi 403-0005, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakano
authors.affiliation: Department of Biology, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan. Electronic address: junya@bio.sci.toho-u.ac.jp.
authors.forename: Jun-Ya
authors.initials: JY
authors.lastname: Yamazaki
authors.affiliation: Department of Biology, Faculty of Science, Toho University, Miyama 2-2-1, Funabashi, Chiba 274-8510, Japan.
authors.forename: Emiko
authors.initials: E
authors.lastname: Maruta
mesh_terms: D000465:Algorithms; D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D007564:Japan; D019770:Lauraceae / Q000378:metabolism / Q000502:physiology*; D015227:Lipid Peroxidation / Q000528:radiation effects; D055668:Photochemical Processes / Q000528:radiation effects; D010788:Photosynthesis / Q000502:physiology* / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism / Q000502:physiology; D029963:Quercus / Q000378:metabolism / Q000502:physiology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D012621:Seasons; D013472:Sunlight; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; C037184:chlorophyll b; D012273:Ribulose-Bisphosphate Carboxylase; D000077194:Chlorophyll A
keywords: Broadleaved evergreens; Energy flux; Energy partition; Machilus thunbergii; Quercus myrsinaefolia