title: Effects of season-dependent irradiance levels and nitrogen-deficiency on photosynthesis and photoinhibition in field-grown rice (Oryza sativa).
abstract: Photoinhibition and acclimation of photosynthesis in rice plants grown under N-sufficient (NS) and N-deficient (ND) field conditions were investigated during the tropical wet (WS) and dry (DS) seasons in the Philippines. Diurnal patterns of CO2 assimilation were examined. There was a transient peak in CO2 assimilation in the leaves of the NS plants in the early morning during the DS and the WS, which was not seen in the ND plants in either season. ND leaves had lower Ribulose bisphosphate carboxylase/oxygenase (Rubisco) contents and lower chlorophyll contents. A lowered quantum yield of photosystem II (phiPSII) was observed in the ND plants at an intermediate irradiance though no differences between N treatments were seen at high irradiance. Analysis of carotenoids indicated a small increase in the de-epoxidation state of the xanthophyll cycle (DES) at mid-day in the ND leaves compared to NS. Photoinhibition was greater in ND leaves when incident mid-day irradiance was increased by altering the leaf angle. Although Rubisco contents were lower in ND plants, photosynthesis in situ did not decline proportionally. For NS plants, Chlorophyll content, but not Rubisco content, was season-dependent and results are discussed in terms of the interaction between irradiance use and N content of rice leaves.
authors.affiliation: Crop, Soil and Water Sciences Division, International Rice Research Institute, PO Box 933, 1099 Manila, Philippines Robert Hill Institute, Department of Molecular Biology and Biotechnology, Firth Court, Western Bank, University of Sheffield, Sheffield, S10 2TN, UK Present address: South China Institute of Botany, Academia Sinica, Leyiju, Guangzhou 510650, China.
authors.forename: Yizhu
authors.initials: Y
authors.lastname: Chen
authors.forename: Erik H
authors.initials: EH
authors.lastname: Murchie
authors.forename: Stella
authors.initials: S
authors.lastname: Hubbart
authors.forename: Peter
authors.initials: P
authors.lastname: Horton
authors.forename: Shaobing
authors.initials: S
authors.lastname: Peng