Effects of iron deficiency on photosynthesis and photosystem II function in soybean leaf.
Gas exchange and chlorophyll a fluorescence in soybean plants were investigated to explore the effects of iron deficiency on photosynthesis and photosystem II function in vivo. Iron deficiency induced a drastic decrease in net photosynthesis (Pn). Compared with normal plants, the maximal quantum yield of PSII photochemistry (psipo) in iron-deficient plants was only slightly lower; whereas, the efficiency with which a trapped exciton can move an electron into the electron transport chain further than QA-(Psio) and quantum yield of electron transport beyond QA (psiEo) were significantly depressed. Iron deficiency also caused a clear enhancement of the relative variable fluorescence at K step (VK). When exposed to light, iron-deficient plants had considerably lower efficiency of excitation energy capture by open PSII reaction centers (Fv'/Fm'), quantum yield of PSII electron transport (PhiPSII), and photochemical quenching coefficient (qP), but markedly higher non-photochemical quenching (NPQ). In addition, post-illumination transient increase in chlorophyll fluorescence was clearly enhanced in iron-deficient plants. Basing on these data, we suggest that both the donor and the acceptor sides of PSII complex were damaged by iron deficiency; cyclic electron transport around PSI in iron-deficient soybean plants might play an important role in inducing the excitation energy dissipation and meeting the demand for extra ATP as a compensation for the loss of phosphorylation capability.
Jiang
Chuang-Dao
CD
Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
Gao
Hui-Yuan
HY
Zou
Qi
Q
Shi
Lei
L
D002734:Chlorophyll / Q000737:chemistry / Q000378:metabolism; D004553:Electric Conductivity; D005453:Fluorescence; D000090463:Iron Deficiencies; D019189:Iron Metabolism Disorders / Q000378:metabolism* / Q000503:physiopathology; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism* / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D013025:Glycine max / Q000502:physiology
D045332:Photosystem II Protein Complex; D002734:Chlorophyll