Dissipation of Excess Energy in Mehler-Peroxidase Reaction in Rumex Leaves During Salt Shock

Abstract

By measurement of gas exchange and chlorophyll fluorescence, the effects of salt shock on photosynthesis and the mechanisms to protect photosynthetic machinery against photodamage during salt shock were investigated in leaves of Rumex seedlings. Salt shock induced significant decrease in photosynthesis both in 21 and 2 % O 2 . In 21 % O 2 , quantum yield of photosystem 2 (PS2) electron transport (Ф PS2 ) decreased slightly and q P remained constant, suggesting that the excitation pressure on PS2 did not increase during salt shock. In 2 % O 2 , however, both Ф PS2 and q P decreased significantly, suggesting that the excitation pressure on PS2 increased during salt shock. NPQ increased slightly in 21 % O 2 whereas it increased significantly in 2 % O 2 . The data demonstrated that during salt shock a considerable electron flow was allocated to oxygen reduction in the Mehler-peroxidase reaction (MPR). Under high irradiance and in the presence of saturating CO 2 , the susceptibility of PS2 to photoinhibition in salt-shocked leaves was increased when the electron flow to oxygen in MPR was inhibited in 2 % O 2 . Hence, MPR is important in photoprotection of Rumex seedlings during salt shock.

Contrasting Responses of Photosynthesis to Salt Stress in the Glycophyte Arabidopsis and the Halophyte Thellungiella: Role of the Plastid Terminal Oxidase as an Alternative Electron Sink

“…It will provide a sink for reductant, taking electrons away from the electron transport chain and so tend to protect PSII from photoinhibition. It is also believed to generate a DpH across the thylakoid membrane, supporting protective, NPQ of energy (Asada, 2000;Chen et al, 2004); however, it is liable to produce ROS. These are tightly controlled by coupling the Mehler reaction to detoxifying processes (Asada, 2000), but will still impose a metabolic burden on the plant.…”

Reduced photosynthetic dark reaction triggered by ABA application increases intercellular CO2 concentration, generates H2O2 and promotes closure of stomata in ginger leaves

“…The conversion of glycolic acid to glyoxylic acid during photorespiration also produces H 2 O 2 (Fahnenstich et al, 2008). The photosynthetic dark reaction affects the photorespiration magnitude and the Mehler reaction (Chen et al, 2004Zhou et al, 2004Li et al, 2013) and, consequently, the generation of H 2 O 2, . Ginger is native to tropical rain forests (Xu, 1999;Xu et al, 2003).…”

The higher resistance to chilling stress in adaxial side of Rumex K-1 leaves is accompanied with higher photochemical and non-photochemical quenching

“…With evolution, plants have possessed some ---protective mechanisms to alleviate stress damage such as non-photochemical quenching dependent on xanthophyll cycle (Demmig-Adams and Adams 1992, Dai et al 2004, Jiang et al 2005, photorespiration (Foyer andNoctor 2000, Jiang et al 2006a), water-water cycle (Asada 1999, Chen et al 2004, and so on. The high extinction of blue and red radiation at the adaxial side of leaves suggests the possibility that the adaxial side of leaves has greater capacity of non-photochemical quenching than the abaxial side (Sun et al 1998).…”