Effects of addition of external nitric oxide on the allocation of photosynthetic electron flux in Rumex K-1 leaves under osmotic shock

Abstract

Photosynthetic electron flux allocation, stomatal conductance, and the activities of key enzymes involved in photosynthesis were investigated in Rumex K-1 leaves to better understand the role of nitric oxide (NO) in photoprotection under osmotic stress caused by polyethylene glycol. Gas exchange and chlorophyll fluorescence were measured simultaneously with a portable photosynthesis system integrated with a pulse modulated fluorometer to calculate allocation of photosynthetic electron fluxes. Osmotic stress decreased stomatal conductance, photosynthetic carbon assimilation, and nitrate assimilation, increased Mehler reaction, and resulted in photoinhibition. Addition of external NO enhanced the stomatal conductance, photosynthetic rate, activities of glutamine synthetase and nitrate reductase, and reduced Mehler reaction and photoinhibition. These results demonstrated that osmotic stress reduced CO 2 assimilation, decreasing the use of excited energy via CO 2 assimilation which caused significant photoinhibition. Improving stomatal conductance by the addition of external NO enhanced the use of excited energy via CO 2 assimilation. As a result, less excited energy was allocated to Mehler reaction, which reduced production of reactive oxygen species via this pathway. We suppose that Mehler reaction is not promoted unless photosynthesis and nitrogen metabolism are prominently inhibited.

NO to drought-multifunctional role of nitric oxide in plant drought: Do we have all the answers?

“…Exogenous application of SNP during adventitious rooting in explants of Tagetes erecta reduced drought-induced reduction in photochemical quenching, thus facilitating the participation of more excited lightenergy in photochemical reactions [38]. Treatment with GSNO enhanced the photosynthetic rate in Rumex leaves under osmotic stress, apparently due to enhanced CO 2 assimilation that reduced the generation of ROS by inhibiting Mehler reaction [62]. Additionally, exogenous NO ameliorates drought stress by altering chlorophyll florescence and photosynthesis [32,61].…”

“…NO can acts as a chain breaker during lipid peroxidation by interacting with lipid alcoxyl and peroxyl radicals. In contrast, NO in milli to molar concentrations seems to cause nitrosative stress leading to protein, nucleic acid and membrane damage in plant cells[38,62] owing to its reaction with (O 2*− ) forming peroxynitrite which can destroy the structure and function of biological macromolecules[70]. Water deficit can induce both oxidative and nitrosative stress in plants where NO and ROS acts as signaling molecules.…”

Non-Photochemical Quenching Involved in the Regulation of Photosynthesis of Rice Leaves under High Nitrogen Conditions

“…Nitrogen (N) is the most important nutrient element in plants [1,2], and is present in proteins, nucleic acids, co-enzymes, and membranes, with important roles in metabolism. N metabolism is closely related to electronic transport in chloroplasts [3]. The allocation of N in the photosynthetic apparatus affects the photosynthetic rate and the photosynthetic N use efficiency [4][5][6].…”

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).…”