Redox basis of photosynthesis inhibition at supra-optimal bicarbonate in mesophyll protoplasts of Arabidopsis thaliana.

We examined the patterns of photosynthetic O evolution at 1 mM (optimal) and 10 mM (supra-optimal) bicarbonate in mesophyll protoplasts of Arabidopsis thaliana. The photosynthetic rate of protoplasts reached the maximum at an optimal concentration of 1 mM bicarbonate and got suppressed at supra-optimal levels of bicarbonate. We examined the basis of such photosynthesis inhibition by mesophyll protoplasts at supra-optimal bicarbonate.

Modulation of Photorespiratory Enzymes by Oxidative and Photo-Oxidative Stress Induced by Menadione in Leaves of Pea ().

Photorespiration, an essential component of plant metabolism, is concerted across four subcellular compartments, namely, chloroplast, peroxisome, mitochondrion, and the cytoplasm. It is unclear how the pathway located in different subcellular compartments respond to stress occurring exclusively in one of those. We attempted to assess the inter-organelle interaction during the photorespiratory pathway.

Photosynthesis is sensitive to nitric oxide and respiration sensitive to hydrogen peroxide: Studies with pea mesophyll protoplasts.

Reports on the effect of nitric oxide (NO) or reactive oxygen species (ROS) on photosynthesis and respiration in leaf tissues are intriguing; therefore, the effects of exogenous addition of sodium nitroprusside (SNP, releases NO) or HO on the photosynthetic O evolution and respiratory O uptake by mesophyll protoplasts in pea (Pisum sativum) were evaluated in the present study. Low concentrations of SNP or HO were used to minimize nonspecific effects. The effects of NO or HO on respiration and photosynthesis were different.

Oxidative stress induced in chloroplasts or mitochondria promotes proline accumulation in leaves of pea (Pisum sativum): another example of chloroplast-mitochondria interactions.

Oxidative stress can occur in different parts of plant cells. We employed two oxidants that induce reactive oxygen species (ROS) in different intracellular compartments: methyl viologen (MV, in chloroplasts) and menadione (MD, in mitochondria). The responses of pea (Pisum sativum) leaf discs to MV or MD after 4-h incubation in dark or moderate (300 μE m s) or high light (1200 μE m s) were examined.

Stomatal closure induced by phytosphingosine-1-phosphate and sphingosine-1-phosphate depends on nitric oxide and pH of guard cells in Pisum sativum.

Phyto-S1P and S1P induced stomatal closure in epidermis of pea ( Pisum sativum ) by raising the levels of NO and pH in guard cells. Phosphosphingolipids, such as phytosphingosine-1-phosphate (phyto-S1P) and sphingosine-1-phosphate (S1P), are important signaling components during drought stress. The biosynthesis of phyto-S1P or S1P is mediated by sphingosine kinases (SPHKs).

Ascorbic acid is a key participant during the interactions between chloroplasts and mitochondria to optimize photosynthesis and protect against photoinhibition.

The possible role of L-ascorbate (AsA) as a biochemical signal during the interactions between photosynthesis and respiration was examined in leaf discs of Arabidopsis thaliana. AsA content was either decreased as in AsA-deficient vtc1 mutants or increased by treatment with L-galactono-1, 4-lactone (L-GalL, a precursor of AsA; EC 1.3.