3a,11b-Dihydr­oxy-2-oxo-2,3,3a,11b-tetra­hydro-1H-imidazo[4,5-f][1,10]phenanthrolin-7-ium chloride

In the crystal structure of the title compound, C13H11N4O3 +·Cl−, the dihedral angle between the two pyridine rings is 9.72 (9) Å. Ions are linked via N—H⋯Cl, O—H⋯Cl and O—H⋯O hydrogen bonds, forming a three-dimensional framework

2-(2-Fur­yl)-1H-imidazo[4,5-f][1,10]phenanthroline-3,7-diium dichloride monohydrate

The organic cation of the title salt, C17H12N4O2+·2Cl−·H2O, is nearly planar, the dihedral angle between two pyridine rings being 2.53 (16)° and that between the pyridinum and furan rings being 4.17 (19)°. Mol­ecules are linked via N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds, forming a three-dimensional framework and π–π stacking inter­actions help to stabilize the crystal structure [the imidazole–pyridine and imidazole–benzene centroid–centroid distances are 3.501 (3) and 3.674 (3) Å; respectively]

Calcium-sensing receptor regulates stomatal closure through hydrogen peroxide and nitric oxide in response to extracellular calcium in Arabidopsis

The Arabidopsis calcium-sensing receptor CAS is a crucial regulator of extracellular calcium-induced stomatal closure. Free cytosolic Ca2+ (Ca2+i) increases in response to a high extracellular calcium (Ca2+o) level through a CAS signalling pathway and finally leads to stomatal closure. Multidisciplinary approaches including histochemical, pharmacological, fluorescent, electrochemical, and molecular biological methods were used to discuss the relationship of hydrogen peroxide (H2O2) and nitric oxide (NO) signalling in the CAS signalling pathway in guard cells in response to Ca2+o. Here it is shown that Ca2+o could induce H2O2 and NO production from guard cells but only H2O2 from chloroplasts, leading to stomatal closure. In addition, the CASas mutant, the atrbohD/F double mutant, and the Atnoa1 mutant were all insensitive to Ca2+o-stimulated stomatal closure, as well as H2O2 and NO elevation in the case of CASas. Furthermore, it was found that the antioxidant system might function as a mediator in Ca2+o and H2O2 signalling in guard cells. The results suggest a hypothetical model whereby Ca2+o induces H2O2 and NO accumulation in guard cells through the CAS signalling pathway, which further triggers Ca2+i transients and finally stomatal closure. The possible cross-talk of Ca2+o and abscisic acid signalling as well as the antioxidant system are discussed