Role of nitric oxide in hydrogen peroxide-dependent induction of abiotic stress tolerance by brassinosteroids in cucumber.

Brassinosteroids (BRs) can induce plant tolerance to a variety of abiotic stresses by triggering the generation of H(2) O(2) as a signalling molecule in cucumber leaves. Whether nitric oxide (NO) also plays a signalling role and, if so, what is the relationship between NO and H(2) O(2) in BR-induced stress tolerance are unknown. Involvement of NO and H(2) O(2) in BR-induced tolerance was examined. NO accumulation and defence related gene transcripts were monitored by confocal laser-scanning microscopy and qRT-PCR, respectively. NO content was elevated after treatment with 24-epibrassinolide (EBR) and reduced with the inhibition of BR biosynthesis. EBR-induced NO production was blocked by pre-treatment with inhibitor of NADPH oxidase and a reactive oxygen species scavenger. On the other hand, EBR-induced H(2) O(2) generation was not sensitive to NO scavenger or inhibitor of NO production. Scavenging or inhibition of NO production inhibited EBR-induced tolerance to photo-oxidative and cold stress and partly blocked EBR-induced expression and activities of several antioxidant enzymes. Pre-treatment of the exogenous NO precursor, on the other hand, led to both increased stress tolerance and increased expression of antioxidant enzymes. These results strongly suggest that NO plays an important role in H(2) O(2) -dependent induction of plant stress tolerance by BR.

A Co-MOF with a (4,4)-connected binodal two-dimensional topology: synthesis, structure and photocatalytic properties.

The Co-MOF poly[[diaqua{µ4-1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene-κ4N:N':N'':N'''}cobalt(II)] benzene-1,4-dicarboxylic acid benzene-1,4-dicarboxylate], {[Co(C34H24N12)(H2O)2](C8H4O4)·C8H6O4}n or {[Co(ttpe)(H2O)2](bdc)·(1,4-H2bdc)}n, (I), was synthesized by the hydrothermal method using 1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene (ttpe), benzene-1,4-dicarboxylic acid (1,4-H2bdc) and Co(NO3)2·6H2O, and characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD), luminescence, optical band gap and valence band X-ray photoelectron spectroscopy (VB XPS). Co-MOF (I) shows a (4,4)-connected binodal two-dimensional topology with a point symbol of {44·62}{44·62}. The two-dimensional networks capture free neutral 1,4-H2bdc molecules and bdc2- anions, and construct a three-dimensional supramolecular architecture via hydrogen-bond interactions. MOF (I) is a good photocatalyst for the degradation of methylene blue and rhodamine B under visible-light irradiation and can be reused at least five times.

Sonochemical synthesis and characterization of four nanostructural nickel coordination polymers and photocatalytic degradation of methylene blue.

Four nanostructural nickel(II) coordination polymers {[Ni(ttpa)(1,4-ndc)(H2O)2]·2H2O}n (1), {[Ni(ttpa)(1,3-bda)]·2H2O·DMF}n (2·2H2O·DMF), {[Ni(ttpa)(1,4-bdc)]·H2O}n (3) and {[Ni(ttpa)(aip)(H2O)]·3H2O}n (4·3H2O) were synthesized using hydrothermal and sonochemical methods (ttpa = tris(4-(1,2,4-triazol-1-yl)phenyl)amine, 1,4-ndc = 1,4-naphthalenedicarboxylate, 1,3-bda = 1,3-benzenediacetate, 1,4-bdc = 1,4-benzenedicarboxylate, aip = 5-aminoisophthalate), and characterized by elemental analysis, IR spectra, scanning electron microscopy, single-crystal and powder X-ray diffraction analysis, optical band gaps, VB XPS spectra and luminescence. The effects of sonication power, time and frequency on the size and morphology of nano-sized 1-4 have been studied. 1 exhibits an unusual 2D + 2D → 3D inclined polycatenated motif based on the (3,3)-coordinated 63-hcb topology. 2 shows a (3,4)-coordinated 2D network of the bey topology. 3 presents a rare example of the 4-fold interpenetrating array of (3,5)-coordinated 3D network belonging to the 35T1 topology type. 4 displays an unusual 2D → 3D polythreaded network based on 2D sql networks. 1-4 exhibit luminescent emissions at 409, 399, 413 and 402 nm, respectively. 1-4 are semiconducting in nature, with Eg of 2.12 eV (1), 2.34 eV (2), 2.32 eV (3), and 2.47 eV (4). 1-4 are good catalysts for the degradation of MB under visible light irradiation. The effects of the size and morphology of nano-sized 1-4 on the photocatalytic efficiencies were studied. The higher sonication frequency obtains uniform and smaller nano-sized coordination polymers which have higher catalytic efficiencies.