RESUMO
The effects of high-intensity light (HIL) on the activity of photosystem II (PSII) and photosynthesis in wild-type (WT) and single (phyB2, phyB1, phyA and cry1), double (phyB1B2, phyAB2 and phyAB1) and triple (phyAB1B2 and cry1phyAB1) mutants of Solanum lycopersicum were studied. In addition, changes in the activity of the antioxidant enzymes ascorbate peroxidase, glutathione reductase and guaiacol peroxidase as well as the photosynthetic pigment and anthocyanin contents in the leaves of phyB2 and cry1phAB1 mutants under HIL were examined. When plants were irradiated with HIL (2â¯h), the PSII resistance of the cry1phyAB1 mutant was the lowest, while the resistance of WT and single mutants excluding cry1 was the highest. The effect of HIL on PSII activity in all double mutants and the phyAB1B2 mutant was intermediate between the effects on the WT and the cry1phyAB1 mutant. The intensity of oxidative processes in the cry1phyAB1 mutant was higher than that in WT and phyB2, but in cry1phyAB1, the activity of antioxidant enzymes and the anthocyanin content were lower. The low resistance of the cry1phyAB1 mutant to HIL may be due to the low antioxidant activity of key enzymes and the reduced pigment content, which are consistent with the reduced expression of CHS and sAPX genes in the cry1phyAB1 mutant.
Assuntos
Criptocromos/genética , Luz , Fitocromo A/genética , Fitocromo B/genética , Solanum lycopersicum/efeitos da radiação , Antocianinas/química , Antocianinas/metabolismo , Ascorbato Peroxidases/metabolismo , Carotenoides/química , Carotenoides/metabolismo , Criptocromos/deficiência , Glutationa Redutase/metabolismo , Solanum lycopersicum/química , Solanum lycopersicum/metabolismo , Fotossíntese/efeitos da radiação , Fitocromo A/deficiência , Fitocromo B/deficiência , Folhas de Planta/química , Folhas de Planta/metabolismo , Folhas de Planta/efeitos da radiação , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Tolerância a RadiaçãoRESUMO
Phthalocyanines are a promising class of ligands for manganese because of their high binding affinity. This effect is suggested to be an important factor because phthalocyanines tightly bind manganese and stabilize it under moderate conditions. The strong donor power of phthalocyanine is also suggested as a critical factor to stabilize high-valent manganese phthalocyanine. Herein, a manganese(ii) phthalocyanine, which is stable under moderate conditions, was investigated under harsh electrochemical water oxidation. By scanning electron microscopy, transmission electron microscopy, energy dispersive spectrometry, X-ray diffraction, extended X-ray absorption fine structure analysis, X-ray absorption near edge structure analysis, chronoamperometry, magnetic measurements, Fourier-transform infrared spectroscopy, and electrochemical methods, it is shown that manganese phthalocyanine, a known molecular complex showing good stability under moderate conditions, could not withstand water oxidation catalysis and ultimately is altered to form catalytic oxide particles. Such nanosized Mn oxides are the true catalyst for water oxidation. Besides, we try to go a step forward to find an answer as to how Mn oxides form on the surface of the electrode.
