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J Plant Physiol ; 266: 153510, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34521019


Source sink balance is one of the major determinants of carbon partitioning in plants. However, its effects on photosynthesis in fruit trees are largely unknown. In this work, the effects of low sink demand on net photosynthetic rate (Pn) and chlorophyll fluorescence after fruit removal (-fruit) in peach (Prunus persica (L.) Batsch cv. 'Zaojiubao') trees were investigated. The stepwise energy flow through photosystem II (PSII) at the reaction center (RC) was analyzed with quantitative analyses of fluorescence transient, also called JIP-test. We found that Pn was significantly lower and closely correlated to the leaf stomatal conductance (Gs) of -fruit trees than that of fruit retained (+fruit) trees. Leaf temperature (Tleaf) of -fruit trees was remarkably higher than that of +fruit trees. Day-time-period assays of chlorophyll (Chl) fluorescence revealed that, in the leaves of -fruit trees, the fluorescence parameters, such as NPQ (non-photochemical quenching coefficient) and ΦD0 (maximum quantum yield of non-photochemical de-excitation), decreased in the morning and recovered to the normal level in the afternoon, whereas other parameters, such as ΦE0 (quantum yield for electron transport at t = 0), Ψ0 (probability that a trapped exciton moves an electron to QA pool), F0 (minimum fluorescence, when all PSII RCs are open) and Wk (relative variable fluorescence at 300 µs of the chlorophyll fluorescence transient), did not. These results suggest that OEC complex and QA pool were irreversibly affected by low sink demand, whereas light harvest antenna and PSII potential efficiency retained a strong ability to recover.

Surf Coat Technol ; 224: 101-108, 2013 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-23682201


This paper describes synthesis of ultrathin pinhole-free insulating aluminum oxide layers for electronic device protection in corrosive liquid environments, such as phosphate buffered saline (PBS) or clinical fluids, to enable emerging biomedical applications such as biomolecular sensors. A pinhole-free 25-nm thick amorphous aluminum oxide layer has been achieved using ultra-high vacuum DC magnetron reactive sputtering of aluminum in oxygen/argon plasma followed by oxygen plasma post-processing. Deposition parameters were optimized to achieve the best corrosion protection of lithographically defined device structures. Electrochemical deposition of copper through the aluminum oxide layers was used to detect the presence (or absence) of pinholes. FTIR, XPS, and spectroscopic ellipsometry were used to characterize the material properties of the protective layers. Electrical resistance of the copper device structures protected by the aluminum oxide layers and exposed to a PBS solution was used as a metric to evaluate the long-term stability of these device structures.

PLoS One ; 7(5): e37440, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22693574


Ion Beam Aperture Array Lithography was applied to top-down fabrication of large dense (10(8)-10(9) particles/cm(2)) arrays of uniform micron-scale particles at rates hundreds of times faster than electron beam lithography. In this process, a large array of helium ion beamlets is formed when a stencil mask containing an array of circular openings is illuminated by a broad beam of energetic (5-8 keV) ions, and is used to write arrays of specific repetitive patterns. A commercial 5-micrometer metal mesh was used as a stencil mask; the mesh size was adjusted by shrinking the stencil openings using conformal sputter-deposition of copper. Thermal evaporation from multiple sources was utilized to form magnetic particles of varied size and thickness, including alternating layers of gold and permalloy. Evaporation of permalloy layers in the presence of a magnetic field allowed creation of particles with uniform magnetic properties and pre-determined magnetization direction. The magnetic properties of the resulting particles were characterized by Vibrating Sample Magnetometry. Since the orientation of the particles on the substrate before release into suspension is known, the orientation-dependent magnetic properties of the particles could be determined.

Imãs/química , Nanopartículas/química , Nanotecnologia/métodos , Anisotropia , Engenharia , Fenômenos Magnéticos , Tamanho da Partícula , Impressão , Silício/química
Artigo em Inglês | MEDLINE | ID: mdl-15840935


There are many reports about the correlation between small molecular heat-shock protein (sHSP) and the acquirement of chilling tolerance, but no direct evidence that sHSP confers enhanced chilling tolerance to plant has been reported. A DNA construct, including tomato chloroplast-localized small molecular heat-shock protein (CPsHSP) cDNA under the control of cauliflower mosaic virus 35S (35SCaMV) promoter, was introduced into the genome of tomato plants. The chilling tolerance of the transgenic tomato lines and the non-transgenic tomato was evaluated. After exposure to chilling stress, the transgenic plants exhibited lighter chilling-injured symptoms, suffered less electrolyte leakage and less destruction of chlorophyll, accumulated less anthocyanins and less MDA and kept higher value of net photosynthetic rate, than non-transgenic plant. All results indicated consistently that transgenic tomato plants had stronger chilling tolerance. These characters are ascribed to constitutive expression of cpshsp and lead to the conclusion that HSP can enhance chilling tolerance in plant.

Cloroplastos/metabolismo , Temperatura Baixa , Proteínas de Choque Térmico Pequenas/fisiologia , Lycopersicon esculentum/fisiologia , Plantas Geneticamente Modificadas/fisiologia , Aclimatação/genética , Aclimatação/fisiologia , Antocianinas/metabolismo , Clorofila/metabolismo , Regulação da Expressão Gênica de Plantas , Proteínas de Choque Térmico Pequenas/genética , Proteínas de Choque Térmico Pequenas/metabolismo , Lycopersicon esculentum/genética , Lycopersicon esculentum/metabolismo , Fotossíntese/fisiologia , Plantas Geneticamente Modificadas/genética , Plantas Geneticamente Modificadas/metabolismo