Effects of Illumination Intensity, 5-aminolevulinic Acid Concentration and Their Interaction on Chlorophyll Fluorescence Parameters and Yield of Summer Maize

[Objective] This study aimed to investigate the influence of illumination intensity, 5-aminolevulinic acid （ALA） concentration and their interaction on chlorophyll fluorescence parameters and yield of summer maize. [Method] Two illumination intensity levels and five ALA concentrations were applied in the experiment using 2x5 completely balanced program. The two illumination intensity levels were natural light （So） and 60% shade （SO, and five ALA concentrations were 0, 1, 10, 25 and 50 mg/L. [Result] The relative chlorophyll content of leaf （SPAD）, the optimal/maximal quantum yield of PS II （Fv/Fm）, the photochemical quenching coefficient （qP）, electron transport rate （ETR）, grain number per cob and grain weight per cob in $1 treatment were significantly reduced compared with that in So. However, the non- photochemical quenching coefficient （qN） was significantly increased. The responses of these parameters to ALA were different under So and $1 treatments. The SPAD, Fv/Fm, qP, ETR, grain number and grain weight per cob were firstly increased, but then decreased following the raise of ALA concentration, ranging from 0 to 50 mg/L, whereas qN showed opposite trend. The effect of the interaction of illumination in- tensity and ALA concentration on these parameters was significant （P〈0.05）. Under natural light, summer maize could obtain higher SPAD, Fv/Fm, qP and ETR and lower qN combined with low concentration of ALA. However, high concentration of ALA was needed under shading to get the same results. [Conclusion] Soaking seed in suitable concentration of ALA can reduce the yield loss of summer maize caused by short-term shading in seedling stage.

Rapid microwave irradiation fast preparation and characterization of few-layer graphenes

Few-layer graphenes were fabricated from expandable graphite by rapid microwave exfoliation. Expandable graphite was irradiated in a domestic microwave in full power for 3 min, then soaked in mixed strong hydrogen nitrate and sulfuric acid with volume ratio of 1：1 for 24 h and re-irradiated, thus few-layer graphene sheets were obtained. Specimens gained from every step were selectively characterized by different techniques, such as SEM, XRD, Raman, AFM, XPS, FTIR and combustion elemental analysis. The results show that expandable graphite with loose, porous and worm-like morphology forms instantaneously in microwave irradiation with crackling sound and sparkles, which manifests physical exfoliation of graphene sheets. Few-layer graphene sheets with a dozen or more layers and average thickness of about 4.7 nm are obtained eventually after sequential treatment of microwave irradiation, mixed acid soaking and second microwave irradiation. The as-prepared few-layer graphenes still have high crystallinity and high purity with traces of oxide groups and without serious unrecoverable oxidation damage.