Effects of Doubled_CO_2 Concentration on Ultrastructure, Supramolecular Architecture and Spectral Characteristics of Chloroplasts from Wheat

Wheat ( Triticum aestivum L.) plants were grown under ambient and doubled_CO 2(plus 350 μL/L) concentration in cylindrical open_top chamber to examine their effects on the ultrastructure, supramolecular architecture, absorption spectrum and low temperature (77 K) fluorescence emission spectrum of the chloroplasts from wheat leaves. The results were briefly summarized as follows: (1) The wheat leaves possessed normally developed chloroplasts with intact grana and stroma thylakoid membranes; The grana intertwined with stroma thylakoid membranes and increased slightly in stacking degree and the width of granum, in spite of more accumulated starch grains within the chloroplasts than those in control; (2) The particle density in the stacked region of the endoplasmic fracture face (EFs) and protoplasmic fracture face (PFs) and in the unstacked region the endoplasmic fracture face (EFu) and the protoplasmic fracture face (PFu) was significantly higher than that of control. Furthermore, in some cases many more particles on EFs faces of thylakoid membranes appeared as a paracrystalline particle array; (3) The variations in the structure of chloroplasts were consistent with the absorption spectra and the low temperature (77 K) fluorescence emission spectra of the chloroplasts developed under the doubled_CO 2 concentration. Results indicate that the capability of light energy absorption of chloroplasts and regulative capability of excitation energy distribution between PSⅡ and PSⅠ were raised by doubled_CO 2 concentration. This is very favorable for final productivity of wheat.

Elemental composition x-ray fluorescence analysis with a TES-based high-resolution x-ray spectrometer

The accurate analysis of the elemental composition plays a crucial role in the research of functional materials.The emitting characteristic x-ray fluorescence(XRF)photons can be used for precisely discriminating the specified element.The detection accuracy of conventional XRF methodology using semiconductor detector is limited by the energy resolution,thus posing a challenge in accurately scaling the actual energy of each XRF photon.We adopt a novel high-resolution x-ray spectrometer based on the superconducting transition-edge sensor(TES)for the XRF spectroscopy measurement of different elements.Properties including high energy resolution,high detection efficiency and precise linearity of the new spectrometer will bring significant benefits in analyzing elemental composition via XRF.In this paper,we study the Ledge emission line profiles of three adjacent rare earth elements with the evenly mixed sample of their oxide components:terbium,dysprosium and holmium.Two orders of magnitude better energy resolution are obtained compared to a commercial silicon drift detector.With this TES-based spectrometer,the spectral lines overlapped or interfered by background can be clearly distinguished,thus making the chemical component analysis more accurate and quantitative.A database of coefficient values for the line strength of the spectrum can then be constructed thereafter.Equipped with the novel XRF spectrometer and an established coefficient database,a direct analysis of the composition proportion of a certain element in an unknown sample can be achieved with high accuracy.

Effects of Chlorophyll Availability on Fluorescence Components of Photosystems in the ORF_469-Deletion Mutant of Cyanobacterium

PCR amplified ORF 469 fragment from Synechocystis sp . PCC 6803 was cloned into pUC118 and a construct was made in which part of ORF 469 was deleted and replaced by erythromycin resistance cassette. Transformation of wild type strain of Synechocystis sp . PCC 6803 with this construct yielded a mutant in which ORF 469 was deleted. In the resulting mutant, the light independent pathway of chlorophyll biosynthesis was inactivated and availability of chlorophyll was fully dependent on light. When propagated the mutant in dark, the chlorophyll was non detectable and protochlorophyllide with 645?nm fluorescence emission peak was accumulated. Meanwhile, the fluorescence emission peaks (excited at 435?nm) of thylakoids at 685?nm, 695?nm and 725?nm, which represented relative chlorophyll\|binding proteins, disappeared. Upon return of dark\|grown ORF 469 mutant to the light, greening occurred and chlorophyll was synthesized to assembly fluorescence emission components in photosystems. Newly synthesized chlorophyll combined the fluorescence component of 685?nm at first, then 725?nm and 695?nm at last, which indicates a pecking order for biogenesis of chlorophyll binding proteins when availability of chlorophyll is limited. The mutant lacking ORF 469 in Synechocystis sp . PCC 6803 was suggested as an excellent cyanobacterial system for studies on the interactions between chlorophyll and chlorophyll binding proteins in photosystems.