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.

Microalgae Improve the Photosynthetic Performance of Rice Seedlings(Oryza sativa L.)under Physiological Conditions and Cadmium Stress

The aim of this study was to assess the impact of the microalgae Chlorella vulgaris on the rice seedlings at physiological conditions and under cadmium(Cd)stress.We examined the effects of C.vulgaris in the nutrient solution on rice seedlings grown hydroponically in the presence and the absence of 150μM CdCl2,using the low(77 K)temperature and pulse amplitude modulated(PAM)chlorophyll fluorescence,P700 photooxidation measurements,photochemical activities of both photosystems,kinetic parameters of oxygen evolution,oxidative stress markers(MDA,H_(2)O_(2) and proline),pigment content,growth parameters and Cd accumulation.Data revealed that the application C.vulgaris not only stimulates growth and improves the functions of photosynthetic apparatus under physiological conditions,but also reduces the toxic effect of Cd on rice seedlings.Furthermore,the presence of the green microalgae in the nutrient solution of the rice seedlings during Cd exposure,signifi-cantly improved the growth,photochemical activities of both photosystems,the kinetic parameters of the oxygen-evolving reactions,pigment content and decreased lipid peroxidation,H_(2)O_(2) and proline content.Data showed that the alleviation of Cd-induced effects in rice seedlings is a result of the Cd sorption by microalgae,as well as the reduced Cd accumulation in the roots and its translocation from the roots to the shoots.