Thermostability Of Photosynthetic Apparatus Research Articles

Hodnotenie fotosyntetických charakteristík a rezistencie na vysokú teplotu pri tetraploidných genotypoch pšenice (Triticum L.)

The collection of 10 parental lines of tetraploid wheat genotypes with various origin was cultivated in growth chamber. Leaf and growth traits such as assimilation pigments content, dry mass and leaf area of plants were measured. The genotype differences were recognized by chlorophyll a fluorescence fast kinetics method applied on penultimate young wheat leaves. Consequently, heat stress susceptibility based on the exposure of whole plants in pots to air temperature of 42oC for 6 hours was measured, too. Rapid chlorophyll a fluorescence kinetics method gave us better knowledge about differences among tetraploid wheat genotypes collection comparing to classic assimilation pigments analyse. Genotypes with higher content of pigments did not always exhibit good resistance against heat stress. Using the chlorophyll fluorescence parameters, the rating of genotypes based on photosynthetic performance as well as photosystem II (PSII) thermostability was done. We identified the genotypes TRG7 (Triticum turgidum subsp. turgidum, PI 384230, Ethiopia) and RONCAL (Triticum turgidum subsp. dicoccon, TRI 17700, Spain) as the perspective donors of genes for better thermostability of photosynthetic apparatus in changed climate conditions and material into wheat efficiency breeding programs.

Effects of root temperature on thermostability of photosynthetic apparatus in Prunus mira seedlings.

Effects of root temperature on thermostability of photosynthetic apparatus in Prunus mira seedlings.

Overexpression of Sweet Pepper Glycerol‐3‐Phosphate Acyltransferase Gene Enhanced Thermotolerance of Photosynthetic Apparatus in Transgenic Tobacco

In order to investigate the relationship between the lipid composition in thylakoid membrane and thermostability of photosynthetic apparatus, tobacco transformed with sweet pepper sense glycerol-3-phosphate acyltransferase (GPAT) gene were used to analyze the lipid composition in thylakoid membrane, the net photosynthetic rate and chlorophyll fluorescence parameters under high temperature stress. The results showed that the saturated extent of monogalactosyldiacylglycerol (MGDG), sulfoquinovosyldiacylglycerol, digalactosyldiacylglycerol and phosphatidylglycerol in thylakoid membrane of transgenic tobacco T(1) lines increased generally. Particularly, the saturated extent in MGDG increased obviously by 16.2% and 12.0% in T(1)-2 and T(1)-1, respectively. With stress temperature elevating, the maximum efficiency of photosystem II (PSII) photochemistry (Fv/Fm), actual photochemical efficiency of PSII in the light (Phi(PSII)) and net photosynthetic rate (Pn) of the two lines and wild type tobacco plants decreased gradually, but those parameters decreased much less in transgenic plants. Even though the recovery process appeared differently in the donor and acceptor side of PSII in transgenic tobacco compared with wild-type plants, the entire capability of PSII recovered faster in transgenic tobacco, which was shown in the parameters of PI, Fv/Fm and Phi(PSII), as a result, the recovery of Pn was accelerated. Conclusively, we proposed that the increase in saturated extent of thylakoid membrane lipids in transgenic plants enhanced the stability of photosynthetic apparatus under high temperature stress.

Thermostability of photosynthesis in two new chlorophyllb-less rice mutants

Leaves of the two new chlorophyll b-less rice mutants VG28-1, VG30-5 and the wild type rice cv. Zhonghua 11 were subjected to temperatures 28, 36, 40, 44 and 48 degrees C in the dark for 30 min or gradually elevated temperature from 30 degrees C to 80 degrees C at 0.5 degrees C/min. The thermostability of photosynthetic apparatus was estimated by the changes in chlorophyll fluorescence parameters, photosynthetic rate and pigment content, chloroplast ultrastructure and tissue location of H2O2 accumulation. There were different patterns of F(o)-temperature curves between the Chl b-less mutants and the wild type plant, and the temperature of F(o) rising threshold was shifted 3 degrees C lower in the Chl b-less mutants (48 degrees C) than in the wild type (51 degrees C). At temperature up to about 45 degrees C, chloroplasts were swollen and thylakoid grana became misty accompanied with the complete loss of photosynthetic oxygen evolution in the two Chl b-less mutants, but chloroplast ultrastructure in the wild type showed no obvious alteration. After 55 degrees C exposure, the disordered thylakoid and significant H2O2 accumulation in leaves were found in the two Chl b-less mutants, whereas in the wild type plant, less H2O2 was accumulated and the swollen thylakoid still maintained a certain extent of stacking. A large extent of the changes in qP, NPQ and Fv/Fm was consistent with the Pn decreasing rate in the Chl b-less mutants during high temperature treatment as compared with the wild type. The results indicated that the Chl b-less mutants showed a tendency for higher thermosensitivity, and loss of Chl b in LHC II could lead to less thermostability of PSII structure and function. Heat damage to photosynthetic apparatus might be partially attributed to the internal oxidative stress produced at severely high temperature.