The altitudinal effects on photosynthesis were measured on progenies of three populations of Rosa platyacantha Schrenk from altitudes of 1,170 (L); 1,580 (M); and 1,920 (H) m a. s. l. During the day, net photosynthetic rate (PN) decreased in all populations due to the high air temperature in the summer. The H population showed a significantly lower PN at noon compared to other populations. The midday depression of PN occurred in L and M populations due to stomatal limitations, while PN inhibition was associated with PSII activity decline in the H population. In order to avoid photodamage, the plants of H population triggered active antioxidant defenses with a higher enzyme activity and redox ratio of ascorbate at midday compared to the L and M populations. However, more oxidative injury still occurred in the H plants at noon due to higher lipid peroxidation. Our results indicated that the provenance significantly affected photosynthesis in R. platyacantha from northwestern China., S. H. Yang, J. J. Wei, H. Ge., and Obsahuje bibliografii
Photoinhibition is a significant constraint for improvement of radiation-use efficiency and yield potential in cereal crops. In this work, attached fully expanded leaves of seedlings were used to assay the factors determining photoinhibition and for evaluation of tolerance to photoinhibition in wheat (Triticum aestivum L.). Our results showed that even 1 h under PPFD of 600 µmol(photon) m-2 s-1 could significantly reduce maximal quantum yield of PSII photochemistry (Fv/Fm) and performance index (PI) compared to low light [300 µmol(photon) m-2 s-1]. The decrease of Fv/Fm and PI was more noticeable with the increase of light intensity; irradiance higher than 800 µmol(photon) m-2 s-1 resulted in photoinhibition. Compared to 25°C, lower (20°C) or higher temperature (≥ 35°C) aggravated photoinhibition, while slightly high temperature (28°) alleviated photoinhibition. At 25°C, irradiance of 1,000 µmol(photon) m-2 s-1 for 1 h was enough to cause photoinhibition and a significant decrease of Fv/Fm, PI, trapped energy flux, electron transport flux, and density of reaction center as well as increase of dissipated energy flux per cross section were observed. In addition, seedlings at 21-32 days after planting showed a relatively stable phenotype, while the younger or older seedlings indicated an increased susceptibility to photoinhibition, especially in senescing leaves. Finally, six wheat varieties with relative tolerance to photoinhibition were identified from 22 Chinese winter wheat varieties by exposing attached leaves of the 25-d old seedlings for 1 h to 1,000 µmol(photon) m-2 s-1 at 25°C. Therefore, our work established a possible method for development of new wheat varieties with enhanced tolerance to photoinhibition., H. Li, Q. Zheng, J. Zhang, B. Li, Z. Li., and Obsahuje bibliografii
The antenna sizes of QB-reducing photosystem 2 (PS2) complexes in two different fractions of the subchloroplast particles were compared by measuring time corresponding to the second maximum of the first derivative from induction curve of chlorophyll fluorescence as a function of actinic irradiance. The QB-reducing PS2 complexes in the fraction of particles that originated from inner parts of grana thylakoids had smaller antennae than those in the fraction from non-appressed regions of thylakoid membranes.
Chlorophyll (Chl) fluorescence from greening and fiilly green barley leaves was analyzed using a phase-modulated fluorimeter. Inunediately following the irradiation of fiilly-etiolated leaves, a pool of (newly-synthesised) Chl/chlorophyllide was detected with a fluorescence lífetime similar to that of these pigments in solution. After some hours, the major fluorescence component was a short-lifetime species which we believe to represent photosystem 2. Selective inhibition of polypeptide synthesis in either the chloroplast or cytosol greatly reduced the extent of Chl assimilation and gave rise to novel fluorescence-lifetime profiles which are believed to arise flom complexes in various stages of assembly. Hence angiosperms háve evolved control systems to lim't the appearance of free Chl; this involves close co- ordination between pigment and polypeptide synthesis.
C4 photosynthetic pathway and life form were determined for 159 species in 71 genera and 13 families in the grassland of North China. 45 % of the C4 species were found in Graminae, 19 % in each of Cyperaceae and Chenopodiaceae. More than 51 % of these C4 species were in therophyta and 36 % hemicryptophyta, while fewer species were in nanophanerophyta (9 %) or geophyta (5 %). The numbers of C4 species and their life forms were closely related with grassland deterioration and succession in North China. This indicated that the C4 species had greater capacity to tolerate environmental stress (e.g. drought and salinity) caused by animal grazing and cultivation.
To explore the cause of difference in photosynthetic performance between different cultivars of crops, leaf net photosynt rate (PN) and photosystem 2 (PS2) photochemical efficiency (Fv/Fm), apparent quantum yield of carbon assimilation (φc), electron transport rate, photophosphorylation activity, etc. were measured in two soybean cultivars, Heinong 42 and Heinong 37. At pod setting and filling, significant differences in PN between them were observed. The former with a higher PN (from 7 to 38 %) had a significantly higher leaf thickness, leaf dry mass/area (LMA), chlorophyll content, soluble protein content, apparent quantum yield of electron transport through PS2 (φe), carboxylation efficiency (CE), and ribulose-1,5-bisphosphate carboxylase (RuBPC) activity. The significantly higher PN of Heinong 42 is mainly due to its higher content and activity of RuBPC. and Hua Jiang, Da-Quan Xu.
Genetic analysis of the content of light-harvesting complexes of thylakoid membranes was accomplished for the first time during the study of intraspecific variation in photosynthetic characteristics. The existence of genetically determined differences between genotypes together with positive heterosis in F1 generation was demonstrated.
We identified and characterised the deep red state (DRS), an optically-absorbing charge transfer state of PSII, which lies at lower energy than P680, in the red algae Cyanidioschyzon merolae by means of low temperature absorption and magnetic circular dichroism spectroscopies. The photoactive DRS has been previously studied in PSII of the higher plant Spinacia oleracea, and in the cyanobacterium Thermosynechococcus vulcanus. We found the DRS in PSII of C. merolae has similar spectral properties. Treatment of PSII with dithionite leads to reduction of cytochrome (cyt) b559 and the PsbV-based cyt c550 as well as the disassembly of the oxygen-evolving complex. Whereas the overall visible absorption spectrum of PSII was little affected, the DRS absorption in the reduced sample was no longer seen. This bleaching of the DRS is discussed in terms of a corresponding lack of a DRS feature in D1D2/cyt b559 reaction centre preparations of PSII., J. Langley, J. Morton, R. Purchase, L. Tian, L. Shen, G. Han, J.-R. Shen, E. Krausz., and Obsahuje bibliografické odkazy
Advances achieved during last fifteen years in the understanding the development of chloroplast ultrastructure during natural leaf ontogeny are summarized. Life span of a typical C3 mesophyll cell chloroplast is outlined and placed into the scheme of cyclic plastid interrelationships. Possible modifications of this development by stresses, environmental factors or experimental treatments are also shown.