C4 photosynthetic pathway and morphological functional types were determined for 104 species in 45 genera and 10 families from the deserts of China. 67 C4 species (64.4 %) were found in Dicotyledoneae (e.g. Chenopodiaceae, Polygonaceae, and Amaranthaceae), the other 37 species were in Monocotyledoneae (e.g. Gramineae, Cyperaceae, and Commelinaceae). 36.5 % of the Chenopodiaceae species (predominantly members of the genera Anabasis, Atriplex, Kochia, Salsola, and Suaeda) identified in the desert regions were found with C4 photosynthesis, which was about 48 % of the total C4 species. Many C4 species (58.7 %) were annuals (e.g. Amaranthus, Atriplex, Digitaria, Eragrostis, Kochia, and Salsola) and experienced long-term droughts, high temperature, and high irradiance. Relatively more shrub C4 species (28 species of 104) were found in Chenopodiaceae (e.g. Anabasis, Camphorosma, Haloxylon, and Salsola) and Polygonaceae (e.g. Calligonum) in the desert regions. Most of shrub C4 species with small leaf area were no more than 1 m in height and distributed in sandy soils. Composition of relatively more annual species, shrubs, and Chenopodiaceae C4 species was the primary characteristic for the C4 species occurrence in deserts, and this was remarkably related with the arid environmental conditions.
Floristic composition, life forms for C4 species, and the pattern of altitude distribution were studied on Tibetan Plateau. 79 species, in 7 families and 46 genera, were identified with C4 photosynthesis. 95 % of these C4 species belong to Gramineae (51 species), Cyperaceae (14 species), and Chenopodiaceae (10 species), indicating that C4 plants mainly occur in very few families (7 of 204) on the Tibetan Plateau. High altitude distribution for all the Chenopodiaceae C4 species (> 3 000 m above sea level) suggests that plants of this kind have large tolerance to cold, dryness, and strong ultraviolet radiation. Most Gramineae and Cyperaceae C4 species occurrences are consistent with extensive distribution of steppes and meadows in the vast flat of the central Plateau (1 000-3 000 m a.s.l.). Relatively high amount of hemicryptophyte form plants (44 %) in the region indicates that the vegetation, especially grassland, meadows, and steppe, are in good condition. There is a strong relationship between numbers of C4 species and altitude in the Tibetan Plateau. Occurrence of C4 species is significantly less in both high and low altitude plateaux in Tibet. Altitude distribution pattern for C4 species in the region is not only consistent with the altitude and climate, but also with the vegetation types in altitude gradient.
Natural occurrence of C4 species, life forms, and their longitudinal distribution patterns along the Northeast China Transect (NECT) were studied. Six vegetation regions experiencing similar irradiation regimes, but differing in longitude, precipitation, and altitude were selected along the NECT from 108 to 131 °E, around altitude of 43.5 °N. Seventy C4 species were identified in 41 genera and 13 families. 84 % of the total C4 species were found in four families: Gramineae (38 species), Chenopodiaceae (11 species), Cyperaceae (5 species), and Amaranthaceae (5 species). C4 grasses make up 54 % of the total identified C4 species along the NECT and form the leading C4 family in meadow, steppe, and desert along the NECT. C4Chenopodiaceae species make up about 16 % of the C4 species and become less important, particularly in the meadow and the eastern end of the NECT. 57 % of the total C4 species are therophytes and 37 % are hemicryptophytes, which is consistent with floristic composition and land utilization. In general, the number of C4 species decreased significantly from the west to the east or from dry to moist areas along the NECT, and was remarkably correlated with annual precipitation (r2= 0.677) and aridity (r2= 0.912), except for salinized meadow region. The proportion of C4 species from all the six vegetation regions was considerably correlated with these two climatic parameters (r2= 0.626 or 0.706, respectively). These findings suggest that the natural occurrence of C4 species varies significantly along the large-scale longitudinal gradient of the NECT. The notable relationship of C4 species number and proportion in the flora with variations in annual precipitation and aridity suggest that these two climatic parameters are the main factors controlling the longitudinal distribution patterns of C4 species along the NECT.
Plants of Indian mustard (Brassica juncea) were treated with either 50 µM Cd, 250 µM Zn, or 25 µM Cd+125 µM Zn and the progression of chlorosis in the mature leaves monitored. As relative chlorophyll (Chl) contents in the mature leaves decreased to 75, 50, and 25 % relative to controls, both mature and young leaves were harvested and the Chl pools extracted. The metal treatments caused a greater loss of Chl b than Chl a. As mature leaves underwent progressive chlorosis, the young leaves displayed a characteristic over-greening, due largely to increased content of Chl b. However, as the young leaves began to experience chlorosis, a greater loss of Chl b was also observed. Thus during metal induced chlorosis, there is a preferential turnover of the Chl b pool in mature and young leaves. and S. Ebbs, S. Uchil.
The ultrastructure of cells of ground meristem in the peripheral zone of shoot apical meristem in Elodea canadensis Rich. was studied after treatment with cadmium in concentrations 0.5, 1, 2, 3, 5, and 6 g(Cd2+) m-3. After 5 d treatment, changes in the structural organisation of the plastid apparatus were found, namely in proplastid, amyloplast, and amoeboid stages of plastid development. and D. Stoyanova, E. Tchakalova.
In order to understand better Cd resistance in soybean, Dongying wild soybean treated with different Cd concentrations were evaluated. The biomass, chlorophyll (Chl) content, leaf color, Chl a fluorescence parameters, photosynthesis parameters, and Cd contents were determined. Our results showed that when Cd concentration was ≤ 2 kg m-3, no significant decrease in biomass, photosynthetic parameters, and maximal photochemical efficiency of PSII was observed. This indicated that Dongying wild soybean resisted Cd toxic effects under such conditions. In addition, atomic absorption experiment results demonstrated that when Cd concentration was ≤ 0.5 kg m-3, the accumulation of Cd in wild soybean was lower in roots than that in shoots, while the accumulation of Cd was higher in roots than that in shoots when Cd concentration was ≥ 1 kg m-3. Therefore, Dongying wild soybean showed a certain resistance to Cd and could serve as a valuable germplasm resource for improving the breeding of
Cd-resistant soybean., L. Liu, Y. K. Shang, L. Li, Y. H. Chen, Z. Z. Qin, L. J. Zhou, M. Yuan, C. B. Ding, J. Liu, Y. Huang, R. W. Yang, Y. H. Zhou, J. Q. Liao., and Obsahuje bibliografii
Chlorophyll fluorescence has developed into a well-established noninvasive technique to study photosynthesis and by extension, the physiology of plants and algae. The versatility of the fluorescence analysis has been improved significantly due to advancements in the technology of light sources, detectors, and data handling. This allowed the development of an instrumention that is effective, easy to handle, and affordable. Several of these techniques rely on point measurements. However, the response of plants to environmental stresses is heterogeneous, both spatially and temporally. Beside the nonimaging systems, low- and high-resolution imaging systems have been developed and are in use as real-time, multi-channel fluorometers to investigate heterogeneous patterns of photosynthetic performance of leaves and algae. This review will revise in several paragraphs the current status of chlorophyll fluorescence imaging, in exploring photosynthetic features to evaluate the physiological response of plant organisms in different domains. In the conclusion paragraph, an attempt will be made to answer the question posed in the title., R. Valcke., and Obsahuje bibliografické odkazy