Botanická zahrada v Rio de Janeiru je zajímavým východiskem k pozorování bromeliovitých rostlin. Nachází se v oblasti obzvláště bohaté na zástupce čeledi Bromeliaceae. Zvláštní kapitola je věnována robustním druhům rodu Alcantarea a jejich ekologii. Je zmíněn slavný zahradní architekt Roberto Burle Marx, který uvedl druh Alcantarea imperialis do svých věhlasných zahradních aranžmá., The Botanical Garden of Rio de Janeiro is an interesting starting point for observation of bromeliads. It is located in an area particularly rich in species of the family Bromeliaceae. An emphasis is given to robust species of the genus Alcantarea and their ecology. Roberto Burle Marx, a famous garden and park designer, is mentioned because he introduced the species A. imperialis in his well-known garden arrangements., and Miloslav Studnička.
Nowadays, a quest for efficient greenhouse heating strategies, and their related effects on the plant's performance, exists. In this study, the effects of a combination of warm days and cool nights in autumn and spring on the photosynthetic activity and efficiency of Phalaenopsis were evaluated; the latter, being poorly characterised in plants with crassulacean acid metabolism (CAM) and, to our knowledge, not reported before in Phalaenopsis. 24-h CO2 flux measurements and chlorophyll (Chl) fluorescence analyses were performed in both seasons on Phalaenopsis 'Hercules' exposed to relatively constant temperature regimes, 25.5/24.0°C (autumn) and 30/27°C (spring) respectively, and distinctive warm day/cool night temperature regimes, 27/20°C (autumn) and 36/24°C (spring), respectively. Cumulated leaf net CO2 uptake of the distinctive warm day/cool night temperature regimes declined with 10-16% as compared to the more constant temperature regimes, while the efficiency of carbon fixation revealed no substantial differences in both seasons. Nevertheless, a distinctive warm day/cool night temperature regime seemed to induce photorespiration. Although photorespiration is expected not to occur in CAM, the suppression of the leaf net CO2 exchange during Phase II and Phase IV as well as the slightly lower efficiency of carbon fixation for the distinctive warm day/cool night temperature regimes confirms the involvement of photorespiration in CAM. A seasonal effect was reflected in the leaf net CO2 exchange rate with considerably higher rates in spring. In addition, sufficiently high levels of photosynthetically active radiation (PAR) in spring led to an efficiency of carbon fixation of 1.06-1.27% which is about twice as high than in autumn. As a result, only in the case where a net energy reduction between the temperature regimes compensates for the reduction in net CO2 uptake, warm day/cool night temperature regimes may be recommended as a practical sustainable alternative. and B. Pollet ... [et al.].
Salinization and alkalization of soil are widespread environmental problem and the alkali stress is more destructive than the effects caused by salt stress. To compare the mechanism of salt and alkali stresses, a sunflower variety (Helianthus annuus L. cv. Baikuiza 6) was tested under saline or alkaline conditions by mixing two neutral salts (NaCl and Na2SO4) or two alkaline salts (NaHCO3 and Na2CO3). The results showed that saline conditions differed greatly from alkaline conditions in their threshold intensities where sunflower can germinate, survive and grow. Under saline conditions, the emergence time was delayed, and the emergence rate and seedling survival rate also decreased with increasing salinity. However, under alkaline conditions, the rate of seedling survival decreased sharply but the emergence time and emergence rate did not change. In addition, the damaging effects of alkali stress on growth and photosynthesis were more severe than those of saline. In shoots, the main inorganic osmolyte and cation was K+ rather than Na+; the primary organic osmolytes were organic acid and soluble sugar rather than proline. Organic acid, NO3 -, and Cl- (only under saline condition) were the main source of anion. In addition, the osmotic adjustment and ion balance differed among sunflower roots, stems, and leaves. In conclusion, saline and alkaline conditions are two different stress conditions and there are special responses to two stress conditions for sunflower. and J. Liu, W. Q. Guo, D. C. Shi.
Physiological responses of two duckweed species, Lemna gibba and Lemna minor, to hexavalent chromium [Cr(VI)] were studied in axenic cultures using short-term (48 h) treatments by K2Cr2O7 (0-200 μM). Chlorophyll (Chl) fluorescence parameters and photosynthetic pigment composition of plants were screened to determine the effects of Cr(VI) exposures. The two duckweed species exhibited different sensitivity in the applied Cr(VI) concentration range. Chl fluorescence parameters of dark-adapted and light-adapted plants and electron transport inducibility were more sensitive to Cr(VI) in L. minor than in L. gibba. We also found fundamental differences in quantum yield of regulated, Y(NPQ), and nonregulated, Y(NO), non-photochemical quenching between the two species. As Cr(VI) concentration increased in the growth medium, L. minor responded with considerable increase of Y(NPQ) with a parallel significant increase of Y(NO). By contrast, in L. gibba only 200 μM Cr(VI) in the growth medium resulted in elevation of Y(NPQ) while Y(NO) remained more or less constant within the regarding Cr(VI) concentration range during 48 h. Photosynthetic pigment content did not change considerably during the short-term Cr(VI) treatment but decrease of Chl a/b and increase of Car/Chl ratios were observed in good accordance with the changes in Chl fluorescence parameters. The data suggest that various duckweed species respond with different sensitivity to the same ambient concentrations of Cr(VI) in the growth medium, and presumably to other environmental stresses too, which may have an influence on their competitive relations when heavy metal pollution occurs in aquatic ecosystem. and V. Oláh ... [et al.].
Molekulární metody umožnily studovat šíření rostlin v povodí Labe. Druhy šířené vodou (zevar, stulík) migrují především jednosměrně podél řek. Bylo prokázáno i šíření mezi říčními systémy, častější je u druhů šířících se také větrem (rákos, orobinec). Klonální šíření mezi populacemi není u těchto studovaných druhů rostlin tak běžné, jak se dosud předpokládalo., Molecular approaches have allowed for the study of plant dispersal in the catchment area of the River Elbe. Plants dispersed by water (Bur-reed, Pond Lily) migrated mainly unidirectionally along streams. Dispersal among river systems was also detected and is more common among plants with wind dispersal (Common Reed, Cattail). Clonal dispersal does not seem to be as common in the studied species as previously suggested., and Tomáš Fér.
In this paper, photosynthetic characteristics of green leaves (GL) and green pseudobulbs (GPSB) of C3 orchid Oncidium Golden Wish were first studied. Light saturation for photosynthesis and maximum photosynthetic rates (Pmax) were significantly higher in GL than in GPSB. The results of the optimal PSII quantum yield (Fv/Fm ratio), electron transport rate (ETR), the effective photochemical quantum yield (ΔF/Fm') and nonphotochemical quenching (NPQ) of Chl fluorescence revealed that GPSB had lower light utilization than that of GL. Significantly higher photosynthetic pigments were found in GL than in GPSB. Alteration of source/sink ratio had no impact on all photosynthetic parameters for both GL and GPSB after a short term of 3 days or even a long term of 2 weeks of treatments although there were significant decreases in GL carbohydrate concentration of GL-darkened plants by the end of the day. However, decreases of all photosynthetic parameters of GL were observed in GL-darkened plants after 4 weeks of treatment compared to those of fully illuminated (FI) and GPSB-darkened plants. These results indicate that the level of carbohydrates in GL plays an important role in regulating their photosynthesis. Due to their lower photosynthetic capacities, GPSB function mainly as sinks. Darkening GPSB up to 2 weeks did not affect their own Pmax and the Pmax of GL and thus, did not result in significant decreases of total carbohydrate concentration of GPSB. As GPSB store a large amount of carbohydrates, it could also act as a source when the level of carbohydrates decreased. Thus, GL could depend on GPSB carbohydrates to regulate their photosynthesis when their source capacity was removed. However, 4 weeks after treatments, photosynthetic capacities of GL were significantly lower in GL- and GPSB-darkened plants than in FI plants, which could be due to the lower total soluble and insoluble sugar concentrations of both GL and GPSB in these plants. and J. He, B. H. G. Tan, L. Qin.
Spatial and temporal variations in light-saturated photosynthetic capacity and needle nitrogen (N) content were investigated in one
8 m tall Japanese cedar (Cryptomeria japonica D. Don) canopy for a full year. The photosynthetic capacity and needle N content in various layers of the canopy were measured every month. Temporal variations in photosynthetic capacity and needle N content expressed on a projected-area basis (Parea, Narea) were similar. Furthermore, both Parea and Narea decreased with increasing depth from the top of the canopy on each sampling date. As a consequence, a significant correlation was observed between Narea and Parea. Temporal variations in photosynthetic capacity and needle N content expressed on a mass basis (Pmass, Nmass) were also similar. Pmass also decreased with increasing canopy depth. However, in contrast to Narea, there was only a slight decrease in Nmass with increasing canopy depth. Hence, the correlation between Nmass and Pmass was lower than the projected-area value. Because Narea was highly correlated with the needle mass per projected-area (NMA), the spatial variation in Narea (and therefore Parea) in the canopy is attributed to the variation in NMA, which decreases as the depth from the top of the canopy increases. Furthermore, the slope of the linear regression between Narea and NMA differed between sampling dates, indicating that the temporal variations in Narea (and therefore Parea) are strongly influenced by Nmass. For most of the sampling dates, a linear regression between Narea and Parea tends to converge into a single line segment. However, on several sampling dates, there was a pronounced decline in Parea below this line segment. This reduction in Parea, which does not accompany a reduction in Narea, seems to be attributable to stomatal limitations induced by the low soil temperature in winter and early spring. and H. Kobayashi, S. Inoue, K. Gyokusen
The specificity factor of Rubisco (S f) was estimated in intact leaves from the carboxylation of ribulose-1,5-bisphosphate (RuBP) at various CO2/O2 ratios. As oxygenation is calculated by the difference of the 14CO2 uptake by RuBP in the absence and presence of oxygen, it is important to choose the optimum CO2/O2 ratios. At high CO2 concentration (1,000 cm3 m-3 and higher) oxygenation consumes less than 50% RuBP but the difference of concentrations of CO2 at cell walls (Cw) and at the carboxylation centers (Cc) is 2-5% and the influence of mesophyll resistance
(rmd) is of minor importance. To accumulate large endogenous pool of RuBP, the leaves were preilluminated in the CO2- and
O2-free gas environments for 8 to 10 s. Thereafter the light was switched off and the leaves were flushed with the gas containing different concentrations of 14CO2 and O2. The specificity factor of Rubisco was calculated from the amount of the tracer taken up under different 14CO2/O2 ratios by the exhaustion of the RuBP pool. Application of 14CO2 allowed us to discriminate between the CO2 uptake and the concurrent respiratory CO2 release which proceeded at the expense of unlabelled intermediates., J. Viil, H. Ivanova, T. Pärnik., and Obsahuje bibliografii
The mechanisms of capsicum growth in response to differential light availabilities are still not well elucidated. Hereby, we analyzed differential light availabilities on the relationship between stomatal characters and leaf growth, as well as photosynthetic performance. We used either 450-500 µmol m-2 s-1 as high light (HL) or 80-100 µmol m-2 s-1 as low light (LL) as treatments for two different cultivars. Our results showed that the stomatal density (SD) and stomatal index (SI) increased along with the leaf area expansion until the peak of the correlation curve, and then decreased. SD and SI were lower under the LL condition after three days of leaf expansion. For both cultivars, downregulation of photosynthesis and electron transport components was observed in LL-grown plants as indicated by lower light- and CO2-saturated photosynthetic rate (Pmax and RuBPmax), quantum efficiency of photosystem II (PSII) photochemistry (ΦPSII), electron transport rate (ETR) and photochemical quenching of fluorescence (qp). The observed inhibition of the photosynthesis could be explained by the decrease of SD, SI, Rubisco content and by the changes of the chloroplast. The low light resulted in lower total biomass, root/shoot ratio, and the thickness of the leaf decreased. However, the specific leaf area (SLA) and the content of leaf pigments were higher in
LL-treatment. Variations in the photosynthetic characteristics of capsicum grown under different light conditions reflected the physiological adaptations to the changing light environments. and Q. S. Fu ... [et al.].