We studied photosynthetic capacity, growth, sap flow, and water-use efficiency in young trees of ‘Pink Lady’ apple (Malus domestica) that were exposed to 60 d of moisture stress. Three irrigation schemes were tested in the greenhouse: well-watered control; drought; or alternate deficit irrigation (ADI). Compared with the drought-stressed plants, those treated via ADI showed better height growth, larger scion diameters, and greater total leaf area, as well as significantly increased gains in dry biomass and rootstock diameters. However, their performance was still significantly lower than that demonstrated by continuously well-watered plants. Sap flow was greater under ADI than under drought, but less than under control conditions. The average rate of net photosynthesis, total amount of irrigation water applied, and dry biomass gain had highly significant and positive linear correlations with long-term water-use efficiency (WUEL). The same was true between average stomatal conductance and WUEL. By contrast, instantaneous water-use efficiency (WUEI) was very significantly and negatively correlated with WUEL. In addition, values for WUEL were much higher from well-watered plants when compared with either drought-stressed trees or those treated per ADI. Therefore, our results indicate that, although ‘Pink Lady’ apple normally has high WUE, it still consumes a large amount of water. Therefore, the practice of ADI following a period of long-term drought could be used to improve growth and WUEL by this cultivar., X. P. Sun ... [et al.]., and Obsahuje bibliografii
The effects of ambient levels of ozone and summer drought were assessed on a poplar clone (Populus maximowiczii Henry X P. × berolinensis Dippel - Oxford clone) in an open top chamber experiment carried out at the Curno facilities (Northern Italy). Chlorophyll (Chl) a fluorescence parameters (from both modulated and direct fluorescence) were assessed at different hours of the day (predawn, morning, midday, afternoon, and evening), from June to August 2008. This paper compares the results from predawn (PD, before sunrise) and afternoon (AN, in full sunlight) measurements, in order to evaluate the role of high sunlight as a factor influencing responses to ozone stress. Sunlight affected the maximum quantum yield of primary photochemistry (decrease of Fv/Fm) thus indicating photoinhibition. The effective quantum yield (ΦPSII) and the photochemical quenching (qP) were enhanced in the afternoon with respect to the predawn, whereas the nonphotochemical quenching (NPQ) was reduced. The effect of ozone was detected with fluorescence on well watered plants in the first week of July, before the onset of visible symptoms. As far as Fv/Fm are concerned, the differences between ozone-treated and control plants were statistically significant in the predawn, but not in the afternoon. Ozone exerted only minor effects on drought exposed plants because of the reduced stomatal ozone uptake, but effects on the IP phase of the fluorescence transient were observed also in drought-stressed plants., R. Desotgiu ... [et al.]., and Obsahuje bibliografii
Hvězdoše patří k nejběžnějším a přitom nejvíce přehlíženým vodním rostlinám naší květeny. Jsou charakterizovány na jedné straně celkovou redukcí tělní stavby, na druhé straně vysokou měrou fenotypové plasticity – schopností pružně reagovat na změny prostředí změnou habitu. Kvůli těmto vlastnostem patří hvězdoše mezi determinačně obtížné skupiny. Překvapivě však existuje u hvězdošů pozoruhodné množství různých opylovacích způsobů: dokáží se opylovat na vzduchu, po vodní hladině i pod vodou. Kombinace všech těchto tří způsobů opylení není známa u žádných jiných rostlin. Všechny opylovací systémy se pak u hvězdošů kombinují s ojedinělými a kuriózními způsoby samoopylení., Water-starworts (Callitriche) are some of the most common and yet largely overlooked aquatic plants in European flora. They are characterized by overall reduction of the plant body and also exhibit an extraordinary phenotypic plasticity in response to environmental changes, which makes the starwort species very difficult to determine. It is the only genus known to possess all three types of pollination: by air, on the water surface and under water, in addition to some unique self-fertilization mechanisms., and Jan Prančl.
Carnivorous plants grow in nutrient-poor habitats and obtain substantial amount of nitrogen from prey. Specialization toward carnivory may decrease the ability to utilize soil-derived sources of nutrients in some species. However, no such information exists for pitcher plants of the genus Nepenthes, nor the effect of nutrient uptake via the roots on photosynthesis in carnivorous plants is known. The principal aim of present study was to investigate, whether improved soil nutrient status increases photosynthetic efficiency in prey-deprived pitcher plant Nepenthes talangensis. Gas exchange and chlorophyll (Chl) fluorescence were measured simultaneously and were correlated with Chl and nitrogen concentration as well as with stable carbon isotope abundance (δ13C) in control and fertilized N. talangensis plants. Net photosynthetic rate (PN) and maximum- (Fv/Fm) and effective quantum yield of photosystem II (ΦPSII) were greater in the plants supplied with nutrients. Biomass, leaf nitrogen, and Chl (a+b) also increased in fertilized plants. In contrast, δ13C did not differ significantly between treatments indicating that intercellular concentration of CO2 did not change. We can conclude that increased root nutrient uptake enhanced photosynthetic efficiency in prey-deprived N. talangensis plants. Thus, the roots of Nepenthes plants are functional and can obtain a substantial amount of nitrogen from the soil. and A. Pavlovič ... [et al.].
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.