a1_The Pantanal is the largest wetland in the world with extremely high plant and animal diversity, but large areas have been invaded by Vochysia divergens Pohl (Vochysiaceae), a tree that is native to the Amazon Basin, and Curatella americana L. (Dilleniaceae), a tree that is native to the Brazilian savanna (cerrado). V. divergens is reportedly floodadapted, thus its ability to invade the Pantanal may not be surprising, but the invasion of C. americana is counterintuitive, because this species is adapted to the
well-drained soils of the cerrado. Thus, we were interested in comparing the photosynthetic capacity, in terms of CO2 conductance, carboxylation, and electron transport of these species over a seasonal flooding cycle. Given that V. divergens is reportedly flood-adapted, we predicted that this species would have a higher photosynthetic capacity than C. americana, especially under flooding. To test this hypothesis we measured the photosynthetic CO2 response (PN/Cc) of V. divergens and C. americana within 1 year to determine, if photosynthetic capacity varied systematically over time and between species. Contrary to our hypothesis, V. divergens did not always have a higher photosynthetic capacity than C. americana. Rather, species differences were influenced by temporal variations in flooding and the leaf age. Leaf CO2 assimilation and photosynthetic capacity of both species were lower during the flood period, but the differences were not statistically significant. The physiological performance of both species was strongly related to leaf N and P concentrations, but P limitation appeared to be more important than N limitation for these species and ecosystem. Photosynthetic capacity was higher and more stable for V. divergens, but such an advantage did not result in a statistically significant increase in PN., a2_Our results suggest that both species are tolerant to flooding even though they are adapted to very different hydrological conditions. Such physiological plasticity, especially for C. americana, might be a key feature for the ability to survive and persist in the seasonally flooded Pantanal., H. J. Dalmagro ... [et al.]., and Obsahuje bibliografii
In vivo chlorophyll fluorescence analysis reflecting the photosystem II functionality was investigated in the cyanobacterium Anabaena variabilis PCC 7937 under simulated solar radiation in a combination with various cut-off filters (WG 280, WG 295, WG 305, WG 320, WG 335, WG 345, and GG 400) to assess the effects of photosynthetically active radiation (PAR), ultraviolet-A (UV-A), and ultraviolet-B (UV-B) radiations on photosynthesis. The photosynthetic activity (PA) was severely inhibited immediately after 10 min of exposure to high PAR, UV-A, and UV-B radiations compared with low PAR grown control samples. After 1 h of exposure, PA of 17.5 ± 2.9% was detected in the high PAR exposed samples compared with the control, while only a trace or no PA was observed in the presence of ultraviolet radiation (UVR). A recovery of PA was recorded after 2 h of the exposure, which continued for next 4, 8, 12, and 24 h. After 24 h of the exposure, PA of 57.5 ± 1.9%, 36.1 ± 11.7%, 23.5 ± 3.3%, 22.3 ± 5.2%, 20.8 ± 6.7%, 13.2 ± 6.6%, and 21.6 ± 9.5% was observed compared with the control sample in 400, 345, 335, 320, 305, 295, and 280 nm cut-off filters-covered samples, respectively. The relative electron transport rate, measured after 24 h exposure, showed also a disturbance in electron transfer between the two photosystems under the high PAR and UVR treatments relative to the control samples, suggesting the inhibition of photosynthesis. This study suggests that both high PAR and UVR inhibited the photosynthetic performance of A. variabilis PCC 7937 by damaging the photosynthetic apparatus, however, photoprotective mechanisms evolved by the organism allowed an immediate repair of ecologically important machinery, and enabled its survival., S. P. Singh ... [et al.]., and Obsahuje bibliografii
Pulses of rainfall are particularly pivotal in controlling plant physiological processes in ecosystems controlled by limited water, and the response of desert plants to rainfall is a key to understanding the responses of desert ecosystems to global climatic change. We used a portable photosynthesis system to measure the responses of the diurnal course of photosynthesis, light-response curves, and CO2-response curves of two desert shrubs (Nitraria sphaerocarpa Maxim. and Calligonum mongolicum Turcz) to a rainfall pulse in a desert-oasis ecotone in northwestern China. The photosynthetic parameters, light- and CO2-response curves differed significantly before and after the rainfall pulse. Their maximum net photosynthetic rate (PN) values were 23.27 and 32.92 μmol(CO2) m-2 s-1 for N. sphaerocarpa and C. mongolicum, respectively, with corresponding maximum stomatal conductance (gs) values of 0.47 and 0.39 mol(H2O) m-2 s-1. The PN of N. sphaerocarpa after the rainfall was 1.65 to 1.75 times the value before rainfall, whereas those of C. mongolicum increased to approximately 2 times the prerainfall value, demonstrating the importance of the desert plants response by improving their assimilation rate to precipitation patterns under a future climate., B. Liu, W. Z. Zhao, Z. J. Wen., and Obsahuje bibliografii
To explore the effects of water column nutrient loading on photosynthesis of the submerged macrophyte Vallisneria natans (Lour.) Hara during the growth season (June to October), we determined the diurnal and seasonal variation in rapid light curves of plants cultivated under 4 different nutrient concentrations (N-P [mg L-1]: (1) 0.5, 0.05; (2) 1.0, 0.1; (3) 5.0, 0.5; (4) 10.0, 1.0). Nutrient concentration significantly affected the magnitude of the rapid light curves of V. natans, but not the direction of their diurnal variations. At low nutrient conditions (N-P 1 [mg L-1]: 0.5, 0.05), the maximum relative electron transport rate (rETRmax) and minimum saturating irradiance (Ek) derived from rapid light curves were significantly lower than those of other treatments, and their seasonal variations were suppressed. These results indicated that photosynthesis of V. natans was inhibited by the lack of nutrients in water column. At high nutrient conditions (N-P 4, [mg L-1]: 10.0, 1.0), there was an increase in photosynthetic rate in the light-limited region of rapid light curve (α), and a decrease in rETRmax and Ek, relative to moderate nutrient conditions (N-P 2, [mg L-1]: 1.0, 0.1). In addition, at high nutrient concentrations, the rapid light curves of V. natans reached a plateau, and then markedly declined compared with those at the lower nutrient levels, especially in July and August. These results suggested that V. natans were adapted to low-light environments in the high-nutrient loading treatment., X. L. Cai ... [et al.]., and Obsahuje bibliografii
Flooding is common in lowlands and areas with high rainfall or excessive irrigation. A major effect of flooding is the deprivation of O2 in the root zone, which affects several biochemical and morphophysiological plant processes. The objective of this study was to elucidate biochemical and physiological characteristics associated with tolerance to O2 deficiency in two clonal cacao genotypes. The experiment was conducted in a greenhouse with two contrasting clones differing in flood tolerance: TSA-792 (tolerant) and TSH-774 (susceptible). Leaf gas exchange, chlorophyll (Chl) fluorescence, chemical composition and oxidative stress were assessed during 40 d for control and flooded plants. Flooding induced a decrease in net photosynthesis, stomatal conductance and transpiration of both genotypes. In flood conditions, the flood-susceptible clone showed changes in chlorophyll fluorescence, reductions in chlorophyll content and increased activity of peroxidase and polyphenol oxidase. Flooding also caused changes in macro- and micronutrients, total soluble sugars and starch concentrations in different plant organs of both genotypes. Response curves for the relationship between photosynthetically active radiation (PAR) and net photosynthetic rate (PN) for flooded plants were similar for both genotypes. In flood conditions, the flood-susceptible clone exhibited (1) nonstomatal limitations to photosynthesis since decreased in maximum potential quantum yield of PSII (Fv/Fm) values indicated possible damage to the PSII light-harvesting complex; (2) oxidative stress; (3) increased leaf chlorosis; and (4) a reduction in root carbohydrate levels. These stresses resulted in death of several plants after 30 d of flooding., F. Z. Bertolde ... [et al.]., and Obsahuje bibliografii
Morphological and physiological traits of Crepis pygmaea L. subsp. pygmaea and Isatis apennina Ten. ex Grande growing at different altitudes in the Gran Sasso Massif (Abruzzo, Italy) were analyzed. The two populations of C. pygmaea and I. apennina growing at the highest altitude (Cp2 and Ip2 at 2,310 m a.s.l. and 2,350 m a.s.l., respectively) had a lower leaf mass area (LMA) than the two populations growing at the lowest altitude (Cp1 and Ip1 at 2,250 m a.s.l. and 2,310 m a.s.l., respectively). Leaf tissue density (LTD) had the same LMA trend, decreasing 23 and 10% in C. pygmaea and I. apennina, respectively, from the highest to the lowest altitude. C. pygmaea and I. apennina had the highest photosynthetic rates
(PN) in July decreasing on an average 17 and 30%, respectively, in August and 50 and 38%, respectively, in September. Leaf respiration (R) in Ip1 and Ip2 had the same trend as Cp1 and Cp2, showing the highest rates in September. Global warming could drive C. pygmaea and I. apennina toward higher altitudes in the Gran Sasso Massif. Nevertheless, C. pygmaea with the higher plasticity index (PI) both at physiological and at morphological levels (0.50 and 0.35, respectively) might have a competitive advantage over I. apennina over the long term., L. Gratani ... [et al.]., and Obsahuje bibliografii
a1_The study of plant responses to environmental stress factors is essential for management of plant systems and for anticipating their response to climate change. The main goal of this study was to determine morphological and physiological responses of Nothofagus obliqua and N. nervosa seedlings to light and temperature, two of the main stress factors acting in their current natural distribution in NW Patagonia. Responses to light were evaluated analyzing growth and survival, as well as morphological and physiological traits related to them, in seedlings subjected to three contrasting light conditions (full-sun conditions, 50% of sunlight and 20% of sunlight) during one growth season. Temperature photosynthetic responses were evaluated in seedlings subjected to temperature treatments between -5 and 40°C for 2 and 4 h. Growth rate and biomass partition were similar between light treatments in both species. High apical meristem damage and decreased photosynthetic capacity of preformed leaves were observed under full-sun conditions, suggesting that high light levels have a deleterious effect on plant yield. Both species produced neoformed leaves during the growing season with better photosynthetic capacity than preformed leaves under full sun conditions, contributing to plant acclimation. Almost no plasticity was observed in morphological traits in response to shade. Both species differed in optimum temperature for photosynthesis, with a wider temperature range at which high photosynthesis is maintained in N. obliqua. In both species the higher values of net photosynthetic rate were found at higher temperatures than the mean annual temperature of its current natural distribution range., a2_Under no water-stress conditions, future higher temperatures could increase carbon fixation of these species, with a little advantage of N. obliqua if temperature variance is high. Synergy effect of various environmental stress factors, particularly considering cultivation of these species outside their current natural distribution sites require further studies., S. A. Varela ... [et al.]., and Obsahuje bibliografii
podává Norbert Hajnovský., Přívazek zahrnuje pouze I. část celého svazku: Seznam rostlin jevnosnubných v nejbližším okolí mladoboleslavském samorostlých i obecněji pěstovaných, and Přívazek k : Biologické listy: 4-5 (1915-1916)
A portable open gas-exchange system (Li-6400, Li-Cor, Inc., Lincoln, NE, USA) has been widely used for the measurement of net gas exchanges and calibration/parameterization of leaf models. Measurement errors due to diffusive leakage rates of water vapor (LW) and CO2 (LC) between inside and outside of the leaf chamber, and the inward dark transpiration rate (DW) and dark respiration rate (DC) released from the leaf under the gasket, can be significant. Rigorous model-based approaches were developed for estimating leakage coefficients of water vapor (KW) and CO2 (KC) and correcting for the combination of these errors. Models were based on mass balance equations and the Dusty Gas Model for a ternary gas mixture of water vapor, CO2, and dry air. Experiments were conducted using two Li-6400 systems with potato and soybean leaves. Results indicated that models were reliable for estimating KW and KC, and the values varied with instrument, chamber size, gasket condition, and leaf structure. A thermally killed leaf should be used for this determination. Measurement error effects on parameterization of the Farquhar et al. (1980) model as determined by PN/C i curves were substantial and each parameter had its own sensitivity to measurement errors. Results also indicated that all four error sources should be accounted for when correcting measurements., Q. Wang ... [et al.]., and Obsahuje bibliografii a dodatky