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
The effects of shade on the growth, leaf photosynthetic characteristics, and chlorophyll (Chl) fluorescence parameters of Lycoris radiata var. radiata were determined under differing irradiances (15, 65, and 100% of full irradiance) within pots. The HI plants exhibited a typical decline in net photosynthetic rate (PN) during midday, which was not observed in MI- and LI plants. This indicated a possible photoinhibition in HI plants as the ratio of variable to maximum fluorescence (Fv/Fm) value was higher and the minimal fluorescence (F0) was lower in the, and LI plants. Diurnal patterns of stomatal conductance (gs) and transpiration rate (E) were remarkably similar to those of PN at each shade treatments, and the intercellular CO2 concentration (Ci) had the opposite change trend. Under both shading conditions, the light saturation point, light compensation point and photon-saturated photosynthetic rate (Pmax) became lower than those under full sunlight, and it was the opposite for the apparent quantum yield (AQY). The higher the level of shade, the lower the integrated daytime carbon gain, stomatal and epidermis cell densities, specific leaf mass (SLM), bulb mass ratio (BMR), leaf thickness, and Chl a/b ratio. In contrast, contents of Chls per dry mass (DM), leaf area ratio (LAR), leaf mass ratio (LMR), leaf length, leaf area and total leaf area per plant increased under the same shade levels to promote photon absorption and to compensate for the lower radiant energy. Therefore, when the integrated daytime carbon gain, leaf area and total leaf area per plant, which are the main factors determining the productivity of L. radiata var. radiata plant, were taken into account together, this species may be cultivated at about 60-70% of ambient irradiance to promote its growth. and S. B. Zhou ... [[et al.].
The photosynthetic performances of regenerated protoplasts of Bryopsis hypnoides, which were incubated in seawater for 1, 6, 12, and 24 h, were studied using chlorophyll (Chl) fluorescence and oxygen measurements. Results showed that for the regenerated protoplasts, the pigment content, the ratios of photosynthetic rate to respiration rate, the maximal photosystem II (PSII) quantum yield (Fv/Fm), and the effective PSII quantum yield (ΦPSII) decreased gradually along with the regeneration progress, indicated that during 24 h of regeneration there was a remarkable reduction in PSII activity of those newly formed protoplasts. We assumed that during the cultivation progress the regenerated protoplasts had different photosynthetic vigor, with only some of them able to germinate and develop into mature thalli. The above results only reflected the photosynthetic features of the regenerated protoplasts at each time point as a whole, rather than the actual photosynthetic activity of individual aggregations. Further investigation suggested a relationship between the size of regenerated protoplasts and their viability. The results showed that the middle-sized group (diameter 20-60 μm) retained the largest number of protoplasts for 24 h of growth. The changes in Fv/Fm and ΦPSII of the four groups of differently sized protoplasts (i.e. < 20, 20-60, 60-100, and > 100 μm) revealed that the protoplasts 20-60 μm in diameter had the highest potential activity of the photosynthetic light energy absorption and conversion for several hours. and F. Lü, G. C. Wang, J. F. Niu.
In search for new forestation tree species for future Central European climate conditions, Mediterranean evergreen oak taxa are investigated for their summer drought- and winter frost-hardiness. Here we report on the winter performance of the photosynthetic apparatus of Quercus × hispanica Lam. and its evergreen parental species Q. suber L. under extraordinary harsh winter conditions. Both taxa showed a strong decline of photosystem II (PSII) quantum efficiency (Fv/Fm) with a concomitant increase in the deepoxidation state (DES) of the xanthophyll pigments depending on (severe) frost events during winter, and these parameters significantly correlated with minimum air temperatures during periods of chronic photoinhibition at mid-winter, but not at the onset of winter in response to the first frost nights. Fv/Fm and DES correlated with each other in both taxa throughout the winter. and V. Holland, W. Brüggemann.
Picea glehnii Masters can grow in strongly acidic volcanic ash soil (pH 3.6) in northern Japan. We compared needle longevity, photosynthetic rate, and concentrations of elements in needles, in mature trees of P. glehnii growing in volcanic ash soil and in brown forest soil (pH 5.4). P. glehnii growing in volcanic ash soil showed suppressed photosynthetic rate and growth by the deficiency in nitrogen compared with its growth in brown forest soil. However, the younger needles of P. glehnii growing in volcanic ash soil maintained a high photosynthetic rate, as a result of large amounts of remobilized nitrogen from senesced needles. Needles of P. glehnii growing in volcanic ash soil did not show deficiencies in Ca, Mg, or K. Moreover, Al was at low levels in the needles, suggesting that P. glehnii was able to avoid Al toxicity by Al exclusion. P. glehnii thus exhibits great ability to adapt to an acidic environment. and M. Kayama, F. Satoh, T. Koike.
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
Pasture soils in the Amazon become unsustainable after a short period of use, typically being replaced by emergent secondary vegetation (capoeira). The aim of this research was to investigate the photosynthetic capacity and water use in the most common tree species (Vismia japurensis, Vismia cayennensis, Bellucia grossularioides, Laetia procera, and Goupia glabra) in successional chronosequence. This study was carried out in secondary vegetation area with ages that vary between 1 and 19 years. Responses of gas exchange were determined during different periods of precipitation. The gas exchange decreased with advancing age of the vegetation (1-19 years), except for G. glabra. Negative relationships of PNmax as a function of aging observed for V. japurensis, V. cayennensis, B. grossularioides, and L. procera exhibited r2 equal to 0.59, 0.42, 0.33, and 0.58, respectively. The species of Vismia showed higher values for photosynthetic parameters in relation to other species across the chronosequence. Overall, there were differences in gas exchange only for some species between the different periods of precipitation. Therefore, our results suggest a distinct pattern of photosynthetic responses to species in early succession. Light decrease can exert a decisive role to reduce the photosynthetic rates in secondary succession species. On the other hand, the results of WUE showed weak evidence of changes for the species during dry and rainy periods in the abandoned pasture in central Amazonia. and C. E. M. Silva, J. F. C. Goncalves, E. G. Alves.
Gas exchange of Carex cinerascens was carried out in Swan Islet Wetland Reserve (29°48' N, 112°33' E). The diurnal photosynthetic course of C. cinerascens in the flooded and the nonflooded conditions were analyzed through the radial basis function (RBF) neural network approach to evaluate the influences of environmental variables on the photosynthetic activity. The inhibition of photosynthesis induced by soil flooding can be attributed to the reduced stomatal conductance (gs), the deficiency of Rubisco regeneration and decreased chlorophyll (Chl) content. As revealed by analysis of artificial neural network (ANN) models, gs was the dominant factor in determining the photosynthesis response. Weighting analysis showed that the effect of water pressure deficit (VPD) > air temperature (T) > CO2 concentration (Ca) > air humidity (RH) > photosynthetical photon flux density (PPFD) for the nonflooded model, whereas for the flooded model, the factors were ranked in the order VPD > C a > RH > PPFD > T. The different photosynthetic response of C. cinerascens found between the nonflooded and flooded conditions would be useful to evaluate the flood tolerance at plant species level. and M. Li ... [et al,.].