The effect of Potato virus Y NTN (PVY) infection upon photosynthesis was analysed in transgenic Pssu-ipt tobacco overproducing endogenous cytokinins in comparison with control, nontransgenic Nicotiana tabacum plants. The course of the infection from the early to the late stage was monitored by measuring of photosynthetic gas exchange and fast chlorophyll (Chl) a fluorescence induction kinetics. Leaf photosynthesis was also analysed using Chl fluorescence imaging (Chl-FI). From the different fluorescence parameters obtained using Chl-FI, the nonphotochemical quenching (NPQ) proved to be the most useful parameter to assess the effect of PVY infection. On the other hand, Chl-FI was found to be inapplicable for any presymptomatic detection of PVY infection in tobacco. The lower accumulation of the virus was found in transgenic plants and corresponded also with the presence of visible symptoms of PVY infection. The net photosynthetic rate (PN), transpiration rate (E), and stomatal conductance (gs) significantly decreased with the progress of the infection in both control plant types and transgenic rooted plants, while transgenic grafts were much less affected. The analysis of the Chl fluorescence transient revealed higher number of silent dissipative reaction centres, higher nonphotochemical dissipation, and significantly lower performance index, PI(abs), in the healthy transgenic grafts. Chl-FI also confirmed significantly higher NPQ in transgenic grafts., P. Spoustová ... [et al.]., and Obsahuje bibliografii
In order to assess the long-term impacts of saline groundwater irrigation to Haloxylon ammodendron, one of the main shrubs in the Tarim desert highway ecological shelterbelt, we irrigated the H. ammodendron seedlings with progressive saline groundwater (3-30 g L-1, simulation environment in the Tarim desert highway ecological shelterbelt) and investigated the diurnal variations of chlorophyll a (Chl a) fluorescence parameters, such as maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm), quantum yield of photochemical energy conversion in PSII (YII), the apparent rate of electron transport at the PSII level (ETR), photochemical quenching coefficient (qP), non-photochemical quenching (NPQ), quantum yield of nonregulated non-photochemical energy loss in PSII (YNO) and quantum yield of regulated non-photochemical energy loss in PSII (YII), at approximately 2-h intervals. Fv/Fm with 5 g L-1 (S2) was lower than that with 2 g L-1 (S1) but a little higher than 20 g L-1 (S5), respectively. Under the low light [photosyntheticallyactive radiation (PAR) ≤ 250 μmol m-2 s-1, at 08:00, 10:00 and 20:00 h of the local time], S1 kept the lowest YII and the highest YNPQ; while under the high light (PAR ≥ 1500 μmol m-2 s-1), the YII performed S1>S2>S5, and the reverse YNPQ; under mild light (250 μmol mt-2 s-1 ≤ PAR ≤ 1500 μmol m-2 s-1), S1 remained the highest YII, no matter the light and the salinity, the similar YNO almost occurred basically. The results showed that the sand-binding plant H. ammodendron could regulate its energy-utilizing strategies. The S2 might be the most suitable salinity of the irrigation water for H. ammodendron in the Tarim desert highway ecological shelterbelt in the northwest of China. and W. Han ... [et al.].
Chlorophyll (Chl) a fluorescence parameters and rapid light curves of soybean [Glycine max (L.) Merrill] were measured by pulse amplitude modulation fluorometry. Measurements were taken during different stages of soybean growth under field conditions with 20% enhancement in ultraviolet-B (UV-B) radiation. Results showed that supplemental UV-B radiation decreased Chl contents by 5.5% (P=0.048), 8.7% (P=0.046), and 10.5% (P=0.005) in seedling, in branching-flowering, and in pod-setting stages, respectively. In the branching-flowering and pod-setting stages, maximum quantum yield of photosystem (PS) II photochemistry (Fv/Fm) decreased by 6.1% (P=0.001) and 3.0% (P=0.009), respectively. Supplemental UV-B radiation significantly decreased the effective quantum yield (Y). The photosynthetic capacity at light saturation (Pm) also decreased in both the seedling and branching-flowering stages by 28.9% (P=0.007) and 15.5% (P=0.041), respectively. However, Y and Pm showed no significant difference in the trefoil and pod-setting stages with and without the UV treatment. The light saturation parameter (E k) decreased by 21.1% (P=0.000) and 23.2% (P=0.029) in the trefoil and seedling stages, respectively. Moreover, the initial slope (α) decreased by 21.1% (P=0.001) in the branching-flowering stage. Nonphotochemical quenching (NPQ) in the seedling stage and photochemical quenching coefficient (qp) in the
branching-flowering stage decreased significantly under UV-B treatments. The results of the present study suggest that supplemental UV-B radiation adversely affected Chl content and electron transport activity in PSII and consequently decreased the photosynthetic efficiency of soybean plants., Z. Hu ... [et al.]., and Obsahuje bibliografii
This study examined the utility of the ratio of variable fluorescence to maximum fluorescence (Fv/Fm) to detect freezing injury on buds of two Vitis vinifera cultivars: Pinot noir and Pinot gris. Freezing treatments on buds caused a decrease both in Fv/Fm and percentage of budburst, more severely on Pinot gris than Pinot noir, specifically at the lower temperature (-20°C). Fv/Fm ratio showed a close correlation with percentage of budburst, and a threshold of the lethal Fv/Fm was proposed as an indicator of bud mortality. and L. Zulini, C. Fischer, M. Bertamini.
a1_Photosynthesis is one of the most important processes in plant biology and in the development of new methodologies that allow a better understanding and characterization of the photosynthetic status of organisms, which is invaluable. Flow cytometry (FCM) is an excellent tool for measuring fluorescence and physical proprieties of particles but it has seldom been used in photosynthetic studies and thus the full extent of its potentialities, in this field of research, remains unknown. To determine the suitability of FCM in photosynthesis studies, pea plants were exposed to Paraquat and their status was analyzed during 24 h. FCM was used to evaluate the integrity (volume and internal complexity) and the relative fluorescence intensity (FL) of chloroplasts extracted from those plants. To elucidate which type of information the FL conveys, FL values were correlated with the minimum fluorescence level (F0), maximum fluorescence level (Fm) and maximum photochemical efficiency of PSII (Fv/Fm), obtained by using Pulse-Amplitude-Modulation (PAM) fluorometry. Results indicate that: (1) the biomarkers used to evaluate the structural integrity of the chloroplasts were more sensitive to Paraquat exposure than the ones related to fluorescence; (2) the variation of the chloroplast’s structure, as time progressed, pointed to a swelling and subsequent burst of the chloroplast which, in turn, compromised fluorescence emission; (3) FL presented a high and significant correlation with the Fv/Fm and to a lesser degree with Fm but not with F0; (4) pigment content did not reveal significant changes in response to Paraquat exposure and is in agreement with the proposed model, suggesting that the cause for fluorescence decrease is due to chloroplast disruption., a2_In sum, FCM proved to be an outstanding technique to evaluate chloroplastidal functional and structural status and therefore it should be regarded as a valuable asset in the field of photosynthetic research., E. Rodriguez ... [et al.]., and Obsahuje bibliografii
Changes in chloroplastidic pigments, gas exchange and carbohydrate concentrations were assessed during the rapid initial expansion of C. guianensis leaflet. Leaves at metaphyll stage were tagged and assessments were carried out 14, 17, 20, 23, 27, and 31 days later. Pigments synthesis, distribution and accumulation were uniform among leaflet sections (basal, median and apical). Chlorophyll (Chl) a, Chl b, Chl (a+b), and total carotenoids (Car) concentrations were significantly increased after 27 days from metaphyll, and the most expressive increases were parallel to lower specific leaflet area. Chl a/b was lower on day 14 and it was increased on subsequent days. Negative net photosynthesis rate (PN), and the lowest stomatal conductance (gs) and transpiration (E) were registered on day 14, following significant increases on subsequent days. The Chl (a+b) and Chl a effects on PN were more expressive until day 20. Intercellular to ambient CO2 concentration ratio (Ci/Ca) was higher on day 14 and lower on subsequent days, and no stomatal limitation to CO2 influx inside leaflets was observed. Leaflet temperature was almost constant (ca. 35°C) during leaflet development. Sucrose and starch concentrations were increased in parallel to increases in PN. Altogether, these results highlight the main physiological changes during C. guianensis leaflet expansion and they should be considered in future experiments focusing on factors affecting PN in this species. and F. K. C. Moraes ... [et al.].
Článek přestavuje taxonomicky problematický rod chrpa z čeledi Asteraceae. Jsou diskutovány současné pohledy na vymezení a vnitřní členění rodu založené na molekulárních znacích. Dále je popsána problematika hybridizace, která je v rodu velmi častá, a její souvislost s polyploidií (druhy stejné ploidie se často kříží za vzniku rozsáhlých a variabilních hybridních rojů, zatímco mezi ploidiemi je silná reprodukční bariéra)., Centaurea is a taxonomically critical genus from the Asteraceae family. Current delimitation of the genus and its internal classification based on molecular data are discussed. Hybridization and polyploidy are common in Centaurea. The frequency of hybridization depends on ploidy levels of the taxa (homoploid taxa usually hybridize easily and form extensive and variable hybrid swarms, while heteroploid taxa are reproductively strongly isolated)., and Petr Koutecký.
Most organisms inhabiting earth feed directly or indirectly on the products synthesized by the reaction of photosynthesis, which at the current atmospheric CO2 levels operates only at two thirds of its peak efficiency. Restricting the photorespiratory loss of carbon and thereby improving the efficiency of photosynthesis is seen by many as a good option to enhance productivity of food crops. Research during last half a century has shown that several plant species developed CO2-concentrating mechanism (CCM) to restrict photorespiration under lower concentration of available CO2. CCMs are now known to be operative in several terrestrial and aquatic plants, ranging from most advanced higher plants to algae, cyanobacteria and diatoms. Plants with C4 pathway of photosynthesis (where four-carbon compound is the first product of photosynthesis) or crassulacean acid metabolism (CAM) may consistently operate CCM. Some plants however can undergo a shift in photosynthetic metabolism only with change in environmental variables. More recently, a shift in plant photosynthetic metabolism is reported at high altitude where improved efficiency of CO2 uptake is related to the recapture of photorespiratory loss of carbon. Of the divergent CO2 assimilation strategies operative in different oraganisms, the capacity to recapture photorespiratory CO2 could be an important approach to develop plants with efficient photosynthetic capacity. and S. K. Vats, S. Kumar, P. S. Ahuja
Geitlerinema amphibium (BA-13), mat-forming cyanobacterium from the southern Baltic Sea, was grown at three irradiances [5, 65, and 125 μmol(photon) m-2 s-1] and three temperatures (15, 22.5, and 30°C). To determine the effect of the investigated factors and their interaction on culture concentration, pigment content, and photosynthetic parameters of cyanobacterium, factorial experiments and two-way analysis of variance (ANOVA) were carried out. Both chlorophyll (Chl) a and phycobilins (PB) were influenced by the irradiance and temperature, but stronger effect was noted in the case of the former one. Chl a and PB concentration per 100 μm of filament dropped above 4-fold with the increasing irradiance. The ratios between individual carotenoids [β-carotene, zeaxanthin, and myxoxanthophyll (Myx)] and Chl a increased significantly with an increase in the irradiance. The greatest fluctuations were observed in the ratio of Myx to Chl a (above 10-fold). Thus, Myx was suggested as the main photoprotective carotenoid in G. amphibium. Based on photosynthetic light response (PI) curves, two mechanisms of photoacclimation in G. amphibium were recognized: a change of photosynthetic units (PSU) number and a change of PSU size. These two mechanisms constituted the base of significant changes in photosynthetic rate and its parameters, such as the compensation point (PC), the initial slope of photosynthetic curve (α), saturation irradiance (EK), maximal photosynthetic rate (Pmax), and dark respiration rate (RD). The greatest changes were observed in PC values (about 15-fold within the range of the factors tested). Studied parameters showed a wide range of changes, which might indicate G. amphibium ability to acclimatize well to irradiance and temperature, and indirectly might explain the successful growth of cyanobacterium in dynamically changing environmental conditions., S. Jodłowska, A. Latała., and Obsahuje bibliografii
The present piece of work highlights the comparative effects of two active forms of brassinosteroids (BRs), 28-homobrassinolide (HBL) and 24-epibrassinolide (EBL), on growth parameters, carbonic anhydrase activity and photosynthetic parameters in Lycopersicon esculentum (cv. K-21) sampled at 45 (24 h after spray) and 60 days after sowing, under natural conditions. Out of the two active forms of BR, EBL proved better than HBL in improving the above parameters, when applied as foliar spray. Of the three concentrations (10-6 M, 10-8 M or 10-10 M) of HBL and EBL, 10-8M proved best in both cases. and S. Hayat ... [et al.].