4-year-old Pinus koraiensis, planted in open-top chambers at Changbai Mountain Station, received three different treatments [700 µmol(CO2) mol-1 = EC, control chamber = CC, and field = F]. Saturated net photosynthetic rate (PN) was 62 % higher in EC plants compared to CC and F plants as shown by PAR/PN response curves. Despite the increased PN, EC plants still showed decreased photosynthetic capacity when compared with CC and F plants at the same measurement CO2 concentration. EC plants had the highest stomatal conductance (gs) and ratio of intercellular to ambient CO2 concentration (Ci/Ca) compared with CC and F plants when measured at the same CO2 concentration. The Ci/Ca ratio was a sensitive indicator of stomatal behaviour, but not of photosynthesis. The responses of gs to EC did not correlate in magnitude or direction with responses of PN to EC. There was no significant difference in the number of stomata lines and stomata between EC and Ca. and Y. M. Zhou, S. J. Han.
72 to 120 h of soil flooding of barley plants (Hordeum vulgare L. cv. Alfa) led to a noticeable decrease in the rates of CO2 assimilation and transpiration, and in chlorophyll and dry mass contents. Stomatal conductance decreased following flooding without appreciable changes in the values of intercellular CO2 concentrations. A drop in the activity of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and of the photorespiratory enzymes phosphoglycollate phosphatase (EC 3.1.3.18) and glycollate oxidase (EC 1.1.3.1) was observed, while the activity of phosphoenolpyruvate carboxylase (EC 4.1.1.31) increased in all flooded plants. Flooding of barley plants caused an increase in proline content and in leaf acidity. and R. Y. Yordanova, L. P. Popova.
European beech (Fagus sylvatica L.) seedlings of three different origins were used to evaluate the effect of water deficit and recovery during the most vulnerable phase of forest tree life. Gas-exchange characteristics and fluorescence rapid light curves were studied in the seedlings from a warm region (PV1, 530 m a.s.l.), seedlings from a moderately warm region (PV2, 625 m a.s.l.), optimal for beech, and in seedlings from a cool region (PV3; 1,250 m a.s.l.). Changes in photosynthetic characteristics caused by water deficit were similar, but their intensity was dependent on the origin of the seedlings. Simulation of drought conditions by the interruption of watering led to a decrease in the efficiency of primary photochemistry in PSII, with the most significant decrease in the PV2 seedlings. Conversely, water deficit affected most significantly gas exchange in PV3, where the recovery process was also the worst. The PV1 demonstrated the highest resistance to water deficit. Drought-adaptation of beech seedlings at non-native sites seems to be linked to water availability and to the origin of the beech seedlings., E. Pšidová, Ľ. Ditmarová, G. Jamnická, D. Kurjak, J. Majerová, T. Czajkowski, A. Bolte., and Obsahuje bibliografii
Response to irradiance of leaf net photosynthetic rates (PN) of four carrot cultivars: Cascade, Caro Choice (CC), Oranza, and Red Core Chantenay (RCC) were examined in a controlled environment. Gas exchange measurements were conducted at photosynthetic active radiation (PAR) from 100 to 1 000 μmol m-2 s-1 at 20 °C and 350 μmol (CO2) mol-1(air). The values of PN were fitted to a rectangular hyperbolic nonlinear regression model. PN for all cultivars increased similarly with increasing PAR but Cascade and Oranza generally had higher PN than CC. None of the cultivars reached saturation at 1 000 μmol m-2 s-1. The predicted PN at saturation
(PNmax) for Cascade, CC, Oranza, and RCC were 19.78, 16.40, 19.79, and 18.11 μmol (CO2) m-2 s-1, respectively. The compensation irradiance (I c) occurred at 54 μmol m-2 s-1 for Cascade, 36 μmol m-2 s-1 for CC, 45 μmol m-2 s-1 for Oranza, and 25 μmol m-2 s-1 for RCC. The quantum yield among the cultivars ranged between 0.057-0.033 mol(CO2) mol-1(PAR) and did not differ. Dark respiration varied from 2.66 μmol m-2 s-1 for Cascade to 0.85 μmol m-2 s-1 for RCC. As PN increased with PAR, intercellular CO2 decreased in a non-linear manner. Increasing PAR increased stomatal conductance and transpiration rate to a peak between 600 and 800 μmol m-2 s-1 followed by a steep decline resulting in sharp increases in water use efficiency. and S. Kyei-Boahen ... [et al.].
Small rainfall events (≤ 5 mm) have short intervals, but account for a large proportion of the annual rainfall frequency in arid lands. To explore possible strategies used by desert plants to utilize the small rainfall events, we investigated the photosynthetic responses of 28 species to 1 mm and 6 mm of simulated rainfall in the Junggar Basin, northwest China. The species were grouped into four plant functional types: short-life-cycle herbs, long-life-cycle herbs, non-phreatophyte shrubs, and phreatophyte shrubs. The results showed that the net photosynthetic rate, stomatal conductance, and transpiration rate increased in most of the herbs, but they responded differently to the rainfall treatments. However, the water-use efficiency did not significantly differ after 1 and 6 mm rainfall treatments in most of the shrubs. The maximum water absorption by leaves and the percentage increase of a leaf water content (LWC) were higher in the herbs than those in the shrubs. Plants with dense trichomes had the highest LWC. The results suggested that the desert plants benefited from the
micro-environment humidity provided by the small rainfall events., Y. Wu, X. J. Zheng , Y. Li., and Obsahuje seznam literatury
The thermo-sensitivity of two new pea (Pisum sativum L.) cultivars-Afila (mutant in the gene transforming leaves into mustaches) and Ranen (mutant for early ripening)-as compared to the control cultivar Pleven-4 to either low (4 °C, T4) or high temperature (38 °C, T38) was investigated by means of chlorophyll (Chl) fluorescence kinetics. The low temperature treatment decreased the photosynthetic activity, measured via a decline of the Chl fluorescence decrease ratios RFd690 and RFd735, and this was mainly due to a decline of the Chl fluorescence decrease parameter Fd and maximum Chl fluorescence Fm. In the new cv. Ranen the RFd ratios at first decreased and increased again after 24-h exposure to 4 °C, indicating its good acclimation ability to low temperature. The cold-induced changes in the photosynthetic performance of all cultivars were reversed after transferring plants back to 23 °C for 48 h. In the Chl and carotenoid (Car) contents no or little changes occurred during the T4 treatment, except for a slight but clear increase of the ratio Chl a/b and a decrease in the ratio Chl/Car. In contrast to this, the T38 treatment for 72 h decreased the RFd ratios more strongly than the T4 exposure did. In fact, an irreversible injury of the photosynthetic apparatus was caused in the control pea cv. Pleven-4 by a 48-h T38 exposure and for the new cv. Afila after a 72-h T38 exposure. In contrast, the cv. Ranen was less and little sensitive to the T38 exposure. In the heat-sensitive cvs. Pleven-4 and Afila, the decrease in RFd values at T38 was associated with a strong decline of the Chl a+b and total Car contents. The Chl a+b decline could also be followed via an increase of the Chl fluorescence ratio F690/F735. Parallel to this, a strong decline of Chl a/b from ca. 3.0 (range 2.85-3.15) to ca. 1.9 (range 1.85-1.95) occurred indicating a preferential decline of the Chl a-pigment proteins but not of the Chl a/b-pigment protein LHC2. In the relatively heat-tolerant cv. Ranen, however, the ratio Chl a/b declined only partially. After the T4 treatment the stress adaptation index Ap was higher in cv. Ranen than in controls and reached in heat-treated Ranen plants almost the starting value indicating a cold and heat stress hardening of the treated plants. The Chl fluorescence parameters and pigment contents were influenced by T38 and T4 treatments in various ways indicating that the mechanisms of low and high temperature injury of the photosynthetic apparatus are different. The new cv. Ranen exhibited a cross tolerance showing a fairly good acclimation ability to both T4 and T38, hence it is a very suitable plant for outdoor growth and for clarification of the accl, imation mechanisms to unfavourable temperatures., and K. Georgieva, H. K. Lichtenthaler.
Ferns flourish in many habitats, from epiphytic to terrestrial and from sunny to shady, and such varied conditions require contrasting photosynthetic strategies to cope with drought. Four species of temperate ferns from different habitats were subjected to drought by withholding irrigation in order to investigate their photosynthetic responses. Lepisorus thunbergianus (epiphytic) had low stomatal density and showed high water-use efficiency (WUE) retaining photosynthetic activity with low relative frond water content under drought stress, which suggested their high adaptation to drought. On the other hand, low WUE with low light-saturated photosynthetic rate in Adiantum pedatum (terrestrial, shady environment) was associated with much lower photosynthesis than in the other species under drought stress, suggesting lower adaptation to drought-prone habitats. Morphological stomatal traits such as stomatal density and photosynthetic response to drought in ferns involved species-specific adaptation to survive and grow in their natural habitats with different levels of drought., K. Nishida, Y. T. Hanba., and Obsahuje seznam literatury
Alterations in photosynthetic performance of lutein-deficient mutant lut2 and wild type (wt) of Arabidopsis thaliana were followed after treatment with low temperature and high light for 6 d. The obtained results indicated lower electrolyte leakage, lower excitation pressure, and higher actual photochemical efficiency of PSII in lut2 plants exposed to combined stress compared to wt plants. This implies that lut2 is less susceptible to the applied stress conditions. The observed lower values of quantum efficiency of nonphotochemical quenching and energy-dependent component of nonphotochemical quenching in lut2 suggest that nonphotochemical quenching mechanism(s) localized within LHCII could not be involved in the acquisition of higher stress tolerance of lut2 and alternatives to nonphotochemical quenching mechanisms are involved for dissipation of excess absorbed light. We suggest that the observed enhanced capacity for cyclic electron flow and the higher oxidation state of P700 (P700+), which suggests PSI-dependent energy quenching in lut2 plants may serve as efficient photoprotective mechanisms, thus explaining the lower susceptibility of lut2 to the combined stress treatments.
Plants of Podophyllum hexandrum, collected from lower, mid, and upper distribution limits in alpine Himalaya were studied under greenhouse conditions to evaluate the photosynthetic response. Net photosynthetic rates (PN), stomatal conductance (gs), and efficiency of carbon uptake increased with altitude. The maximum PN and gs were measured in the considered population during the 3-6th week of development. PN and gs decreased on an average by 58 and 48 % from maximum rates reached around 4th week to the 10th week of growth, respectively. The photosynthetic response in the three ecotypes appeared to be genetically controlled. and S. K. Vats, S. Kumar.
The poikilochorophyllous, desiccation-tolerant (PDT) angiosperm, Pleurostima purpurea, normally occurs in less exposed rock faces and slightly shady sites. Our aim was to evaluate the light susceptibility of the photosynthetic apparatus during dehydration-rehydration cycle in P. purpurea. In a controlled environment, the potted plants were subjected to water deficit under two different photosynthetic photon flux densities [PPFD, 100 and 400 μmol(photon) m-2 s-1]. In the higher PPFD, net photosynthetic rate (PN) become undetectable after stomata closure but photochemical efficiency of photosystem II, electron transport rate, and photochemical quenching coefficient were maintained relatively high, despite a partial decrease. The photochemical activity was inhibited only after the complete loss of chlorophylls, when leaf relative water content dropped below 72% and total carotenoids reached maximal accumulation. Nonphotochemical energy dissipation increased earlier in response to dehydration under higher PPFD. PN and photochemical activity were fully recovered after rehydration under both light treatments. Our results suggested that the natural occurrence of P. purpurea should not be restricted by the light intensity during the complete desiccation-rehydration cycles., S. T. Aidar, S.T. Meirelles, R. F. Oliveira, A. R. M. Chaves, P. I. Fernandes-Júnior., and Obsahuje bibliografii