Irrespective of the originál habitat of cassava {Manihot esculenta Crantz) cultivars, net photosynthetic rate (P^) was substantially reduced in leaves developed in a cool climate as compared with warm-climate leaves. Cool-climate leaves paitially recovered their photosynthetic capacity after 7 d acclimation in warm climate. The hot-climate cultivar showed a broad optimum temperature from 30 to 40 "C, while the cool-climate cultivar showed an upward shift in optimum temperature in the acclimated and warm-climate leaves. In field-grown cassava, maximum of upper canopy leaves was greater than 40 pmol(C02) m'^ s'i when measured in high rainfall season and the rates did not show saturation by radiant energy up to 1800 pmol m'2 s'i PAR. The seasonal average of upper canopy leaves was significantly correlated with both root yield and harvestable biomass. The selection for high in parental materials may lead to high yields when combined with other yield determinants.
High abundance of cockspur (Echinochloa crus-galli) at the geothermal carbon dioxide spring area in Stavešinci indicates that this species is able to grow under widely varying CO2 concentrations. Living cockspur plants can even be found very close to gas-releasing vents where growth is significantly reduced. Plant height correlated well with CO2 exposure. The δ13C value of the CO2 spring air was -3.9 ‰ and δ13C values of high-, medium-, and low-CO2 plants were -10.14, -10.44, and -11.95 ‰, respectively. Stomatal response directly followed the prevailing CO2 concentrations, with the highest reduction of stomatal conductance in high CO2 concentration grown plants. Analysis of the curves relating net photosynthetic rate to intercellular CO2 concentration (PN-Ci curves) revealed higher CO2 compensation concentration in plants growing at higher CO2 concentration. This indicates adjustment of respiration and photosynthetic carbon assimilation according to the prevailing CO2 concentrations during germination and growth. There was no difference in other photosynthetic parameters measured. and D. Vodnik ... [et al.].
Four dones of Miscanthus spp., collected from regions with different rainfall distribution, were transplanted in pots and subjected to five drying cycles (each of 6- 7 d). Gas exchanges were measured on attached leaves, The light-saturated photosynthetic CO2 uptake (P^) began to dechne when the leaf water potential (y\) was reduced to -1.3 - -1.5 MPa, and the values corresponding to 50 % decrease P^)] were -1.6 - -2.6 MPa. The P^ ) values were lower in a cloně collected from Kilung (northem Taiwan, highly frequent rainfall) than in dones collected from Kenting (southem Taiwan, distinct wet and dry season). Besides, the ^(1/2 Pj^) value became lower in all the tested dones when the drying cycle advanced (in the drying cycle of northem Taiwan cloně and in the 5‘*’ drying cycle of southem Taiwan dones, řespectively). Both the stomatal and non- stomatal factors of photosynthesis were affected by water deficit, and the osmotic adjustment mitigated the negative impact of water deficit on both factors. The clonal differences in the tolerance and acdimation of photosynthesis to water deficit are dosely related to the osmotic adjustment, and the clonal differences in osmotic adjustment reflect the rainfall pattem of sampled region.
A differential response to long-term ozone exposures (50 and 100 mm3 m-3) was observed in the green and white areas of variegated leaves of Hedera canariensis var. azorica L. In green tissue the photosynthetic activity was depressed via a stomatal mechanism, and in white regions no effect was observed. Chlorophyll fluorescence parameters remained unchanged in green portions, whereas in the white ones Fm and Fv/Fm significantly diminished following ozone fumigation. and G. F. Soldatini ... [et al.].
Physiological responses from sensitive (S156) and resistant (R123) genotypes of ozone bioindicator, snap bean, were investigated after exposing the plants to cumulative, phytotoxic ozone amounts. Daily course of gas-exchange parameters showed delayed stomatal response in S156 leaves to environmental changes comparing to the response of R123 leaves. Potential photosynthetic quantum conversion, Stern-Volmer nonphotochemical quenching (NPQ), and maximum photochemical efficiency of PSII (Fv/Fm) values changed differently in the two genotypes between the first and last measuring days. We concluded that the higher ozone sensitivity originated at least partly from inferior regenerating and/or antioxidant capacity. Experimental protocol proved to be determinant on chlorophyll fluorescence parameters: Fv/Fm and NPQ declined at midday, and only the sensitive leaves showed a slight increase in NPQ between 12 h and 16 h. We explained these results by moderately high temperatures and shade-adapted state of our experimental plants under substantial ozone stress. On the base of temperature dependence of minimal fluorescence yield (F0), critical temperature proved to be higher than 32.7°C for Phaseolus vulgaris under these conditions. We found a strong linear correlation between NPQ and nonphotochemical quenching of F0, indicating that NPQ was determined mostly by energy-dependent quenching (qE). The qE is the light-harvesting complex located component of NPQ and depends on the amount of zeaxanthin molecules bound in PSII proteins. Thus, difference between daily courses of NPQ in the two genotypes was probably due to different ways of utilization of the zeaxanthin pool under the interactive effect of ozone and moderate heat stress., V. Villányi, Z. Ürmös, B. Turk, F. Batič, Z. Csintalan., and Obsahuje bibliografii
The photosynthetic characterization of Populus euphratica and their response to increasing groundwater depth and temperature were analyzed based on net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci), transpiration rate (E), water use efficiency (WUE) and stomatal limitation (Ls) measured by a portable gas-exchange system (LI-6400) in the lower reaches of the Tarim River. Light-response curves were constructed to obtain light-compensation and light-saturation points (LCP and LSP), maximum photosynthetic rates (Pmax), quantum yields (AQY), and dark respiration rates (RD). The growth condition of P. euphratica, soil moisture, and groundwater depth in the plots were analyzed by field investigation. The results showed that the growth condition and photosynthetic characterization of P. euphratica were closely related to groundwater depth. The rational groundwater depth for the normal growth and photosynthesis was 3-5 m, the stress groundwater depth for mild drought was more than 5 m, for moderate drought was more than 6 m, for severe drought was more than 7 m. However, P. euphratica could keep normal growth through a strong drought resistance depended on the stomatal limitation and osmotic adjustment when it faced mild or moderate drought stress, respectively, at a normal temperature (25°C). High temperature (40°C) significantly reduced PN and drought stress exacerbated the damage of high temperature to the photosynthesis. Moreover, P. euphratica would prioritize the resistance of high temperature when it encountered the interaction between heat shock and water deficit through the stomata open unequally to improve the transpiration of leaves to dissipate overheating at the cost of low WUE, and then resist water stress through the osmotic adjustment or the stomatal limitation. and H. H. Zhou ... [et al.].
While photosynthesis of soybean has been enhanced by breeding, it remains to be clarified whether the improvement of root function could bring a further increase of photosynthetic capacity for the development of soybean cultivars. The objective of this grafting experiment was to determine the influence of record-yield soybean cultivars, Liaodou14 (L14) and Zhonghuang35 (Z35), as rootstocks on photosynthetic traits of cultivars released in different decades. Grafting of various soybean cultivars onto L14 or Z35 rootstocks showed a higher root physiological activity, which resulted in significant increases in some photosynthetic traits at the late grain-filling stage compared with the non-grafted and self-grafted plants. The genetic gain for some photosynthetic traits of cultivars released from 1966 to 2006 increased by using L14 and Z35 as rootstocks. It suggested that the photosynthetic traits of the recently released cultivars could increase more if their root functions are improved., S. Y. Li, F. Teng, D. M. Rao, H. J. Zhang, H. Y. Wang, X. D. Yao, C. M. Yu, C. H. Li, M. Z. Zhao, S. K. St. Martin, F. T. Xie., and Obsahuje seznam literatury
Predicting the effects of increased ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion on temperate desert ecosystems requires better knowledge of the ecophysiological response of common moss species. The aim of the current work was to determine whether elevated UV-B radiation affected photosynthetic performance and chloroplast ultrastructure of two moss crusts and whether response differences were observed between the crusts. In laboratory experiments, Bryum argenteum and Didymodon vinealis, which show microdistributions and are dominant in soil crusts at the Tengger Desert, Northern China, were subjected to four levels of UV-B radiation of 2.75 (control), 3.08, 3.25, and 3.41 W m-2 for 10 days, simulating 0, 6, 9, and 12% of stratospheric ozone at the latitude of Shapotou, respectively. The results showed that chlorophyll a fluorescence parameters (i.e., the maximal quantum yield of PSII photochemistry, the effective quantum yield of PSII photochemistry, and photochemical quenching coefficient), pigment contents, soluble protein contents, and the ultrastructure were negatively influenced by elevated UV-B radiation and the degree of detrimental effects significantly increased with the intensity of UV-B radiation. Moreover, results indicated that B. argenteum was probably more sensitive to supplementary UV-B radiation than D. vinealis. Therefore, we propose the use of B. argenteum crusts as a bioindicator of responses to elevated UV-B radiation., R. Hui, X. R. Li, R. L. Jia, L. C. Liu, R. M. Zhao, X. Zhao, Y. P. Wei., and Obsahuje bibliografii
In a growth chamber experiment, we determined net photosynthetic rate (PN) and leaf developmental characteristics of cultivars of a relatively small-, intermediate-, and a large-leaf genotype grown under irradiance of 450-500 µmol(photon) m-2 s-1 (HI), shade [140-160 µmol(photon) m-2 s-1] (LI), and after a shade-to-irradiation (LI >>HI) transfer. Differences in physiological responses of the genotypes were more pronounced in HI and LI>>HI plants than in LI plants. The small- and intermediate-leaf sizes had greater PN in the first measured leaf than the large-leaf type by 70 and 63 % in HI plants, and by 23 and 18 % in LI>>HI plants, respectively. Similar relationships were observed in the next developed leaf. The LI plants did not differ significantly in PN. Greater PN in the small- and intermediate-leaf size genotypes were not associated with greater total dry matter of the plant. Under irradiation, the large-leaf genotype accumulated more total nonstructural saccharides (TNS) and starch than the small- or intermediate-leaf size plants. TNS and starch concentrations in LI plants were about one-half those of HI and LI>>HI plants. These results should help to develop management practices that capitalize upon the competitive features of white clover in mixed-species swards. and D. P. Malinowski, D. P. Belesky, J. Fedders.
The effects of water deficit on photochemical parameters and activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were investigated in two olive cultivars differing in drought tolerance - 'Chemlali' and 'Chetoui'. After 30 days without irrigation, leaf water potential fell to -5.5 MPa that was accompanied by a marked decrease in net photosynthesis in 'Chetoui' olive cultivar. Maximal efficiency of PSII photochemistry (Fv/Fm) decreased slightly in 'Chemlali' (28 %) and substantially in 'Chétoui' (47 %). Both cultivars showed a similar decline (about 25 %) in the photochemical quenching coefficient, but only the drought-sensitive olive cultivar exhibited an enhancement (31 %) of non-photochemical fluorescence quenching under water deficit conditions. The quantum yield of electron transport decreased in both olive cultivars. 'Chemlali' showed a higher protection against oxidative stress, as judged from the lower levels of the malondialdehyde production. Catalase activity was higher in 'Chetoui'. Glutathione reductase activity was increased similarly in both olive cultivars under water stress. Ascorbate peroxidase activity was enhanced in 'Chemlali' under water stress, but was unaffected in 'Chetoui'. While, superoxide dismutase activity was inhibited in both cultivars under water stress, but higher activity was detected in 'Chemlali'. Thus, the ability to increase ascorbate peroxidase and a higher superoxide dismutase activity might be an important attribute linked to the drought tolerance in 'Chemlali' olive cultivar. and M. Guerfel ... [et al.].