In this work, photosystem II (PSII) photochemistry, leaf water potential, and pigment contents of male and female Pistacia lentiscus L. were investigated during a seasonal cycle at three different, arid locations: superior semiarid, inferior semiarid, and arid. The results showed that the gender, season, and the site conditions interacted to influence the quantum yield and pigment contents in P. lentiscus. Predawn leaf water status was determined only by the site and season. The annual patterns of PSII maximum quantum efficiency (Fv/Fm) were characterized by a suboptimal activity during the winter, especially, populations with the more negative water potential exhibited a lower chlorophyll (Chl) a content and chronic photoinhibition irrespective of a gender. We also demonstrated that both photochemical or nonphotochemical mechanisms were involved to avoid the photoinhibition and both of them depended on the season. This plasticity of photosynthetic machinery was accompanied by changes in carotenoids and Chl balance. In the spring, the female Fv/Fm ratio was significantly higher than in male individuals, when the sexual dimorphism occurred during the fruiting stage, regardless of site conditions. P. lentiscus sex-ratio in Mediterranean areas, where precipitations exceeded 500 mm, was potentially female-biased. Among the fluorescence parameters investigated, nonphotochemical quenching coefficient appeared as the most useful one and a correlation was found between Chl a content and Fv/Fm. These results suggest that functional ecology studies would be possible on a large scale through light reflectance analysis. and S. Ait Said ... [et al.].
The genetic basis of stomatal conductance (gs), net photosynthetic rate (PN), and transpiration rate (E) was explored by using a wheat doubled haploid population from a cross of Hanxuan10 and Lumai 14. The above three traits were evaluated in wheat flag leaves at 10, 20, 30 days after anthesis under drought stress (DS) and well-watered (WW), and quantitative trait loci (QTL) were analyzed. Expression of the traits during the grain filling stage showed downward trends under both conditions, but expression of three phenotypes were stronger under WW than those under DS. Extremely significant positive correlations were established among the traits at all growth stages under both conditions. A total of 18 additive QTLs for those traits were identified on 10 chromosomes. Among them, two batches of nine additive QTLs were associated with the target traits under DS and WW, respectively. Two additive QTLs for gs and E, two for gs and PN, six for gs, PN, and E clustered at the same or near the region (colocation) of chromosomes 4A, 2B, and 7B, respectively. This provided genetic basis for close phenotype correlations among gs, PN, and E. Furthermore, QTLs for gs, PN, and E near Xgwm577 and Xgwm611 located on 7B chromosome were linked to previously reported QTLs regulating a SPAD value and the chlorophyll a/b ratio under dark-induced condition. This finding indicated that these QTLs on 7B chromosome might be involved in the process of wheat leaf senescence., S. G. Wang, S. S. Jia, D. Z. Sun, H. Y. Wang, F. F. Dong, H. X. Ma, R. L. Jing, G. Ma., and Obsahuje bibliografii
Metabolite changes and senescence behaviour after mechanical phloem girdling were studied in leaf tissue of Quercus pubescens. Sugar accumulation is not only considered to be an important part of several developmental signalling pathways, but is also seen as one of the basic triggers for senescence induction, or at least an obligatory accessory phenomenon. Our survey showed that an accumulation of the soluble sugars, glucose and fructose, was not on its own obligatorily connected with the induction of leaf senescence, since no indication or even an onset of senescence could be observed during the course of the experiment. Instead, we observed an inhibition of leaf development with a decrease of photosynthesis and a slow-down of development in nearly all chlorophyll a fluorescence analysis parameters using the JIP-test. We detected a change of metabolites linked to oxidative stress, possibly due to an overexcitation of the developmentally inhibited photosynthetic apparatus., V. Holland, L. Fragner, T. Jungcurt, W. Weckwerth, W. Brüggemann., and Obsahuje bibliografii
Senescence constitutes the final stage of a plant organ and tissue development and is a subject to gene control and strict regulation. By the late growing season, when Alhagi sparsifolia entered the natural senescence period, a girdling treatment was carried out on the phloem to increase the sugar content in leaves and to investigate carbohydrate-induced leaf senescence. After the semi-girdling and full-girdling treatment, organic matter could not leave leaves due to the destruction of sieve tubes. This led to constantly increasing sugar contents in leaves. Girdling was shown to greatly accelerate the senescence of plants. In girdled leaves, chlorophyll (Chl) a, Chl b, carotenoids (Car), and both ratios of Chl a/b and Chl/Car were significantly reduced. On the donor side of PSII, the oxygen-evolving complex was inhibited under high concentrations of carbohydrates, which was manifested as the emergence of the K phase in fluorescence kinetic curves. On the acceptor side of PSII, the high carbohydrate content also led to the disruption of electron transport and reduced light-use efficiency, which was manifested as a reduction in numerous fluorescence parameters. We believe that the emergence and development of plant senescence was not necessarily induced by the high content of carbohydrates, because even a decrease in the carbohydrate concentration could not stop the senescence process. Although the high content of carbohydrates in plants could induce plant senescence, this kind of senescence was likely a pathological process, including degradations of physiological functions., G.-L. Tang, X.-Y. Li, L.-S. Lin, F.-J. Zeng, Z.-Y. Gu., and Obsahuje seznam literatury
Earth’s climate has experienced notable changes during the past 50-70 years when global surface temperature has risen by 0.8°C during the 20th century. This was a consequence of the rise in the concentration of biogenic gases (carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone) in the atmosphere that contribute, along with water vapor, to the so-called ‘greenhouse effect’. Most of the emissions of greenhouse gases have been, and still are, the product of human activities, namely, the excessive use of fossil energy, deforestations in the humid tropics with associated poor land use-management, and wide-scale degradation of soils under crop cultivation and animal/pasture ecosystems. General Circulation Models predict that atmospheric CO2 concentration will probably reach 700 μmol(CO2) mol-1. This can result in rise of Earth’s temperature from 1.5 to over 5°C by the end of this century. This may instigate 0.60-1.0 m rise in sea level, with impacts on coastal lowlands across continents. Crop modeling predicts significant changes in agricultural ecosystems. The mid- and
high-latitude regions might reap the benefits of warming and CO2 fertilization effects via increasing total production and yield of C3 plants coupled with greater water-use efficiencies. The tropical/subtropical regions will probably suffer the worst impacts of global climate changes. These impacts include wide-scale socioeconomic changes, such as degradation and losses of natural resources, low agricultural production, and lower crop yields, increased risks of hunger, and above all waves of human migration and dislocation. Due to inherent cassava tolerance to heat, water stress, and poor soils, this crop is highly adaptable to warming climate. Such a trait should enhance its role in food security in the tropics and subtropics., M. A. El-Sharkawy., and Obsahuje bibliografii
Adding green component to growth light had a profound effect on biomass accumulation in lettuce. However, conflicting views on photosynthetic efficiency of green light, which have been reported, might occur due to nonuniform light sources used in previous studies. In an attempt to reveal plausible mechanisms underlying the differential photosynthetic and developmental responses to green light, we established a new way of light treatment modeled according to the principle of gene "knock out". Lettuce (Lactuca sativa L. var. youmaicai) was grown under two different light spectra, including a wide spectrum of light-emitting diode (LED) light (CK) and a wide spectrum LED light lacking green (480-560 nm) (LG). Total PPFD was approximately 100 µmol(photon) m-2 s-1 for each light source. As compared to lettuce grown under CK, shoot dry mass, photosynthetic pigment contents, total chlorophyll to carotenoids ratio, absorptance of PPFD, and CO2 assimilation showed a remarkable decrease under LG, although specific leaf area did not show significant difference. Furthermore, plants grown under LG showed significantly lower stomatal conductance, intercellular CO2 concentration, and transpiration compared with CK. The plants under CK exhibited significantly higher intrinsic quantum efficiency, respiration rate, saturation irradiance, and obviously lower compensation irradiance. Finally, we showed that the maximum ribulose-1,5-bisphosphate-saturated rate of carboxylation, the maximum rate of electron transport, and rate of triosephosphate utilization were significantly reduced by LG. These results highlighted the influence of green light on photosynthetic responses under the conditions used in this study. Adding green component (480-560 nm) to growth light affected biomass accumulation of lettuce in controllable environments, such as plant factory and Bioregenerative Life Support System., H. Liu, Y. Fu, M. Wang, H. Liu., and Obsahuje bibliografii
Guadua amplexifolia and Guadua angustifolia are the most promising timber substitutes amongst American bamboos due to their outstanding dimensions and structural properties. Despite the commercial potential of these species, there are few studies on the survival and adaptability of juveniles in plantations. The present study dealt with survival, growth, and ecophysiological response of juvenile clonal plants of these species, cultivated in abandoned pastures in Mérida, Venezuela. Survivorship, growth (height and culm diameter), and ecophysiological parameters were monitored the first year during wet and dry seasons. Survival rates were high in both species (95% in G. amplexifolia and 89% in G. angustifolia). Midday leaf water potentials decreased in both species during dry months (-1.28 to-2.72 MPa in G. amplexifolia and-1.67 to-2.37 MPa in G. angustifolia, respectively). Net photosynthetic rates measured during wet [16.57 ± 1.40 and 13.68 ± 2.40 μmol(CO2) m-2 s-1, respectively] and dry seasons [12.19 ± 2.82 and 8.12 ± 1.81 μmol(CO2) m-2 s-1, respectively], demonstrated that G. amplexifolia maintained consistently higher photosynthetic rates compared to G. angustifolia, which could explain the higher growth rates of the former. Similar trends were observed for stomatal conductance, transpiration, water-use efficiency, electron transport rate, and photochemical quenching of PSII. G. angustifolia maintained higher nonphotochemical quenching as well as a higher consumption of electrons per molecule of CO2 fixed, indicating a lower photosynthetic efficiency. The maximal photochemical efficiency of PSII (0.73-0.76) suggested that neither of these species suffered from photoinhibition, despite persistently high radiation and air temperatures at the study site., F. Ely, O. Araque, R. Jaimez., and Obsahuje bibliografii
Soil water and salinity conditions of the riparian zones along the Tarim River, northwest China, have been undergoing alterations due to water use by human or climate change, which is expected to influence the riparian forest dominated by an old poplar, Populus euphratica. To evaluate the effects of such habitat alterations, we examined photosynthetic and growth performances of P. euphratica seedlings across experimental soil water and salinity gradients. Results indicated that seedlings were limited in their physiological performance, as evidenced by decreases in their height and biomass, and the maximal quantum yield of photosystem II (PSII) photochemistry (Fv/Fm), the effective quantum-use efficiency of PSII (Fv′/Fm′), and photochemical quenching (qP) under mild (18% soil water content, SWC; 18.3 g kg-1 soil salt content, SSC) and moderate (13% SWC, 22.5 g kg-1 SSC) water or salinity stress. However, seedlings had higher root/shoot ratio (R/S), increased nonphotochemical quenching (NPQ), and water-use efficiency (WUE) relative to control under such conditions. Under severe (8% SWC, 27.9 g kg-1 SSC) water or salinity stress, P. euphratica seedlings had only a fifth of biomass of those under control conditions. It was also associated with damaged PSII and decreases in WUE, the maximal net photosynthetic rate (P Nmax), light-saturation point (LSP), and apparent quantum yield (α). Our results suggested that the soil conditions, where P. euphratica seedlings could grow normally, were higher than ∼13% for SWC, and lower than ∼22.5 g kg-1 for SSC, the values, within the seedlings could acclimate to water or salinity stress by adjusting their R/S ratio, improving WUE to limit water loss, and rising NPQ to dissipate excessive excitation energy. Once SWC was lower than 8% or SCC higher than ∼28 g kg-1, the seedlings suffered from the severe stress. and J. Y. Li ... [et al.].
In this study, we questioned whether ground-level ozone (O3) induces hormesis in Japanese larch (Larix kaempferi) and its hybrid F1 (L. gmelinii var. japonica × L. kaempferi). In order to answer the question, we exposed seedlings of both taxa to four O3 treatments [ranging from ≈10 to 60 nmol(O3) mol-1] in open-top chambers for two consecutive growing seasons. We found a hormetic response in maximum photosynthetic rate (PNmax) at 1700 μmol(CO2) mol-1 and maximum rates of carboxylation (Vcmax) and electron transport (Jmax) in both larches. Stimulation of PNmax, Vcmax, and Jmax did not lead to suppressed plant productivity in Japanese larch, which followed a stress-tolerant strategy, but it did lead to suppressed plant productivity in hybrid larch which followed a competitive strategy. These findings are the first to suggest that stimulation of physiological functions by low O3 exposures may have negative consequences for larch reproduction., T. Sugai, D.-G. Kam, E. Agathokleous, M. Watanabe, K. Kita, T. Koike., and Obsahuje bibliografii
Seedlings from four provenances of Jatropha curcas were subjected to 80, 50, and 30% of soil field capacity in potted experiments in order to study their responses to water availability. Our results showed that with the decline of soil water availability, plant growth, biomass accumulation, net photosynthetic rate, stomatal conductance (gs), and transpiration rate (E) decreased, whereas leaf carbon isotope composition (δ13C), leaf pigment contents, and stomatal limitation value increased, while maximal quantum yield of PSII photochemistry was not affected. Our findings proved that stomatal limitation to photosynthesis dominated in J. curcas under low water availability. The increase of δ13C should be attributed to the decrease in gs and E under the lowest water supply. J. curcas could adapt to low water availability by adjusting its plant size, stomata closure, reduction of E, increasing δ13C, and leaf pigment contents. Moreover, effects of provenance and the interaction with the watering regime were detected in growth and many physiological parameters. The provenance from xeric habitats showed stronger plasticity in the plant size than that from other provenances under drought. The variations may be used as criteria for variety/provenance selection and improvement of J. curcas performance., C. Y. Yin, X. Y. Pang, A. D. Peuke, X. Wang, K. Chen, R. G. Gong., and Seznam literatury