Monitoring some parameters would help to overcome the difficulties that can affect in vitro-grown plants during the crucial step of their acclimatization. Thus, after the determination of net photosynthesis and other parameters during acclimatization of in vitro-grown olive plantlets, we concluded that three months after the transfer to ex vitro, the in vitro-grown olive plants become well acclimated. In fact, even though the net photosynthesis, relatively high in vitro, recorded low values after 15 d from the transfer, it reverted back to its standard rates after 180 d of acclimatization. Transpiration and stomatal conductance first increased significantly with a maximum of 6.22 mmol(H2O) m-2 s-1 and 1.8 mmol(H2O) m-2 s-1, respectively, but they regressed to very low values after 180 d of acclimatization. Some changes in the leaf anatomy were also observed; the reduction of stomata density and inversely, the increase of trichome density, especially on the abaxial side of the leaves, were observed., A. Chaari-Rkhis, M. Maalej, A. Chelli-Chaabouni, L. Fki, N. Drira., and Obsahuje seznam literatury
Three-month-old mulberry (Morus alba L.) cultivars (salt tolerant cv. S1 and salt sensitive cv. ATP) were subjected to different concentrations of NaCl for 12 d. Leaf area, dry mass accumulation, total chlorophyll (Chl) content, net CO2 assimilation rate (PN), stomatal conductance (gs), and transpiration rate (E) declined, and intercellular CO2 concentration (Ci) increased. The changes in these parameters were dependent on stress severity and duration, and differed between the two cultivars. The tolerant cultivar showed a lesser reduction in PN and gs coupled with a better Ci and water use efficiency (WUE) than the sensitive cultivar. and S. Giridara Kumar ... [et al.].
Due to anthropogenic influences, solar UV-B irradiance at the earth's surface is increasing. To determine the effects of enhanced UV-B radiation on photosynthetic characteristics of Prunus dulcis, two-year-old seedlings of the species were submitted to four levels of UV-B stress, namely 0 (UV-Bc), 4.42 (UV-B1), 7.32 (UV-B2) and 9.36 (UV-B3) kJ m-2 d-1. Effects of UV-B stress on a range of chlorophyll (Chl) fluorescence parameters (FPs), Chl contents and photosynthetic gas-exchange parameters were investigated. UV-B stress promoted an increase in minimal fluorescence of
dark-adapted state (F0) and F0/Fm, and a decrease in variable fluorescence (Fv, Fv/Fm, Fv/F0 and F0/Fm) due to its adverse effects on photosystem II (PSII) activity. No significant change was observed for maximal fluorescence of dark-adapted state (Fm). Enhanced UV-B radiation caused a significant inhibition of net photosynthetic rate (PN) at UV-B2 and UV-B3 levels and this was accompanied by a reduction in stomatal conductance (gs) and transpiration rate (E). The contents of Chl a, b, and total Chl content (a+b) were also significantly reduced at increased UV-B stress. In general, adverse UV-B effects became significant at the highest tested radiation dose 9.36 kJ m-2 d-1. The most sensitive indicators for UV-B stress were Fv/F0, Chl a content and PN. Significant P<0.05 alteration in these parameters was found indicating the drastic effect of UV-B radiation on P. dulcis. and A. Ranjbarfordoei ... [et al.].
Stressful environments such as salinity, drought, and high temperature (heat) cause alterations in a wide range of physiological, biochemical, and molecular processes in plants. Photosynthesis, the most fundamental and intricate physiological process in all green plants, is also severely affected in all its phases by such stresses. Since the mechanism of photosynthesis involves various components, including photosynthetic pigments and photosystems, the electron transport system, and CO2 reduction pathways, any damage at any level caused by a stress may reduce the overall photosynthetic capacity of a green plant. Details of the stress-induced damage and adverse effects on different types of pigments, photosystems, components of electron transport system, alterations in the activities of enzymes involved in the mechanism of photosynthesis, and changes in various gas exchange characteristics, particularly of agricultural plants, are considered in this review. In addition, we discussed also progress made during the last two decades in producing transgenic lines of different C3 crops with enhanced photosynthetic performance, which was reached by either the overexpression of C3 enzymes or transcription factors or the incorporation of genes encoding C4 enzymes into C3 plants. We also discussed critically a current, worldwide effort to identify signaling components, such as transcription factors and protein kinases, particularly mitogen-activated protein kinases (MAPKs) involved in stress adaptation in agricultural plants., M. Ashraf, P. J. C. Harris., and Obsahuje bibliografii
Glyphosate herbicide caused oxidative stress and exhibited negative effects on photosynthesis and gas exchange of peanut [Arachis hypogaea L. cv. Giza (G) 5 and 6] leaves. We demonstrated that glyphosate caused various morphological symptoms, such as chlorosis, yellowing, and appearance of curly edges in leaves treated with high doses of herbicide in both cultivars; however, the G5 cultivar was more sensitive and showed severer symptoms. Glyphosate lowered photosynthesis and reduced contents of pigments and proteins as well as free amino acids in both cultivars. The gas-exchange parameters, such as photosynthetic (P N) and transpiration rate (E), were highly altered by the glyphosate application. For example, P N and E were reduced by 65 and 61%, respectively, in G5 treated with high dose of glyphosate compared with control. Antioxidant enzymes, such as peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase were induced by both low and high concentrations in the glyphosate-treated leaves. Moreover, the level of lipid peroxidation, indicated by a malondialdehyde content, as well as the hydrogen peroxide content increased in the glyphosate-treated leaves. However, an increase in total antioxidant activity was detected in leaves and this reflected changes in the antioxidant status and accumulation of antioxidants as a defense mechanism against glyphosate toxicity in peanut., D. E. M. Radwan , K. A. Fayez., and Obsahuje seznam literatury
In a glasshouse, Bemisia tabaci infestation largely reduced response of photosynthesis to irradiance and CO2 concentration of Mikania micrantha compared with the non-infested control (C) ones. The maximum irradiance-saturated photosynthetic rate
(Pmax) and saturation irradiance (SI) of the infested M. micrantha were only 21.3 % and 6.5 % of the C-plants, respectively. B. tabaci infestation led to the reduction of contents of chlorophyll and carotenoids in M. micrantha, which was accompanied with the decrease of actual photosystem 2 (PS2) efficiency (ΦPS2), efficiency of excitation energy capture by open PS2 reaction centres (Fv'/Fm'), electron transport rate (ETR), and photochemical quenching (qP). Moreover, superoxide dismutase and catalase activities significantly decreased while proline and glutathione contents significantly increased in infested M. micrantha. Hence B. tabaci infestation not only induced direct damage of photosynthetic apparatus but also altered the antioxidant enzymes activities in M. micrantha, which might as consequences accelerate senescence of this weed. and L. L. Zhang, D. Z. Wen.
Sunflowers were treated with mixing proportions of NaCl, Na2SO4, NaHCO3, and Na2CO3. Effects of salt and saltalkaline mixed stress on growth, photosynthesis, chlorophyll fluorescence, and contents of inorganic ions and organic acids of sunflower were compared. The growth of sunflower decreased with increasing salinity. The contents of photosynthetic pigments did not decrease under salt stress, but their contents decreased sharply under
salt-alkaline mixed stress. Net photosynthetic rates, stomatal conductance and intercellular CO2 concentration decreased obviously, with greater reductions under salt-alkaline mixed stress than under salt one. Fluorescence parameters showed no significant differences under salt stress. However, maximal efficiency of PSII photochemistry, photochemical quenching coefficient, electron transport rate, and actual PSII efficiency significantly decreased but non-photochemical quenching increased substantially under salt-alkaline mixed stress. Under salt-alkaline mixed stress, sunflower leaves maintained a low Na+- and high K+ status; this may be an important feature of sunflower tolerance to salinity. Analysis of the mechanism of ion balance showed that K+ but not Na+ was the main inorganic cation in sunflower leaves. Our results indicated that the change in organic acid content was opposite to the change of Cl-, and the contribution of organic acid to total charge in sunflower leaves under both stresses decreased with increasing salinity. This may be a special adaptive response to stresses for sunflower. Sunflower under stress conditions mainly accumulated inorganic ions instead of synthesizing organic compounds to decrease cell water potential in order to save energy consumption. and J. Liu, D.-C. Shi.
The Theobroma lethal character Luteus-Pa segregates in a 3:1 ratio, expresses in recessive homozygosis, initially inducing leaf chlorosis and finally provoking seedlings death. The objective of this work was to evaluate gas exchange, chlorophyll fluorescence emission, chemical composition and oxidative stress of wild and mutant seedlings resulting from the crosses Pa 30 × Pa 169 and its reciprocal, aiming to elucidate the seedlings death induced by Luteus-Pa. At 15 day after emergence (DAE) differences began to appear between the wild type and mutant. Mutant seedlings showed: (1) lack of photosynthesis and alterations in chloroplast morphology; (2) lower level of three abundant groups of proteins in leaves; (3) decrease in the content of chloroplastidic pigments (4) decrease in peroxidases activities and increase in leaf polyphenol oxidase activity; (5) decrease in carbohydrate and concentration of some nutrients and low dry mass in all plant parts. In leaves of mutant seedlings of both crosses damages occurred in the system responsible for the photochemical phase of photosynthesis. Variations in growth parameters and subsequent seedling death up to 60 DAE were related to exhaustion of cotyledonary reserves, inactive photosynthetic apparatus and oxidative stress. and B. C. Rehem ... [et al.].
In view of predicted climatic changes for the Mediterranean region, study of high temperature and drought impacts on physiological responses of endangered species regains relevance. In this context, micropropagated plants of Tuberaria major, a critically endangered species, endemic of Algarve, were transferred to a controlled-environment cabinet with day/night temperatures set at 25/18°C (Reference) or 32/21°C (HT). After 15 days of HT acclimation, some plants were subjected to progressive drought followed by rewatering. The enhancement of temperature alone did not affect water relations and photosynthetic rates (PN) but the stomatal conductance (gs) exhibited a 3-fold increase in comparison with reference plants. The maximum quantum yield of photosystem (PS) II (Fv/Fm), the effective quantum yield of PSII photochemistry (ΦPSII), carotenoid (Car) and anthocyanin content enhanced, whereas the quantum yields of regulated (ΦNPQ) and nonregulated (ΦNO) energy dissipation decreased. Drought combined with HT reduced predawn leaf water potential to values of about -1.3 MPa, which had adverse effects on gas exchange and PSII activity. Values of PN and gs were 71 and 79% lower than those of HT plants. An impairment of photochemical activity was also observed: the decrease in ΦPSII and the increase of ΦNPQ. However, an irreversible photoinhibitory damage had not occurred. Carotenoid and anthocyanin content remained elevated and soluble sugars (SS) increased twice, whereas proline and MDA accumulation was not detected. On the first 24 h after water-stress relief, gs, PN, ΦPSII, and ΦNPQ did not recover, but SS returned to the reference level. Overall, T. major acquired an adequate capacity for a protection against the development of oxidative stress during drought and water recovery under HT. These findings suggest that T. major is prepared to deal with predicted climate changes., M. L. Osório, J. Osório, A. Romano., and Obsahuje bibliografii
a1_Leaf traits and physiology are species-specific and various with canopy position and leaf age. Leaf photosynthesis, morphology and chemistry in the upper and lower canopy positions of Pinus koraiensis Sieb. et Zucc and Quercus mongolica Fisch. ex Turoz in broadleaved Korean pine forest were determined in September 2009. Canopy position did not significantly affect light-saturated photosynthetic rate based on unit area (P area) and unit dry mass (P mass), apparent quantum yield (α), light compensation point (LCP), light saturation point (LSP); total nitrogen (Nm), phosphorus (Pm), carbon (Cm), and chlorophyll content (Chlm) per unit dry mass; leaf dry mass per unit area (LMA) and photosynthetic nitrogen-use efficiency (PNUE) for P. koraiensis current-year needles and Q. mongolica leaves. While in P. koraiensis one-year-old needles, P area, P mass, α and LCP in the upper canopy were lower than those in the lower canopy. The needles of P. koraiensis had higher Cm and LMA than leaves of Q. mongolica, but P mass, Chlm and PNUE showed opposite trend. There were no differences in P area, LSP, Nm, and Pm between the two species. Needle age significantly influenced photosynthetic parameters, chemistry and LMA of P. koraiensis needles except LCP, LSP and Cm. In contrast to LMA, P area, P mass, Nm, Pm, Chlm, and PNUE of one-year-old needles were significantly lower than those of current-year needles for P. koraiensis. The negative correlations between LMA and
P mass, Nm, Pm, Chlm, and positive correlations between P mass and Nm, Pm, Chlm were found for P. koraiensis current-year needles and Q. mongolica leaves., a2_ Our results indicate that leaf nitrogen and phosphorus contents and nutrient absorption from soil are similar for mature P. koraiensis and Q. mongolica growing in the same environment, while difference in carbon content between P. koraiensis and Q. mongolica may be attributed to inherent growth characteristics., X. B. Cheng ... [et al.]., and Obsahuje bibliografii