The influence of drought stress (DS) upon whole-plant water content, water relations, photosynthesis, and water-use efficiency of Hibiscus rosa-sinensis cv. Leprechaun (Hibiscus) plants at three levels of potassium (K) nutritional status were determined after a 21-d gradually imposed DS treatment. Compared to K-deficient plants, adequate K supply improved the leaf water content (LWC) and leaf water relations of Hibiscus by decreasing the Ψ π, and generally sustained rates of net photosynthesis (PN) and transpiration (E), and stomatal conductance (gs), both in DS and non-DS plants. In K-deficient Hibiscus, LWC, turgor potential (Ψ P), and PN, E, and gs as well as instantaneous water-use efficiency, WUE (PN/E) were consistently lower, compared to K-sufficient plants. Carbon isotope discrimination (Δ) was lower (i.e. longterm WUE was greatest) in DS than non-DS plants, but K had no effect on Δ during the 21-d drought treatment period under glasshouse conditions. However, the trend in the Δ value of DS plants suggests that Δ could be a useful index of the response of Hibiscus to DS under glasshouse growing conditions. Thus the incorporation of a properly controlled fertilization regime involving sufficient levels of K can improve the acclimation of PN to low Ψleaf, increase PN/E of Hibiscus, and may have potential benefit for other woody plants species. and J. N. Egilla, F. T. Davies Jr., T. W. Boutton.
We investigated the strategies of four co-occurring evergreen woody species Quercus ilex, Quercus coccifera, Pinus halepensis, and Juniperus phoenicea to cope with Mediterranean field conditions. For that purpose, stem water potential, gas exchange, chlorophyll (Chl) fluorescence, and Chl and carotenoid (Car) contents were examined. We recognized two stress periods along the year, winter with low precipitation and low temperatures that led to chronic photoinhibition, and summer, when drought coincided with high radiation, leading to an increase of dynamic photoinhibition and a decrease of pigment content. Summer photoprotection was related to non-photochemical energy dissipation, electron flow to alternative sinks other than photosynthesis, decrease of Chl content, and proportional increase of Car content. Water potential of trees with deep vertical roots (Q. coccifera, Q. ilex, and P. halepensis) mainly depended on precipitation, whereas water potential of trees with shallow roots (J. phoenicea) depended not only on precipitation but also on ambient temperature. and F. J. Baquedano, F. J. Castillo.
Maize (Zea mays) seedlings were exposed for 6 h to strong irradiance (1 000 μmol m-1 s-1 of PPFD) at 5, 12, 17, or 25 °C, followed by an exposure to the darkness for 6 h at 22 °C. Leaf chlorophyll fluorescence, net photosynthetic rate (PN), and the amount of superoxide radicals (O2-⋅) in relation to chilling-induced photoinhibition were investigated. During the photophase, a good correlation (r=-0.879) was observed between ΦPS2 (relative quantum efficiency of PS2 electron transport) and the amount of O2-⋅. Treatment with exogenous O2-⋅ reduced the PN and ΦPS2 as the chilling stress did, that was inhibited by specific scavenger of O2-⋅. Hence chilling-induced photoinhibition might be due to the production of O2-⋅. In contrast, in the dark period, PN and ΦPS2 of the seedlings treated with the exogenous O2-⋅ were enhanced, but they were inhibited by the specific scavenger of O2-⋅, showing the photoprotective role of O2-⋅ in the recovery phase. Furthermore, in terms of the effect of exogenous O2-⋅ on the xanthophyll cycle, the O2-⋅ production suggested a promotion effect for the de-epoxidation of violaxanthin during the photophase, the epoxidation of zeaxanthin at the dark stage, and the increase of the xanthophyll pool both in the photophase and dark phase, resulting in an enhancement of the ability of non-photochemical quenching to avoid or alleviate the damage to photosynthetic apparatus. and D. Ke, G. Sun, Y. Jiang.
Lichen thalli were exposed to 4 regimes differing in irradiance and duration of irradiation. Photosynthetic efficiency of thalli was monitored by chlorophyll fluorescence parameters and xanthophyll cycle analysis. Maximal quantum yield of photosystem 2 (FV/FM) decreased gradually with time in long-term treatment. The effect of additional short-term high irradiance (HI) treatment applied each 24 h was not significant. Nevertheless, short-term HI applied repeatedly on thalli kept in the dark led to a significant decrease of FV/FM. Non-photochemical quenching recorded during the long-term treatment corresponded to the content of zeaxanthin (Z). In short-term treatment, however, proportion of Z (and antheraxanthin) to total amount of xanthophyll cycle pigments recovered to the initial values every 24 h after each repeated short-term HI event in thalli kept in dark. Thus duration of irradiation rather than irradiance and frequency of HI events is important for a decrease in primary photosynthetic processes in wet thalli of Lasallia pustulata. Rapidly responding photoprotective mechanisms, such as conversion of xanthophyll cycle pigments, are involved mainly in short-term irradiation events, even at HI. and M. Barták ... [et al.].
This study presents for the first time in detail two manuscripts dealing with the beginnings of the Unitas Fratrum which are in the holdings of the Benedictine Library in Seitenstetten in Austria. Manuscript 72, dating from the beginning of the nineties of the 15th century, contains Latin translations of five letters written by the Czech Brethren to Jan Rokycana from 1489, which have been unknown till now and excerpts from five introductory chapters of the Síť víry (The Net of Faith) by Petr Chelčický, also translated into Latin in 1477. Manuscript 302 contains a copy of the record of an interrogation of four prominent Brethren in Kłodzko in 1480. This article indicates the possibilities of studying these texts, focusing on three main points: on their possible contribution to text tradition research, on research of the circumstances of the origin of their translations, and on the person of the scribe who made the collection. From the possible persons the inquisitor Jindřich Institoris has been excluded as his autograph doesn´t correspond with the writing of the scribe being looked for.
Dynamic changes of neoxanthin (NEO), violaxanthin (VIO), anteraxanthin (ANT), zeaxanthin (ZEA), chlorophyll (Chl) a, Chl b, α-carotene, β-carotene, and their behaviour under increasing duration of high irradiance (HI) were investigated in the soybean hypocotyl callus culture. The calli were induced on solid (1.1 % agar) MS medium (pH 5.8) supplemented with 4.52 μM 2,4-D, 2.32 μM kinetin, and 3 % sucrose. After 30 d of culture, the green calli were irradiated with "white light" (133W m-2) for 0, 3.5, and 24 h. HPLC profiles were separated on a C18 column. With increasing duration of HI, the content of total carotenoids (Cars) increased, but the ratio of Chl a+b/Cars decreased. With lengthening the duration of HI, there was induction of ZEA. Contents of ANT, α-carotene, and β-carotene remained nearly constant, but ratio of ZEA/Chl a+b increased with lengthening the HI duration. and D. M. Pandey, K. H. Kim, U. D. Yeo.
Efficient degradation of damaged D1 during the repair of PSII is carried out by a set of dedicated FtsH proteases in the thylakoid membrane. Here we investigated whether the evolution of FtsH could hold clues to the origin of oxygenic photosynthesis. A phylogenetic analysis of over 6000 FtsH protease sequences revealed that there are three major groups of FtsH proteases originating from gene duplication events in the last common ancestor of bacteria, and that the FtsH proteases involved in PSII repair form a distinct clade branching out before the divergence of FtsH proteases found in all groups of anoxygenic phototrophic bacteria. Furthermore, we showed that the phylogenetic tree of FtsH proteases in phototrophic bacteria is similar to that for Type I and Type II reaction centre proteins. We conclude that the phylogeny of FtsH proteases is consistent with an early origin of photosynthetic water oxidation chemistry., S. Shao, T. Cardona, P. J. Nixon., and Obsahuje bibliografické odkazy
In the xantha1 (xan1) mutant of sunflower (Helianthus annuus L.), the effects on organ anatomy and seedling growth did correlate to the alteration of chloroplast biogenesis. The xan1 seedlings grown under 165 µmol(photon) m-2 s-1 revealed a severely altered chloroplast ultrastructure in cotyledons and leaves. Cross-sections or clarified tissues of the xan1 cotyledons did not show evident alterations with respect to normal cotyledons suggesting that the impairment of chloroplast biogenesis has negligible consequences on embryonic leaves. By contrast, the analysis of xan1 leaves showed that the defects in chloroplast biogenesis were correlated to a drastic reduction of organ size and to a clear enhancement of the trichome growth. The differentiation of palisade and spongy parenchyma in cotyledons and leaves of the xan1 mutant was normal but both organs displayed a drastic reduction in the plastid number with respect to wild type. In addition, xan1 hypocotyls showed a reduced development of the main vascular bundles in comparison with normal seedlings and an undersized central cylinder of the primary root. The exogenous supply of sucrose was not sufficient to revert in vitro the deficit of xan1 growth and the constraints in morphogenetic processes. and M. Fambrini ... [et al.].
Commercial chambers for in vivo gas exchange are usually designed to measure on vascular plants, but not on cryptogams and other organisms forming biological soil crusts (BSCs). We have therefore designed two versions of a chamber with different volumes for determining CO2 exchange with a portable photosynthesis system, for three main purposes: (1) to measure in situ CO2 exchange on soils covered by BSCs with minimal physical and microenvironmental disturbance; (2) to acquire CO2-exchange measurements comparable with the most widely employed systems and methodologies; and (3) to monitor CO2 exchange over time. Different configurations were tested in the two versions of the chamber and fluxes were compared to those measured by four reference commercial chambers: three attached to two respirometers, and a conifer chamber attached to a portable photosynthesis system. Most comparisons were done on biologically crusted soil samples. When using devices in a closed system, fluxes were higher and the relationships to the reference chambers were weaker. Nevertheless, high correlations between our chamber operating in open system and measurements of commercial respiration and photosynthetic chambers were found in all cases (R2 > 0.9), indicating the suitability of the chamber designed for in situ measurements of CO2 gas exchange on BSCs., M. Ladrón De Guevara, R. Lázaro, J. L. Quero, S. Chamizo, F. Domingo., and Obsahuje bibliografii