The short-term acclimation (10-d) of Norway spruce [Picea abies (L.) Karst] to elevated CO2 concentration (EC) in combination with low irradiance (100 μmol m-2 s-1) resulted in stimulation of CO2 assimilation (by 61 %), increased total chlorophyll (Chl) content (by 17 %), significantly higher photosystem 2 (PS2) photochemical efficiency (Fv/Fm; by 4 %), and reduced demand on non-radiative dissipation of absorbed excitation energy corresponding with enhanced capacity of photon utilisation within PS2. On the other hand, at high cultivation irradiance (1 200 μmol m-2 s-1) both Norway spruce and spring barley (Hordeum vulgare L. cv. Akcent) responded to EC by reduced photosynthetic capacity and prolonged inhibition of Fv/Fm accompanied with enhanced non-radiative dissipation of absorbed photon energy. Norway spruce needles revealed the expressive retention of zeaxanthin and antheraxanthin (Z+A) in darkness and higher violaxanthin (V) convertibility (yielding even 95 %) under all cultivation regimes in comparison with barley plants. In addition, the non-photochemical quenching of minimum Chl a fluorescence (SV0), expressing the extent of non-radiative dissipation of absorbed photon energy within light-harvesting complexes (LHCs), linearly correlated with V conversion to Z+A very well in spruce, but not in barley plants. Finally, a key role of the Z+A-mediated non-radiative dissipation within LHCs in acclimation of spruce photosynthetic apparatus to high irradiance alone and in combination with EC was documented by extremely high SV0 values, fast induction of non-radiative dissipation of absorbed photon energy, and its stability in darkness. and I. Kurasová ... [et al.].
Changes in the pools of carotenoids and protochlorophyll(ide) were investigated in etiolated cucumber cotyledons treated with norflurazon (NF) and an experimental herbicide KC 6361 (KC). Both the NF- and the KC-treated tissues considerably accumulated the colourless carotenes phytoene and phytofluene with a concomitant depletion of the coloured carotenoids lutein and β-carotene in darkness. However, the profiles of changes in chlorophylls (Chls) and carotenoids were different for the two herbicides. The plants were also influenced by the photosynthetic photon flux densities (PPFD's), with a more pronounced decline of Chl under high PPFD than under low PPFD. The ratios of protochlorophyll (PChl)/protochlorophyllide (PChlide) were greatly altered due to a decrease and an increase of PChl in the NF- and the KC-treated etiolated tissues, respectively, whereas the PChlide content was not significantly influenced by the inhibitors. Large increase of PChls in the KC-treated tissues seems to derive from the binding of accumulated geranylgeraniol (GG) equivalents, through carotenogenic inhibition, to PChlide. Therefore, the alterations of PChl and PChlide occurring under disturbed carotenogenesis may suggest an interaction between the biosynthetic pathways of Chls and carotenoids. In addition, the great proportion of PChl GG and PChl dihydro-GG in the KC-treated tissues implies that PChl formation is regulated at the level of hydrogenation. and S. Jung ... [et al.].
We compared the responses of wild type (WT) and three mutants including npq1 (lutein-replete and violaxanthin deepoxidase-deficient), lut2 (lutein-deficient), and lut2-npq1 (double mutant) to high irradiance (HI, 2 000 μmol m-2 s-1) at both low (LT, 5 °C) and room (25 °C) temperature. Xanthophyll-dependent energy dissipation was highest in the WT, followed by the lut2, npq1, and npq1-lut2. At 25 °C the relative stress tolerance expressed by Fv/Fm was consistent with the energy dissipation capacity for the first 2 h of treatment. After 3-4 h, the Fv/Fm levels in lut2 and npq1 converged. Under combined LT and HI the relative tolerance sequence was in contrast to the energy dissipation capacity being WT > npq1> lut2 > lut2-npq1. There were little or no significant change in the contents of xanthophylls and carotenes or the chlorophyll (Chl) a/b ratio in any of the materials. Thus lutein (L) substitution possibly alters the conformation/organisation of L binding proteins to enhance damage susceptibility under HI at LT. The enhanced vulnerability is not compensated for the energy dissipation capacity in the lut2 background at LT. and Chang-Lian Peng, A. M. Gilmore.
In leaves of four tomato (Lycopersicon esculentum Mill.) cultivars (Red Cloud, Floradade, Peto 95, and Scorpio) the contents of chlorophyll (Chl) (a+b), Chl a, and β-carotene decreased due to 100 mM NaCl treatment as compared with those of controls. The contents of soluble sugars and total saccharides were significantly increased in leaves of NaCl-treated plants, but the starch content was not significantly affected. Transmission electron microscopy indicated that in leaves of NaCl-treated plants, the chloroplasts were aggregated, the cell membranes were distorted and wrinkled, and there was no sign of grana and thylakoid structures in chloroplasts. and R. A. Khavari-Nejad, Y. Mostofi.
a1_The effect of a wide range of temperatures (-15 and 60°C) in darkness or under strong irradiation [1,600 μmol(photon) m-2 s-1] on quantum yield of photosystem II photochemistry and xanthophyll cycle pigments was investigated in a tropical fruit crop (Musa sp.) and a temperate spring flowering plant (Allium ursinum L.). In darkness within the nonlethal thermal window of A. ursinum (from -6.7 to 47.7°C; 54.5 K) and of Musa sp. (from -2.2°C to 49.5°C; 51.7 K) maximal quantum yield of PSII photochemistry (Fv/Fm) was fairly unaffected by temperature over more than 40 K. At low temperature Fv/Fm started to drop with ice nucleation but significantly only with initial frost injuries (temperature at 10% frost damage; LT10). The critical high temperature threshold for PSII (Tc) was 43.8°C in A. ursinum and 44.7°C in Musa sp. Under strong irradiation, exposure to temperatures exceeding the growth ones but being still nonlethal caused photoinhibition in both species. Severity of photoinhibition increased with increasing distance to the growth temperature range. ΔF/Fm′ revealed distinctly different optimum temperature ranges: 27-36°C for Musa sp. and 18-27°C for A. ursinum exceeding maximum growth temperature by 2-7 K. In both species only at temperatures > 30°C zeaxanthin increased and violaxanthin decreased significantly. At nonlethal low temperature relative amounts of xanthophylls remained unchanged. At temperatures > 40°C β-carotene increased significantly in both species. In Musa sp. lutein and neoxanthin were significantly increased at 45°C, in A. ursinum lutein remained unchanged, neoxanthin levels decreased in the supraoptimal temperature range. In darkness, Fv/Fm was highly temperature-insensitive in both species., a2_Under strong irradiation, whenever growth temperature was exceeded, photoinhibition occurred with xanthophylls being changed only under supraoptimal temperature conditions as an antiradical defence mechanism., A. Dongsansuk, C. Lütz, and G. Neuner., and Obsahuje bibliografii
Energy transfer of aromatic amino acids in photosystem 2 (PS2) core antenna complexes CP43 and CP47 was studied using absorption spectroscopy, fluorescence spectroscopy, and the 0.35 nm crystal structure of PS2 core complex. The energy of tyrosines (Tyrs) was not effectively transferred to tryptophans (Trps) in CP43 and CP47. The fluorescence emission spectrum of CP43 and CP47 by excitation at 280 nm should be a superposition of the Tyr and Trp fluorescence emission spectra. The aromatic amino acids in CP43 and CP47 could transfer their energy to chlorophyll (Chl) a molecules by the Dexter mechanism and the Föster mechanism, and the energy transfer efficiency in CP47 was much higher than that in CP43. In CP47 the Föster mechanism must be the dominant energy transfer mechanism between aromatic amino acids and Chl a molecules, whereas in CP43 the Dexter mechanism must be the dominant one. Hence solar ultraviolet radiation brings not only damages but also benefits to plants. and Y. G. Qu .... [et al.].
A yellow leaf colouration mutant (named ycm) generated from rice T-DNA insertion lines was identified with less grana lamellae and low thylakoid membrane protein contents. At weak irradiance [50 µmol(photon) m-2 s-1], chlorophyll (Chl) contents of ycm were ≈20 % of those of WT and Chl a/b ratios were 3-fold that of wild type (WT). The leaf of ycm showed lower values in the actual photosystem 2 (PS2) efficiency (ΦPS2), photochemical quenching (qP), and the efficiency of excitation capture by open PS2 centres 1 (Fv'/Fm') than those of WT, except no difference in the maximal efficiency of PS2 photochemistry (Fv/Fm). With progress in irradiance [100 and 200 µmol(photon) m-2 s-1], there was a change in the photosynthetic pigment stoichiometry. In ycm, the increase of total Chl contents and the decrease in Chl a/b ratio were observed. ΦPS2, qP, and Fv'/Fm' of ycm increased gradually along with the increase of irradiance but still much less than in WT. The increase of xanthophyll ratio [(Z+A)/(V+A+Z)] associated with non-photochemical quenching (qN) was found in ycm which suggested that ycm dissipated excess energy through the turnover of xanthophylls. No significant differences in pigment composition were observed in WT under various irradiances, except Chl a/b ratio that gradually decreased. Hence the ycm mutant developed much more tardily than WT, which was caused by low photon energy utilization independent of irradiance. and Q. Chen ... [et al.].
The distribution of rare earth elements (REEs) in the fern Dicranopteris dichotoma Bernh plants from a light rare earth elements mine (LRM) and a non-mining (NM) area in Longnan county of Jiangxi province, China were investigated by means of inductively coupled plasma-mass spectrometry, transmission electron microscopy, and energy-dispersive X-ray microanalysis. The photosynthetic characteristics of D. dichotoma were studied by chlorophyll (Chl) a fluorescence kinetics. Contents of REEs in the lamina and the root of D. dichotoma were higher than those in soils, and were mainly distributed in lamina. A part of them was found in the chloroplast. By comparing with D. dichotoma from NM area, the efficiency of photosystem 2 photochemistry and electron transport rate were significantly enhanced in lamina of the plant from LRM because most of REEs deposits were distributed along cell wall, in vacuole, and in chloroplast. High contents of REEs in lamina did not decrease the photosynthetic activities in LRM plants of D. dichotoma. Besides, D. dichotoma could change its β-carotene content to avoid the damaging effect of high REEs content. and L. F. Wang ... [et al.].
The structural characteristics of the extra-membrane domains and guanidine hydrochloride-induced denaturation of photosystem 2 (PS2) core antenna complexes CP43 and CP47 were investigated using fluorescence emission and circular dichroism (CD) spectra. The extra-membrane domains of CP43 and CP47 possessed a certain degree of secondary and tertiary structure and not a complete random coil conformation. The tertiary structure and the chlorophyll (Chl) a microenvironment of CP47 were more sensitive to guanidine hydrochloride (GuHCl) than that of CP43. Changes in energy transfer from β-carotene to Chl a corresponded well to changes in the tertiary structure while their correlation with changes in the secondary structure was rather poor. Unlike most of water-soluble proteins, both CP43 and CP47 are partly resistant to denaturation induced by guanidine hydrochloride (GuHCl); the denaturation of CP43 or CP47 is not a two-state process. Those features most probably reflect their character as intrinsic membrane proteins. and Y.-G. Qu ... [et al.].