Expression of Peroxidases During Seedling Growth in <Emphasis Type="Italic">Ebenus Cretica</Emphasis> L. as Affected by Light and Temperature Treatments

Peroxidase (POD) activity and isoform patterns were investigated during seedling growth (up to 20 days) of Ebenus cretica L. Seeds germinated to approx. 100% after a 24-h imbibition. Seedling growth proceeded smoothly, in both light and dark conditions. No seedling growth was noticed at 4°C. A positive effect of light and increasing temperature (4, 10, 16, 22 and 28°C) on seedlings growth, lignin content and POD activity was observed. Lignin content was 2.5 times higher in seedlings grown under light than in seedlings grown under darkness. Seedlingsȁ9 POD activity was higher in acid pH (5.5) in comparison to neutral pH (7.0). These activities were higher in seedlings grown under darkness than in those grown under light; since additional POD isoforms were expressed in dark conditions. The increase in POD activity was accompanied with the appearance of new POD isoforms correlated with the growth of the seedlings. Four soluble anionic POD isoforms (named A₁, A₂, A₃ and A₄) and three soluble cationic POD isoforms (named C₁, C₂ and C₃) were displayed depending on the treatment and the course of growth. POD isoforms were detected in gel after PAGE. The fast migrating (A₄) isoform, which appeared in the dark-grown seedlings as well as on day 20 at 28°C in the temperature treatment, was separated by DEAE–Sepharose column chromatography. A slow migrating C₁ isoform slightly appeared in both 4 and 10°C temperature treatments and could be related to the low temperature treatments, while A₁, A₂, A₃ and C₂ to the growth stage of seedlings. The expression of seven POD isoforms during seedling growth seems to be related to different developmental events of growth and could be used as useful biochemical markers in the analysis of metabolic regulation in seedling growth of Ebenus cretica.     

Photosystem II reaction centres stay intact during low temperature photoinhibition

Photoinhibition of photosynthesis was studied in intact barley leaves at 5 and 20°C, to reveal if Photosystem II becomes predisposed to photoinhibition at low temperature by 1) creation of excessive excitation of Photosystem II or, 2) inhibition of the repair process of Photosystem II. The light and temperature dependence of the reduction state of Q_A was measured by modulated fluorescence. Photon flux densities giving 60% of Q_A in a reduced state at steady-state photosynthesis (300 mol m^–2s^–1 at 5°C and 1200 mol m^–2s^–1 at 20°C) resulted in a depression of the photochemical efficiency of Photosystem II (F_v/F_m) at both 5 and 20°C. Inhibition of F_v/F_m occurred with initially similar kinetics at the two temperatures. After 6h, F_v/F_m was inhibited by 30% and had reached steady-state at 20°C. However, at 5°C, F_v/F_m continued to decrease and after 10h, F_v/F_m was depressed to 55% of control. The light response of the reduction state of Q_A did not change during photoinhibition at 20°C, whereas after photoinhibition at 5°C, the proportion of closed reaction centres at a given photon flux density was 10–20% lower than before photoinhibition.Changes in the D1-content were measured by immunoblotting and by the atrazine binding capacity during photoinhibition at high and low temperatures, with and without the addition of chloramphenicol to block chloroplast encoded protein synthesis. At 20°C, there was a close correlation between the amount of D1-protein and the photochemical efficiency of photosystem II, both in the presence or in the absence of an active repair cycle. At 5°C, an accumulation of inactive reaction centres occurred, since the photochemical efficiency of Photosystem II was much more depressed than the loss of D1-protein. Furthermore, at 5°C the repair cycle was largely inhibited as concluded from the finding that blockage of chloroplast encoded protein synthesis did not enhance the susceptibility to photoinhibition at 5°C.It is concluded that, the kinetics of the initial decrease of F_v/F_m was determined by the reduction state of the primary electron acceptor Q_A, at both temperatures. However, the further suppression of F_v/F_m at 5°C after several hours of photoinhibition implies that the inhibited repair cycle started to have an effect in determining the photochemical efficiency of Photosystem II.Abbreviations CAP D-threochloramphenicol - F₀ and F ₀ fluorescence when all Photosystem II reaction centres are open in dark- and light-acclimated leaves, respectively - F_m and F _m fluorescence when all Photosystem II reaction centres are closed in dark- and light-acclimated leaves, respectively - F_s fluorescence at steady state - Q_A the primary, stable quinone acceptor of Photosystem II - q_N non-photochemical quenching of fluorescence - q_P photochemical quenching of fluorescence     

Low-temperature limitations of photosynthesis in three tropical Vigna species: A chlorophyll fluorescence study

The temperature-dependence of photosynthesis and chlorophyll (Chl) fluorescence quenching components was studied between 0 and 45°C in three tropical, chilling-sensitive Vigna species and in chilling-tolerant pea. Photosynthesis of the Vigna spp. was approx. 20% more reduced by temperatures between 7 and 30°C than in pea. The latter revealed significant changes in Chl fluorescence parameters at much lower temperature than the Vigna spp. Below 15°C, the reduction state of Q_A increased quickly in pea, while in Vigna already below 30°C, an increase of reduced Q_A was obtained. The analysis of different components of non-photochemical Chl fluorescence quenching (q_N) revealed, that in pea photoinhibitory quenching (q_I) occurred below 13°C. Below ca. 7°C, a sudden breakdown of both q_P and the fast relaxing component of q_N was observed in pea.In Vigna, susceptibility of LHC II phosphorylation or limitation of electron flow by damage to PS I, the PS II reaction centre or the water-splitting system were not responsible for the chilling-sensitivity of photosynthesis between 5 and 30°C. Instead, photosynthesis was gradually limited by an inefficient use of reduction equivalents. This, in turn may increase susceptibilty to photoinhibition, which occurred below 20°C in Vigna. The combined study of q_P and of the different components of q_N allowed the demonstration of the subsequent occurrence of different limiting processes with decreasing temperature in the chilling-sensitive Vigna species.     

A thermostable manganese-containing superoxide dismutase from the thermophilic fungus Thermomyces lanuginosus

A thermostable superoxide dismutase (SOD) from a Thermomyces lanuginosus strain (P134) was purified to homogeneity by fractional ammonium sulfate precipitation, ion-exchange chromatography on DEAE-Sepharose, Phenyl-Sepharose hydrophobic interaction chromatography, and gel filtration on Sephacryl S-100. The molecular mass of a single band of the enzyme was estimated to be 22.4 kDa, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Using gel filtration on Sephacryl S-100, the molecular mass was estimated to be 89.1 kDa, indicating that this enzyme was composed of four identical subunits of 22.4 kDa each. The SOD was found to be inhibited by NaN₃, but not by KCN or H₂O₂, suggesting that the SOD in T. lanuginosus was of the manganese superoxide dismutase type. The SOD exhibited maximal activity at pH 7.5. The optimum temperature for the activity was 55°C. It was thermostable at 50 and 60°C and retained 55% activity after 60 min at 70°C. The half-life of the SOD at 80°C was approximately 28 min and even retained 20% activity after 20 min at 90°C.     

A novel low-temperature active alkaline pectate lyase from Klebsiella sp. Y1 with potential in textile industry

Alkaline pectate lyases are favorable for the textile industry. Here we report the cloning of a pectate lyase gene (pl A), from Klebsiella sp. Y1, and its heterologous expression in Escherichia coli. The full-length pl A consists of 1710 bp and encodes for a 569-amino acid polypeptide including a putative 22-residue signal peptide and a catalytic domain belonging to pectate lyase family 2. The recombinant enzyme (r-PL A) was purified to electrophoretic homogeneity by single-step Ni²⁺-NTA affinity chromatography and showed an apparent molecular weight of ∼60 kDa. The pH and temperature optima of r-PL A were found to be 9.0 and 30–50 °C, respectively. r-PL A was highly active at low temperatures, exhibiting >60% of the maximal activity at 20 °C and >20% activity even at 0 °C. The enzyme was stable in a broad alkaline pH range of 7.0–12.0 for 1 h at 37 °C. The values of K_m(app) and V_max(app) of r-PL A for polygalacturonic acid were 2.47 mg/ml and 11.94 μmol/min/mg, respectively. Compared with the commercial compound pectinase from Novozymes, purified r-PL A showed similar efficacy in reducing the intrinsic viscosity of polygalacturonic acid (68.8% vs. 67.1%) and in bioscouring of jute (7.38% vs. 7.58%). Thus r-PL A is a valuable material for the textile industry.     

General characteristics of thermostable amylopullulanases and amylases from the alkalophilic Bacillus sp. TS-23

An alkalophilic strain of Bacillus sp., designated TS-23, was isolated from a soil sample collected at a hot spring (Tainan, Taiwan). During growth in a medium containing 1% soluble starch as the sole source of carbon, the fermentation broth exhibited both pullulanase and amylase activity. Pullulanase and amylase activities were maximal at 65° C. The pH optima were 8.8 to 9.6 for pullulanase and 7.5 to 9.4 for amylase. Under optimal conditions, a crude preparation hydrolysed pullulan, generating maltotriose as the major product. Strain TS-23 was found to produce five amylases (A_c, A₁, A₂, AP₁, and AP₂), which were visualized by activity staining of proteins that had been separated by native polyacrylamide gel electrophoresis. Both AP₁ and AP₂ had pullulanase activity and A_c, A₁ and A₂ had the ability to adsorb to raw corn-starch. Native corn-starch was partially digested by adsorbed amylases during the course of 12 h at 50° C, with initiation of granular pitting. Further incubation of the reaction mixture resulted in considerable morphological changes in corn-starch granules, and the main soluble products were maltose, maltotriose and higher oligosaccharides.     

Temperature/light dependent development of selective resistance to photoinhibition of photosystem I

Exposure of winter rye leaves grown at 20°C and an irradiance of either 50 or 250 μmol m⁻² s⁻¹ to high light stress (1600 μmol m⁻² s⁻¹, 4 h) at 5°C resulted in photoinhibition of PSI measured in vivo as a 34% and 31% decrease in ΔA₈₂₀/A₈₂₀ (P700⁺). The same effect was registered in plants grown at 5°C and 50 μmol m⁻² s⁻¹. This was accompanied by a parallel degradation of the PsaA/PsaB heterodimer, increase of the intersystem e⁻ pool size as well as inhibition of PSII photochemistry measured as F_v/F_m. Surprisingly, plants acclimated to high light (800 μmol m⁻² s⁻¹) or to 5°C and moderate light (250 μmol m⁻² s⁻¹) were fully resistant to photoinhibition of PSI and did not exhibit any measurable changes at the level of PSI heterodimer abundance and intersystem e⁻ pool size, although PSII photochemistry was reduced to 66% and 64% respectively. Thus, we show for the first time that PSI, unlike PSII, becomes completely resistant to photoinhibition when plants are acclimated to either 20°C/800 μmol m⁻² s⁻¹ or 5°C/250 μmol m⁻² s⁻¹ as a response to growth at elevated excitation pressure. The role of temperature/light dependent acclimation in the induction of selective tolerance to PSI photoinactivation is discussed.     

Estimating the initial reaction velocity of a soluble dehydrogenase in situ

Summary The initial reaction velocities (v _i ) of lactate dehydrogenase in single hepatocytes were determined, by microdensitometry or computer-assisted image analysis, in sections of unfixed mouse liver incubated at 37°C on substrate-containing agarose gel films. They were found to fit the equations v _i =2.82°A and v _i =v+2°A, where v and °A are, respectively, gradients (or steady-state linear velocities) and the intercepts on the absorbance axis of the linear regression lines of the absorbance (A) on incubation time plots for incubation times between 1 and 3 min. Both equations were independent of section thickness between 4 and 14 m. The observed and calculated values of v _i , agreed within 11.5% (n = 71). The validity of the equations for v _i was confirmed by showing that the calculated v _i was proportional to the thickness of the section and hence the amount of enzyme present. Thus, v _i can be determined from measurements of either °A alone or v and °A.     

Responses of florence fennel (Foeniculum vulgare azoricum) seeds to light,temperature and gibberellin A4/7

The percentage and the rate of germination of seeds of three varieties of Florence fennel was higher in the dark than in the light, the high temperature cut-off points being between 27.2 and 29.4°C. The optimum temperature for germination was between 20 and 25°C. Seeds of all three varieties responded to incubation in solutions containing gibberellin A_4/7 mixture (GA_4/7; Regulex), giving higher germination in the light at temperatures from 20 to 30°C. Seeds steeped for 4 h at 25°C or for 24 h at 5°C in GA_4/7 solutions gave a higher percentage and increased rate of emergence as compared with untreated dry seeds, when sown in compost at 25°C; steeping in water alone was also beneficial. In general, drying the treated seeds before sowing reduced the rate but sometimes increased the percentage of germination as compared with seeds sown when still moist. Seeds harvested from secondary umbels of var. Zefa fino germinated better both in the light and dark than those taken from primary umbels.Abbreviations GA_4/7 a commercial mixture of the gibberellins A₄ and A₇ (trade name Regulex)     

Foraging profits and thoracic temperature of honey bees (Apis mellifera)

Summary Body temperature and duration of foraging activities were affected by the concentration of sucrose solution imbibed. When experienced foragers of Apis mellifera arrived at a gravity feeder from the hive, thoracic temperature (T_TH) was independent of sucrose concentration (X = 36.3 °C). While imbibing 40% and 60% (g solute per g of solution) solutions bees maintained T_TH at approximately the same high level as upon arrival, but those imbibing 10%, 20%, and 30% solutions regulated T_TH lower (X = 33.5 °C). All bees departed the feeder for the hive at the same T_TH (X = 36.1 °C). Bees that imbibed 40% and 60% solutions sometimes immediately took flight after imbibition and averaged less than 15 s to takeoff. Time to takeoff was 2–3 times longer for bees that had imbibed 10% and 20% solutions because warmup preceded takeoff. The rate of energy expenditure at T_TH=36.3°C (at 40% and 60% solutions) was 20% greater than that at 33.3°C (at 10%, 20%, and 30% solution). Bees that fed on the highly concentrated solutions regulated T_TH so that rate of net energy gain was enhanced, but bees that fed on less concentrated solutions could have increased rate of net gain by maintaining a higher T_TH which would have reduced time required for takeoff. The latter bees lowered rate of expenditure of their limited energetic costs and thereby lowered short-term net profits in favor of improved long-term contribution to the colony.Abbreviations T _A ambient temperature - T _TH thoracic temperature     

Die Atmung beim KolibriAmazilia fimbriata während des Schwirrfluges bei verschiedenen Umgebungstemperaturen

Zusammenfassung An schwirrenden Kolibris (Amazilia fimbriata fluviatilis, mittleres Gewicht 5,7 g) wurden O₂-Verbrauch, CO₂-Produktion, Atemfrequenz, respiratorische Wasserabgabe und Flügelschlagfrequenz gemessen. Die Versuche wurden bei Temperaturen von 0–35 ° C durchgeführt.Der O₂-Verbrauch im Plug bei Temperaturen über 20 ° C beträgt 4,1 ml O₂/min= 43 ml O₂/g·h, was das 14fache des Basalstoffwechsels ist. Bei Erniedrigung der Umgebungstemperatur nimmt der O₂-Verbrauch kontinuierlich um etwa 6% je 10 ° C zu (Abb. 3). Es wird beim Schwirrflug eine weitgehende Substitution der thermoregulatorisch notwendigen Wärmeproduktion durch die bei der Kontraktion der Flugmuskeln entstehende Wärmemenge angenommen.Es wurde die Atemfrequenz mit rund 280/min bestimmt, das Atemzugvolumen mit 0,63 ml (BTS), die Ventilation mit 0,18 l/min (BTS) und die Sauerstoffausnutzung mit 2,2% errechnet.Die respiratorische Wärmeabgabe beträgt bei Temperaturen bis 20 ° C weniger als 20% der Wärmeproduktion, bei 35 ° C wurde das Maximum von 40% gemessen (Abb. 6). Bei trockener Luft macht die respiratorische Wasserabgabe 2,9–4,6% (0–20 ° C) bzw. rund 11% (bei 35 ° C) des Körpergewichtes pro Stunde aus. Bei 0 ° C gleichen sich Wasserproduktion durch Stoffwechselvorgänge und respiratorische Abgabe, bei allen anderen Temperaturen überwiegt die Abgabe: bei 35 ° C beträgt der Netto verlast 350% der Produktion.

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Respiration in the hummingbirdAmazilia fimbriata during hovering at different ambient temperatures

Summary In hovering hummingbirds (Amazilia fimbriata fluviatilis, mean weight 5.7 g) oxygen consumption, CO₂ production, breathing frequency, respiratory water loss and wing frequency were measured at various environmental temperatures from 0 to 35 ° C.The oxygen consumption above 20 ° C reached 4.1 ml/min = 43 ml/g·hr, and was 14 times the calculated basal rate. Oxygen consumption increased about 6% for a 10 ° C fall in environmental temperature (Fig. 3). During flight the thermoregulatory heat production at low temperatures was largely substituted by the heat that is produced by contraction of the wing muscles.The respiratory frequency was estimated to be 280/min, the tidal volume 0.63 ml (BTS), the ventilation 0.18 1/min (BTS) and the oxygen utilization as 2.2%.The respiratory heat loss at temperatures of 20 ° C and below was less than 20% of the heat production, while at 35 ° C a maximum loss of 40% was reached (Fig. 6). In dry air at 0–20° C the water loss measured 2.9 to 4.5% of body weight per hour while at 35 ° C the loss was 11%. At 0 ° C the respiratory water loss and metabolic water production were equal, but at all other temperatures the loss exceeded production (at 35 ° C the loss exceeded production by 350%).

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Herrn Prof. Dr. Jürgen Aschoff zum 60. Geburtstag gewidmet.

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N.R.C.C. Nr. 12844.     

Thermoperiodic control of stem elongation and endogenous gibberellins in Campanula isophylla

The effect of day/night temperature regimes on stem elongation and on the content of endogenous gibberellins (GAs) in vegetatively propagated plants of Campanula isophylla cv. Hvit have been studied. Compared with a constant temperature regime at 18°C (18/18°C), stem and internode elongation was enhanced significantly by a combination of high day/low night temperature (21/15°C) and inhibited by an opposite regime (15/21°C). Gibberellins A₁, A₁₉, A₄₄, A₅₃, and A₉₇ were identified as endogenous components in Campanula. (GA₉₇ was earlier referred to as 2-OH-GA₅₃.) Quantitative analysis of the endogenous GAs indicates that temperature regimes that stimulate elongation growth are accompanied by an increase in the level of GA₁, GA₁₉, and GA₄₄. On the other hand, in plants grown under conditions that reduced stem elongation growth, there was an increased level of GA₉₇.Abbreviations DIF difference between day temperature and night temperature - GA gibberellin - HPLC high performance liquid chromatography - GC-MS gas chromatography-mass chromatography - SPE solid phase extraction - TMS trimethylsilyl - MSTFA N-methyl-N-TMS-trifluoroacetamide - KRI Kovats retention index - SIM selected ion monitoring - D2 deuterated     

Life history of Euseius scutalis feeding on citrus red mite Panonychus citri at various temperatures

The aim of this study was todetermine the biology and reproductivepotential of Euseius scutalis(Athias-Henriot) (Acari: Phytoseiidae) atvarious temperatures. These data are of valuein relation to mass rearing and the developmentof population dynamics models. The developmenttime, survival and fecundity of E.scutalis were determined at 20, 25 and30 ± 1 °C, 65 ± 10% RH and 16:8photoperiod. Total development times of E.scutalis were 6.7, 4.9 and 4.2 days at 20, 25and 30 ± 1 °C, respectively, using adiet of all life stages of the spider mite Panonychus citri (McGregor) (Acari:Tetranychidae). In general, preoviposition andpostoviposition periods of E. scutaliswere shortened as temperature increased, butthe oviposition period was longer at 25 °C than at 20 and 30 °C. Theshortest survival time of E. scutalis, at30 °C, was 10.1 days, followed by 23.7days and 28.6 days at 20 and 25 °C,respectively. Mated females laid on average1.1, 1.4 and 1.7 eggs per female per day and21.5, 39.7 and 17.1 eggs over their entire lifetime at 20, 25 and 30 °C, respectively.The sex ratios of E. scutalis were2.11/1, 2.24/1 and 2.11/1 female/male at 20, 25and 30 °C, respectively. The intrinsicrate of natural increase (r _m) increasedwith rising temperatures from 0.166 at 20 °C to 0.295 females/female/day at 30 °C. The net reproductive rate (R ₀)was highest at 25 °C (26.03females/female) and lowest at 30 °C(12.95 females/female). Mean generation time(T ₀) was longest at 25 °C (17.50days) and shortest (9.53 days) at 30 °C.     

Temperature dependence of structure, bending rigidity, and bilayer interactions of dioleoylphosphatidylcholine bilayers

X-ray diffuse scattering was measured from oriented stacks and unilamellar vesicles of dioleoylphosphatidylcholine lipid bilayers to obtain the temperature dependence of the structure and of the material properties. The area/molecule, A, was 75.5 Å² at 45°C, 72.4 Å² at 30°C, and 69.1 Å² at 15°C, which gives the area expansivity α_A = 0.0029/deg at 30°C, and we show that this value is in excellent agreement with the polymer brush theory. The bilayer becomes thinner with increasing temperature; the contractivity of the hydrocarbon portion was α_Dc = 0.0019/deg; the difference between α_A and α_Dc is consistent with the previously measured volume expansivity α_Vc = 0.0010/deg. The bending modulus K_C decreased as exp(455/T) with increasing T (K). Our area compressibility modulus K_A decreased with increasing temperature by 5%, the same as the surface tension of dodecane/water, in agreement again with the polymer brush theory. Regarding interactions between bilayers, the compression modulus B as a function of interbilayer water spacing D′_W was found to be nearly independent of temperature. The repulsive fluctuation pressure calculated from B and K_C increased with temperature, and the Hamaker parameter for the van der Waals interaction was nearly independent of temperature; this explains why the fully hydrated water spacing, D′_W, that we obtain from our structural results increases with temperature.     

A thermoluminescence study of Photosystem II back electron transfer reactions in rice leaves – effects of salt stress

The recombination reactions of Photosystem II have been investigated in vivo in rice leaves by using the thermoluminescence (TL) emission technique. Excitation of dark-adapted leaf segments at 0 °C with different number of single turn-over flashes induced the appearance of complex TL glow curves. The mathematical analysis of these curves showed the existence of four TL components: B1-band (temperature maximum, t_max, at 24 °C, originating from S₃Q_B⁻ recombination), B2-band (t_max at 35 °C, from S₂Q_B⁻), AG-band (t_max at 46 °C) and C-band (t_max at 55 °C, from Tyr_D⁺Q_A⁻). Their contributions to the total TL signal were different depending on the number of flashes given. AG-band seems to reflect a special electron transfer from some unknown stroma donor to PS II. Q-band (t_max at 19 °C), originating from S₂Q_A⁻ recombination, was recorded after flashing samples incubated in the presence of DCMU. The recombination halftimes (t_1/2) at 20 °C of S₂Q_A⁻, S₃Q_B⁻, S₂Q_B⁻ and Tyr_D⁺Q_A⁻ were, respectively, 0.8 s, 48 s, 74 s and about 1 h. A sharp AG-band (t_max at 50 °C and t_1/2 of 210 s) could be also observed after illumination of leaves with far-red light and after a dark incubation period of whole plants. Incubation of leaf segments with 0.5 M NaCl abolished the inductions of AG-band by darkness and far-red illumination, significantly decreased Q-band intensity, whereas induced a strong increase in C-band intensity. The possible inhibition of S₂/S₃ formation and quinone oxidation by saline stress are discussed.     

The control by RNA of pyruvate kinase activity in human skeletal muscle

Summary About 25% of total pyruvate kinase activity in human skeletal muscle is associated with the ribonucleoprotein complexes soluble in salt solutions of high ionic strength. These complexes, called form M_B, crystallize readily from 48% saturated ammonium sulfate at pH 5.6.Crystalline preparations represent a heterogenous population of ribonucleoprotein complexes displaying a graduated activity and a variable RNA content. Free protein was not detected in the preparations.Fractionation of crystalline complexes in salt solutions of varying ionic strength and pH, followed by gel filtration on Sephadex G-200 led to the separation of two nucleoprotein fractions with very high specific activity. Fractions containing 30% RNA and 85% RNA respectively revealed a specific activity of 660–670 U/mg protein at 25°C.Pyruvate kinase form M_A was extracted from muscle homogenate with distilled water, purified to homogeneity and crystallized. It contained less than 0.2% RNA and had a specific activity of 270 U/mg. Active ribonucleoprotein complexes gave in double immunodiffusion test the precipitation bands with the anti-M_A sera at the same protein concentration of both antigens, M_B and M_A.Pyruvate kinase M_B with high activity is sensitive to treatment with RNase. Digestion with RNase for 10 min at 25°C diminished the initial specific activity to about one third. Similar residual activity was found in crystalline ribonucleo protein complexes with low RNA content (3.5–20% RNA) which are resistant to further inactivation by RNase.These results implicate the enhancement and control of pyruvate kinase activity by RNA bound to the enzyme.This work was supported by a grant from the Biochemical and Biophysical Committee of Polish Academy of Sciences.     

Chloroplast biogenesis at cold-hardening temperatures. Kinetics of trans-Δ3-hexadecenoic acid accumulation and the assembly of LHCII

Etiolated seedlings developed at cold-hardening temperatures (5°C) exhibited etioplasts with considerable vesiculation of internal membranes compared to etioplasts developed at 20°C regardless of the osmotic concentration employed during sample preparation. This vesiculation disappeared during exposure to continuous light at 5°C. This transformation of 5°C and 20°C etioplasts to chloroplasts under continuous light at 5° and 20°C respectively proceeded normally with the initial development of non-appressed lamellae and the subsequent appearance of granal stacks. However, chloroplasts developed at 5°C exhibited fewer lamellae per granum than chloroplasts developed at 20°C.Although the polypeptide complements of etioplasts and chloroplasts developed at 5° or 20°C were not significantly different, monomeric light harvesting complex (LHCII₃) was assembled into oligomeric light harvesting complex (LHCII₁) during chloroplast biogenesis at 20°C (oligomer:monomer =1.8) whereas monomeric LHCII predominated at 5°C (oligomer:monomer =0.3). Low temperature fluorescence emission spectra of isolated thylakoids indicated that both the F₆₈₅/F₇₃₅ and F₆₉₅/F₇₃₅ were significantly higher after greening at 5°C than at 20°C. In addition, chloroplast biogenesis at 5°C was associated with a low ratio of trans-₃-hexadecenoic acid (0.5) in phosphatidylglycerol whereas at 20°C biogenesis was associated with a high ratio (1.6). Comparative kinetics indicated that the maximization of the trans-₃-hexadecenoic acid level precedes the assembly of monomeric LHCII into oligomeric LHCII during biogenesis at 20°C. It is suggested that low developmental temperatures modulate the assembly of LHCII by reducing the trans-₃-hexadecenoic acid content of phosphatidylglycerol such that monomeric or some intermediate form of LHCII predominates.Abbreviations RH Cold-hardened rye - RNH Non-hardened rye - EF Exoplasmic freeze fracture face - Chl Chlorophyll - LHCII Light harvesting Chl a/b protein complex - LHCII₁ Oligomeric form - LHCII₂ Dimeric form - LHCII₃ Monomeric form - CPl Chl a-protein complex associated with photosystem I - CPa Chl a-protein comples associated with photosystem II - FP Free pigment - PSI Photosystem I - PSII Photosystem II - Trans-16:1 Trans-₃-hexadecenoic acid - 16:0 Palmitic acid - 18:3 Linolenic acid - PG Phosphatidylglycerol - PC Phosphatidylcholine - PE Phosphatidylethanolamine - SL Sulfolipid - DGDG Digalactosyldiacylglycerol - MGDG Monogalactosyldiacylglycerol - SDS Sodium dodecyl sulfate - PAGE Polyacrylamide gel electrophoresis - PLB Prolamellar body - A Angstrom - DOC deoxycholate     

Dormancy in peach (Prunus persica L.) flower buds

Morphological studies were carried out with peach flower buds collected monthly in 1989 and 1990, from two months before leaf fall (7 March) until two to three weeks before bloom (7/8 August). Chilled (2–4°C for 30 days) and unchilled buds were exposed to 20 to 25°C, 100% RH and continuous light. Gibberellin A₃ (3 ng or 30 ng) was applied to some of the non-chilled cuttings at three days intervals. Then, 12, 19, and 26 days after they were planted, the buds were sampled and processed for histological studies. Cultured flower buds (chilled or unchilled) had accelerated anther and gynoecium morphogenesis after 12 days under controlled conditions, compared to buds processed immediately after collection from the field. Chilling treatment augmented the bud culture effect, while Gibberellin A₃ applications to the excised buds retarded bud morphogenesis to a stage comparable to that of buds collected directly from the field. This, suggests that the comparatively high levels of Gibberellin A_1/3 we previously found in mid winter [15, 18] could be at least one of the factors that controls floral bud dormancy by retarding anther and gynoecium development.     

Seasonal variation in the physical properties of agar and biomass of Gracilaria sp. (chorda type) from Tosa Bay,southern Japan

Plants of Gracilaria sp.(chorda type), which grow along the coast of Uranouchi Inlet in Tosa Bay, southern Japan, showed the highest biomass in the summer (26 °C to 31 °C) and spring season (15.1 °C to 24.9 °C). Maximum biomass was 6952 g m^–2 in July, but gradually decreased in the autumn (30.5 °C in September to 20 °C in November) and winter (19.5 °C in December to 14.9 °C in February). Variation in yields and gel strength of the agars, were shown to depend on the time in the season. After alkali treatment (5% NaOH, 2 h) at three different temperatures (70, 80, and 90 °C), the agars showed gel strengths essentially that of commercial grade agars, with the best gel obtained at 80 °C. Maximum gel strength (1455 g cm^–2 of 1.5% agar gel) occurred in winter when the biomass and agar yield were low. Minimum gel strength was in spring. Gel strength was inversely correlated with agar yield, but was positively correlated with apparent viscosity. Maximum viscosity was 40 cP. in December. Gelling temperatures, pH of 1.5% agar gel, and moisture content in agars showed little variation.     

Relationships between position on the parent plant and germination characteristics of seeds of parsley (Petroselinium crispum Nym.)

The percentage germination of seeds of parsley cv. Imperial Curled was higher in the light than in the dark, the high temperature limits for germination being 30 and 28°C for light and dark respectively. At the higher temperatures, the germination rate was slower in the dark. At 30°C, treatment with a gibberellin A_4/7 mixture at 2 × 10^–4 M partially alleviated the inhibiting effect of darkness on the germination percentage. Pre-incubation of parsley seeds at 35°C in the dark for 30 h increased the rate, but decreased the percentage, of germination of seeds incubated at 15°C in the light. Germination and seedling emergence studies were made on seed harvested from four different umbel positions. Although heavier seeds were produced from primary umbels than from other umbel orders, they were less viable as measured by seedling emergence in the glasshouse. The rate of emergence was decreased with increasing umbel order i.e. with later seed development: this was reflected in subsequent seedling weights, with seedlings from quarternary umbel seeds being about half the weight of those from primary umbel seeds. The upper temperature limit for dark germination was only slightly affected by umbel order, with quarternary umbel seeds being the most thermo-inhibited.Abbreviations BA N⁶-benzyladenine - GA_4/7 a mixture of gibberellins A₄ and A₇ - SD8339 6-benzyl-amino-9-(tetrahydropyran-2-yl)-9H-purine