bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of photosynthesis and transpiration in relation to mercury‐induced root damage in spruce seedlings
Authors: Godbold Douglas L. , Hüttermann Aloys 
Published: May 2006

Spruce seedlings [Picea abies (L.) Karst.] were exposed in nutrient solutions to a range of concentrations of HgCl2 and CH3HgCl for 7 weeks. The mineral, chlorophyll and water contents of the needles, and dry weights of root and needles were then estimated. The rates of photosynthesis, transpiration and dark respiration of the intact plants were determined using a Li‐cor portable photosynthesis‐measuring system. CO2 uptake decreased as the supply of both forms of Hg increased. Rates of transpiration were significantly reduced only after exposure to CH3HgCl. Similar concentrations of Hg were found in needles independent of the form of Hg supplied. Decreased rates of CO2 uptake at 100 nM HgCl2 and 1 nM CH3HgCl could be explained by lower levels of chlorophyll, and by lower levels of chlorophyll and closed stomata at all other CH3HgCl concentrations. Only at 1000 nM HgCl2 were other photosynthetic parameters affected.Decreased rates of transpiration and the lower chlorophyll levels in the needles did not appear to be due to the direct action of Hg, but rather to root damage that leads to a decrease in water supply and nutrient levels in the needles.
Diurnal export and carbon economy in an expanding source leaf of cucumber at contrasting source and sink temperature
Authors: Verkleij Frans N. , Challa Hugo 
Published: May 2006

Effects of contrasting temperatures of an expanding leaf (source) and of remaining plant parts (sink) on diurnal export and distribution of carbon were studied in seedlings of Cucumis sativus L., cv. Farbio. The time course of the rate of export was calculated by measuring simultaneously the exchange of 14CO2 and the amount of 14C in the source leaf by means of a Geiger‐Müller detector using a steady‐state labelling technique.In all treatments average export rate during the night (16 h) was maximally 50% of the average rate during the 8‐h day. Temperature affected the diurnal course of export via the source leaf and the sink in different ways. At a source leaf temperature of 25 or 30°C export stopped 12 h after start of the night, whereas at 20°C export continued throughout the night. However, the total amount of carbon exported during a 24 h cycle, expressed as a proportion of the amount of carbon assimilated, was the same at source leaf temperatures of 20 or 30°C. Thus source leaf temperature did not affect the distribution of assimilates between source and sink, in contrast to sink temperature. After 24 h at a sink temperature of 30°C, 20% more 14C was exported to plant parts below the source leaf than with a sink temperature of 20°C, at the expense of carbon remaining in the source.During the day less starch and more structural dry matter was formed at a source leaf temperature of 30°C than at 20°C. After a complete day/night cycle, however, there was no difference between the treatments. Starch was the primary carbon source during the night, and the decline in the rate of export coincided with the depletion of starch. Thus the decline in the rate of export at a source leaf temperature of 25 or 30°C at 12 h after the start of the night was due to the depletion of starch at that time. Similarly, at 20°C export could continue until the end of the night as the starch degradation supplied assimilates during the whole night.
The effects of illumination sequence, CO2 concentration, temperature and acclimation on the convexity of the photosynthetic light response curve
Authors: Leverenz Jerry W. 
Published: May 2006

It was shown previously that the convexity (curvature or rate of bending) of the photosynthetic light response curve was strongly correlated with chlorophyll content in shade acclimated conifer needles (Leverenz 1987, Physiol. Plant. 71: 20–29), in agreement with an hypothesis that gradients of light within leaves affect the convexity. In the present study it is shown that the convexity at any given chlorophyll content can be altered when leaves of Pinus sylvestris L. Picea glauca (Muench), Picea mariana (M.II.) BS.P. and Picea abies (L.) Karst pre‐treated with less shade. This probably induced a differential acclimation of cells on the top and bottom sides of the leaves to their local light environment. Leaves were illuminated on i) their top surface, ii) their bottom surface, or iii) uniformly in a light integrating sphere during measurements of photosynthesis. After shoots had been transferred from their growth environment to a new measuring environment, the convexity increased from the first to the second day towards a maximum of 0.97. The rate of increase towards this maximum was 55 to 62% per day and probably is the result of re‐acclimation of cells within the leaves. The data shown that the act of measuring photosynthesis induces a significant alteration in the experimental material when measurements are made for more than one day.The convexity of the light response curve of photosynthesis, was independent of whether the steady state measurements were made beginning in the dark and sequentially increasing photon flux density or beginning at high light and sequentially lowering photon flux density. Neither variation of CO2 concentration from 35 to 200 Pa, nor of temperature from 5° to 32°C affected the convexity.
A measurement system to detect small plant movements
Authors: Eidesmo T. , Johnsson A. 
Published: May 2006

A measurement system based on a photodiode array technique is presented, together with some results from recordings of phototropic responses of Avena sativa L. (cv. Seger I) coleoptiles.A commercial photodiode array (RL‐256G) was used, controlled by a likewise commercial control board RC‐301. Electronic circuits were built to connect the control board to the interface card IO‐801 of an Apple IIe microcomputer. The circuits constitute a fast temporary memory, which mainly contains two shift registers and two timers. Programs, which control the measurements, have been written and are presented.Detailed recordings of blue light induced phototropic movements are presented: resolution and other features of the equipment are discussed.
Apical dominance inPhaseolus vulgaris. The triggering effect of shoot decapitation and leaf excision on growth of the lateral buds
Authors: McIntyre Gordon , Damson Erich 
Published: May 2006

It was postulated that the release of lateral buds from apical dominance is triggered by the immediate increase in apoplastic water potential (hydrostatic pressure) that is produced by shoot decapitation and that is rapidly transmitted throughout the plant. In experiments conducted to test this hypothesis the use of a strain gauge transducer capable of measuring bud growth with an accuracy of ± 0.1 μm, showed that growth of the inhibited lateral bud at the primary leaf node ofPhaseolus vulgaris(L.) ev. Canadian Wonder was initiated within 1 to 5 s following shoot decapitation or excision of the primary leaves. When only the apical bud was excised the lateral bud showed a brief, transitory growth response of ca 1 min duration, but the axillary buds of the first and second trifoliate leaves were released from inhibition. Decapitation of the shoot just below the first trifoliate leaf induced a lateral bud response characterized by three distinct stages: a) a rapid initial growth response with a mean duration of 4.9 min b) a period of arrested growth, which varied in duration from 2 min to 4 h and c) the subsequent resumption of growth.Excision of both primary leaves induced a rapid but transitory bud response of considerably greater duration than that induced by apical bud excision. Excision of the primary leaves prior to decapitation of the shoot eliminated the phase of arrested growth, which characterized the bud response to decapitation of the intact plant. The rapidity of the bud response to both shoot decapitation and leaf excision and the interaction between the effect of these two treatments are consistent with the hypothesis that competition for water plays a major role in the correlative inhibition of lateral buds.
The uptake of phenylalanine into suspension‐cultured cells of Atropa belladonna
Authors: Nyman Seija , Simola Liisa Kaarina 
Published: May 2006

When suspension‐cultured cells of Atropa belladonna L. were in late growth phase, phenylalanine, one of the early precursors of atropine, was taken up mainly by diffusion without carrier but also actively via mediated transport. The uptake capacity of different callus lines varied from 0.4 to 1.9 μol (g fresh weight)−1 h−1 with an optimum pH at 4.5 or 5.0, depending on the callus line, 2,4‐Dinitrophenol (DNP) and KCN inhibited about 35–45% of the total uptake in all tested callus lines, so that a part of the uptke was dependent on metabolic energy.The rate of phenylalanine uptake was fastest from 2 to 7 days after the start of the suspension culture. The increase was from 50 to 300%, depending on the cell line. The enhancement was mainly due to increased mediated uptake and could be inhibited by cycloheximide during the first days of the suspension culture. Glutamine, added to the nutrient medium, also prevented the increase. The inhibition caused by glutamine together with cycloheximide was not additive. Obviously, glutamine did not directly affect the carrier, but possibly repressed its synthesis. When cells entered the stationary phase, the total uptake began to decrease, and most of it was non‐mediated. The suspension cultures of A. belladonna had only limited capacity to regulate the transport of phenylalanine into the cells at this phase of growth.
Fusicoccin, an inhibitor of brassinosteroid‐induced ethylene production
Authors: Arteca Richard N. , Bachman Jeannette M. , Tsai De‐Sheng , Mandava N. Bushan 
Published: May 2006

Fusicoccin was evaluated for its effects on brassinosteroid (BR), indole‐3‐acetic acid (IAA) and BR + IAA‐induced ethylene, 1‐aminocyclopropane‐1‐carboxylic acid (ACC) and ACC‐synthase production by etiolated mung bean (Vigna radiata L. Rwilez cv. Berken) hypocotyl segments. Fusicoccin inhibition of ethylene and ACC production induced by 2 μM BR started at concentrations as low as 0.05 μM. Maximum inhibition occurred at a 1 μM concentration with no further inhibition at higher concentrations tested. Fusicoccin (1 μM) was effective in the inhibition of BR‐induced ethylene, ACC and ACC‐synthase production at low and high concentrations of BR.Fusicoccin at concentrations as high as 2 μM had no effect on ethylene and ACC production promoted by low concentrations of IAA (1 to 10 μM). When higher concentrations (100–1000 μM) of IAA were used, fusicoccin (1 μM) had an inhibitory effect on ethylene and ACC production. Interestingly, fusicoccin (1 μM) had little or no effect on ACC‐synthase promoted by high concentrations of IAA (1000 μM).When BR and IAA were used in combination, fusicoccin inhibited ethylene and ACC production at concentrations as low as 0.05 μM with maximum inhibition occurring at 0.5 μM. At a 1 μM concentration, fusicoccin was effective in inhibiting the synergistic stimulation of ACC‐synthase promoted by BR and IAA.
Effects of vesicular‐arbuscular mycorrhizal infection and phosphate on Plantago major ssp. pleiosperma in relation to the internal phosphate concentration
Authors: Bass Rob , Lambers Hans 
Published: May 2006

Two experiments were carried out to study physiological effects of vesicular‐arbuseular mycorrhizal infection on Plantago major L., ssp. pleiosperma (Pilger). In the first experiment, infection by the Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe increased growth, shoot to root ratio, P concentrations in both shoot and roots and total uptake of P per plant. The percentages of dry matter in both shoot and roots were lower in mycorrhizal plants.In the second experiment different P treatments were applied to both mycorrhizal and non‐mycorrhizal P. major plants to separate any effects of mycorrhizal infection from increased uptake of P. In addition to the effects found in the first experiment, mycorrhizal, P, and mycorrhizal x P interaction effects were found on root respiration rate and the concentration of soluble sugars in the roots. No clear effects on total dry weight, N and starch concentrations in shoot and roots and sugar concentraion in the shoot were found. Irrespective of the mycorrhizal treatment, increased P concentration in the shoot correlated with an increased shoot to root ratio and root respiration rate, and a decreased percentage dry matter and sugar concentration in the roots. However, the root respiration rate and the P concentration in the roots of mycorrhizal plants were enhanced more than expected from the increased P concentrations in the shoots of these plants.
Effects of hardening and freezing stress on membrane lipids and CO2 fixation of Ceratodon purpureus protonemata
Authors: Aro Eva‐Mari , Karunen Pirjo 
Published: May 2006

Membrane lipids and steady‐state CO2 fixation rates were studied in moss protonemata in order to evaluate separately the effects of growth temperature, freezing stress and the achievement of frost hardiness. Protonemata of Ceratodon purpureus (Hedw.) Brid, were grown at 20 and 4°C and parts of both materials were then hardened. The low growth temperature increased the content and unsaturation level of membrane lipids significantly. This did not, however, cause a noticeable increase in the frost hardiness. Nor was the achievement of frost hardiness in this material accompanied by further changes in the amount or unsaturtion level of any membrane lipid class. Cytoplasmic membranes were abundant in both unhardened and hardened materials grown at 4°C, which agreed with the high phospholipid content of these protonemata. The only significant difference in membrane lipids between unhardened and hardened materials was a 50% lower level of trans 16:1 fatty acid in the phosphatidylglycerol fraction of hardened protonemata.In hardened protonemata monogalactosyldiacylglycerol (MGDG) was the membrane lipid most liable to decrease during the freeze‐thaw cycle. The loss of MGDG was accompanied by partial inhibition of CO2 fixation. Provided the content of phospholipids remained unchanged (freeze‐thaw cycle with – 10°C in hardened protonemata), this inhibition was mostly reversible. If loss of the phospholipids also had occurred during the freeze‐thaw cycle, as was the case in unhardened material at or below ‐10°C, CO2 fixation was severely and nearly irreversibly inhibited after thawing.
Leaf senescence in Festuca pratensis: accumulation of lipofuscinlike compounds
Authors: Düggelin Theres , Bortlik Karlheinz , Gut Hans , Matile Philippe , Thomas Howard 
Published: May 2006

Fluorescent compounds (FCs) with spectral properties comparable to those of lipofuscin‐like compounds are present in aqueous methanolic extracts of senescent meadow fescue, Festuca pratensis Huds., leaves. An HPLC system for the separation of FC from other fluorescent materials was developed. The chromatograms suggest that the FC‐fraction consists of a large number of chemically related compounds. FCs are accumulated during senescence in leaves of a yellowing genotype, cv. Rossa. In leaves of a non‐yellowing genotype, Bf 993, only traces of FCs appear at advanced stages of senescence.FCs are regarded as final products of lipid peroxidation. Since both yellowing and non‐yellowing genotypes are competent with regard to the degradation of galactolipids (the potential sources of polyunsaturated fatty acids) as well as regarding lipoxygenase (EC 1.13.11.12; a key enzyme of lipid peroxidation), and since incompentence to degrade chlorophyll is associated with lack of FC accumulation in the mutant genotype, it is hypothesized that the polar FCs present in senescent F. pratensis leaves represent catabolites of chlorophyll.
Can a limitation in pholem supply to nodules account for the inhibitory effect of nitrate on nitrogenase activity in soybean?
Authors: Vessey J. Kevin , Walsh Kerry B. , Layzell David B. 
Published: May 2006

Within 48 h of exposure of nodulated soybean [Glycine max (L.) Merr. cv. Harosoy 63 x Bradyrhizobium japonicum USDA 16] to 10 mM NO3, significant decreases were observed in nodule‐specific nitrogenase (EC 1.7.99.2) activity and CO2 evolution and in the proportion of [14C]‐labeled photosynthate partitioned to nodule biomass and respiration. These trends continued over the subsequent 3 days of the study period. Concomitant with these events was an 137% increase in the relative growth rate of the whole plant and a cessation in nodule growth. Although the concentration of total soluble sugar in nodules was not affected by NO3 treatment, the concentration of starch declined to 13% of the control level after 2 days exposure to NO3−. In contrast to the effects of NO3−, nodules in which nitrogenase activity was partially inhibited by a 30 min exposure to 100% O2, showed a 52% increase over control in the starch pool over a 72 h period.The results were compared with recent studies of NO3− inhibition of nitrogenase activity in legumes, and in contrast to these studies it was concluded that the inhibitory effects of NO3− could be accounted for by alterations in photosynthate partitioning to nodules. A hypothesis is proposed which attempts to account for the recent observation (J. K. Vessey, K. B. Walsh, and D. B. Layzell 1988. Physiol. Plant. 73: 113–121) that nitrogenase activity in phloem‐limited and nitrate‐inhibited nodules is limited by O2 diffusion. This hypothesis separates the concepts of photosynthate partitioning and phloem supply from that of carbohydrate deprivation and related effects on the size of the carbohydrate pools in nodules.
Circular dichroism of phytochrome intermediates
Authors: Eilfeld Petra H. , Eilfeld Peter G. 
Published: May 2006

Phototransformation Ptto Pfrwas investigated with 124‐kDa phytochrome from etiolated oat seedlings (Avena sativaL. cv. Pirol) using circular dichroism spectroscopy at ‐110°C to +30°C. Using absorption spectra of the intermediates formed at the respective temperatures, circular dichroism spectra (300–800 nm) of pure intermediates were calculated.The sign of the circular dichroic absorption bands changed upon formation of lumi‐R, the primary photoproduct of Pr. This would be compatible with a Z→E isomerization taking place at this reaction step. The subsequent intermediates (meta‐Raand meta‐Rc) as well as Pfrshowed only small circular dichroism. Their absorption spectra were drastically shifted, but had similar spectral shapes. The results are discussed in terms of conformational changes of the phytochrome chromophore presumably taking place at the early steps of phototransformation Prto Pfr.
Partial characterization of a major family of proteins in turions of Hydrilla verticillata
Authors: Ryan Frederick J. 
Published: May 2006

Electrophoretograms of turions of dioecious Hydrilla verticillata (L. f.) Royle, run under non‐denaturing conditions, had a major complex protein band at Rf0.45 (7.5% acrylamide). Extracts of monoecious plants under similar conditions had major bands at Rf 0.43 and 0.45. The polypeptides which comprise these bands were partially purified and characterized. The major protein fraction in extracts of dioecious turions had a molecular mass of 58 kDa on gel permeation chromatography. Electrophoresis of this fraction under denaturing conditions in the presence of sodium dodecyl sulfate indicated principal bands with molecular masses of 58 and 57 kDa. Extracts from turions of the monoecious biotype had major bands at 59 and 55 kDa after electrophoresis under denaturing conditions.Antisera were raised against the proteins from the dioecious turion at Rf 0.45 after electrophoresis under non‐denaturing conditions. When blots of gels run under non‐denaturing conditions were probed with these antisera, a complex band was seen at Rf 0.45 for extracts of the dioecious biotype, while bands were observed at Rf 0.43 and 0.45 for the monoecious extracts. After electrophoresis under denaturing conditions, immunoreactive bands were noted at 58 and 57 kDa or 59 and 55 kDa in extracts of dioecious and monoecious turions, respectively.Extracts of leaves and stems of H. verticillata had detectable amounts of immunoreactive proteins, regardless of photoperiod, hence turion production. Related plants with the aquatic habit had immunoreactive proteins in their leaves and organs of perennation [Elodea canadensis Michx., Elodea nuttallii (Planch.) St. John, and Egeria densa Planch., Potamogeton nodosus Poir. and P. pectinatus L.], but the presence of these proteins was not noted in other plants (Zea mays L., Allium cepa L., Spinacia oleracea L., Lemna gibba L., or Solanum tuberosum L.).
Effect of tentoxin on K+transport in winter wheat seedlings of different K+‐status
Authors: Klotz Martin G. , Erdei László 
Published: May 2006

Klotz, M. G. and Erdei, L. 1988. Effect of tentoxin on K+ transport in winter wheat seedlings of different K+‐status.The influence of the phytoeffective mycotoxin, tentoxin, [cyclo‐(L‐leucyl‐N‐methyltrans‐dehydronhenyl‐alanyl‐glycyl‐N‐methyl‐L‐alanyl)] (in K+ uptake and on translocation of K+ from roots to shoot was studied in 14‐day‐old winter wheat plants (Triticum aestivum L. cv. Martonvásári‐8) grown at different levels of K+ supply. For comparison, the effects of 2,4‐dinilrophcnol and valinomycin were also investigated. In I‐h experiments I pM tentoxin reduced K+ influx in the routs over the external K+ concentration range 0.1 to 1 mM (low‐K+ plants), whereas stimulation was observed al lower and higher K+ concentrations. On the other hand, in plants grown at 0.3 mM K+, tentoxin stimulated the translocation of K+ from roots to shoots in 5‐h experiments. Valinomycin affected K+ transport only al high K+‐status (slight stimulation). In low‐K+ plants 2,4‐dinitrophenol (DNP) caused drastic inhibition of K+ uptake, but in high‐K+ plants uptake was only slightly inhibited and translocation slightly stimulated, It is concluded that the opposite effects of tentoxin on K+ uptake and translocation agree1 with the directions of the H+‐ATPases pumping H+ towards the apoplast and located at the cortex plasmalemma and the xylem parenchyma plasma‐membrane, respectively. These effects should probably be attributed to the interaction between tentoxin and the K+‐carrier protein rather than to a direct influence of tentoxin on H+‐ATPase.