bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization and localization of three soluble invertase forms from Lilium longiflorum flower buds
Authors: Miller William B. , Ranwala Anil P.
Published: May 2006

Three invertase forms (EC 3.2.1.26) were identified in soluble extracts from developing flower buds of Lilium longiflorum Thunb. cv. Nellie White. The enzymes were separable on a diethylaminoethyl (DEAE)‐Sephacel column and designated invertase I. II or III according to the order of elution from Sephacel. To determine tissue specificity of these floral invertases, anthers were separated from tepal. pistil and filament tissue, and analyzed for invertase activity. Invertase I was localized primarily in anthers, with invertases II and III being present in much smaller amounts (less than 5% of the invertase I activity). Much higher levels of invertases II and III were found in the nonanther organs of the flower, where essentially no invertase 1 was detectable. Further purification of each form (using gel filtration. Con‐A‐Sepharose affinity chromatog‐raphy and hydrophobic interaction chromatography on phenyl‐agarose) resulted in 135‐ 189‐ and 202‐fold purification of pooled fractions from DEAE‐Sephacel. respectively, and established that each invertase form is a glycoprotein. Each was an acid invertase. with pH optima between 4.0 and 5.0 and an apparent molecular mass of 77 500 Da (as determined by Sephadex gel filtration). The invertases had sucrose Km values of 1.0. 6.4 and 6.6 mM. and temperature optima of 40. 50 and 45°C. respectively. A temperature stability study revealed that invertase III was the most thermostable, followed by II and I. Invertases II and III had lower affinity to raffinose and stachyose than invertase I. All three enzymes were completely inhibited by Hg2+ or Ag+ ions at 1.7 mM. At this concentration. Cu2‐showed differential partial inhibition. Although fructan was shown to be present in both anther and nonanther tissues of Lilium flower buds, these invertases showed no sucrose:sucrose fructosyltransferase (EC 2.4.1.99) activity.
The effect of light quality on the induction of efficient photosynthesis under low CO2 conditions in Chlamydomonas reinhardtii and Chlorella pyrenoidosa
Authors: Borodin Valery , Gardeström Per , Samuelsson Göran
Published: May 2006

The effect of blue and red light on the adaptation to low CO2 conditions was studied in high‐CO2 grown cultures of Chlorella Pyrenoidosa (82T) and Chlamydomonas reinhardtii(137+) by measuring O2 exchange under various inorganic carbon (Ci) concentrations. At equal photosynthetic photon flux density (PPFD), blue light was more favourable for adaptation in both species, compared to red light. The difference in photosynthetic oxygen evolution between cells adapted to low Ciunder blue and red light was more pronounced when oxygen evolution was measured under low Ci compared to high Ci conditions. The effect of light quality on adaptation remained for several hours. The different effects caused by blue and red light was observed in C. pyrenoidosa over a wide range of PPFD with increasing differences at increasing PPFD. The maximal difference was obtained at a PPFD above 1 500 μmol m−2s−1. We found no difference in the extracellular carbonic anhydrase activity between blue‐ and red light adapted cells.

The light quality effect recorded under Ci‐limiting conditions in C. reinhardtii cells adapted to air, was only 37% less when instead of pure blue light red light containing 12.5% of blue light (similar PPFD as blue light) was used during adaptation to low carbon. This indicates that in addition to affecting photosynthesis, blue light affected a sensory system involved in algal adaptation to low Ci conditions. Since the affinity for Ci of C. Pyrenoidosa and C. reinhardtii cells adapted to air under blue light was higher than that of cells adapted under red light, we suggest that induction of some component(s) of the Ci accumulating mechanism is regulated by the light quality.
Is cytoplasmic pH involved in the regulation of cell cycle in plants?
Authors: Pichon Olivier , Desbiez Marie‐Odile
Published: May 2006

Modifications of cytoplasmic pH has biological significance in animal and plant cell development. Many observations suggest an important function of cytopiasmic pH in mitotic signalling in animal ceils. In Bidens pilosa cultivated under white light, acidification of cytoplasm, observed after mechanical trauma, is associated with an inhibition of DNA synthesis and a decrease in mitotic frequency. In contrast, in Bidens pilosa cultivated under blue light, mechanical stimulation induces an increase of cytoplasmic pH and stimulation of DNA duplication and mitotic activity. A correlation has been established between transient variations of cytoplasmic pH and rapid modification in cell development. The critical role of cytoplasmic pH in the regulation of the cell cycle in plants is discussed.
High yields in advanced lines of Pima cotton are associated with higher stomatal conductance, reduced leaf area and lower leaf temperature
Authors: Lu Zhenmin , Radin John W. , Turcotte Edgar L. , Percy Richard , Zeiger Eduardo
Published: May 2006

Advanced lines of Pima cotton (Gossypium barbadense L.) bred for higher yield potential and heat resistance have higher stomata conductance and smaller leaf areas than those of obsolete lines. In controlled experiments, five commercial lines of Pima cotton having increasing lint yield and heat resistance showed a gradient of increasing stomatal conductance and decreasing leaf size. In field experiments, heat‐sensitive, low yield Pima lines showed a lower stomatal conductance than high yielding, advanced lines. This indicates that selection for high yield potential and heat resistance has imposed a selection pressure for higher stomatal conductance and smaller leaf areas. The higher stomatal conductance and smaller leaf area in the advanced lines resulted in a lower leaf temperature in both controlled environments and in the field. The largest leaf temperature differences between obsolete and advanced lines were observed in the afternoon. These differences coincided with the largest differences in stomatal conductance and the highest air temperatures. Measurements of stomatal conductance and leaf temperature in field‐grown progeny from a cross between the advanced line, Pima S‐6. and the obsolete line, Pima 32, showed that genetically determined differences in stomatal conductance resulted in corresponding differences in leaf temperature. None of the altered physiological traits were selected for in the breeding program, indicating that selection for the desired agronomic traits imposed selection pressures on the altered physiological traits. The increases in stomatal conductance and decreases in leaf area could represent an integrated response to selection pressures on enhanced evaporative cooling, ensuing from selection for heat resistance.
Selection for higher yields and heat resistance in Pima cotton has caused genetically determined changes in stomatal conductances
Authors: Lu Zhenmin , Zeiger Eduardo
Published: May 2006

Gas exchange analysis was used to characterize photosynthetic and stomatal responses to key environmental stimuli in five commercial lines of Pima cotton (Gossypium barbadense L.) which represent a gradient of selection for higher yields and heat resistance, and a primitive, uncultivated G. barbadense. At constant light and vapor pressure deficit, stomatal conductance increased linearly with air temperature in the 23 to 36$C range in all five commercial lines, and conductance at each temperature increased as a function of selection. In contrast, photosynthetic rates had a low sensitivity to temperature in the 23 to 36$C range, particularly in the advanced lines. In a segregating F2 population from a cross between the advanced line, Pima S‐6, and the primitive cotton, B368, the slope of the stomatal response to temperature in each F2 plant was positively correlated with the stomatal conductance measured at 40$C. An analysis of the frequency distribution of stomatal conductance in F1 and F2 progeny of the cross showed that the differences in stomatal conductance between lines were genetically determined. These data indicate that selection for higher yield and heat resistance in Pima cotton has caused genetically determined changes in stomatal properties. Characterization of the relationship between the altered stomatal properties and the attained increases in heat resistance and yields could make it possible to use these physiological traits as selection criteria in future breeding programs.
Characterization of spinach leaf α‐l‐arabinofuranosidases and β‐galactosidases and their synergistic action on an endogenous arabinogalactan‐protein
Authors: Hirano Yasushi , Tsumuraya Yoichi , Hashimoto Yohichi
Published: May 2006

Two β‐galaclosidases (β‐Galase‐I and ‐II, EC 3.2.1.23) and two α‐l‐arabinofuranosidases (α‐l‐Arafase‐I and ‐II. EC 3.2.1.55). were purified from mesophyll tissues of spinach (Spinacia oleracea L.), using chromatography on DEAE‐cellulose, lactose‐conjugated Sepharose CL‐4B, and Sephadex G‐100, or on hydroxylapatite and Sephadex G‐150. The apparent molecular mass (Mr) of β‐Galase‐I and ‐II, respectively, were estimated to be 38 000 and 58 000 on SDS‐PAGE and 64 000 and 60 000 on gel‐permeation chromatography, indicating that the former was a dimeric protein. The isoelectric points of β‐Galase‐I and ‐II were 6.9 and 5.2, respectively. Both enzymes hydrolyzed maximally p‐nitrophenyl (PNP) β‐galactoside at pH 4.3, and were activated about 2‐fold in the presence of BSA (100 μg ml−1). The activity of both enzymes was inhibited strongly by heavy metal ions and p‐chloromercuriberszoate (p‐CMB). d‐Galactono‐(1→4)‐lactone and d‐galactal served as potent competitive inhibitors for the enzymes. β‐Galase‐I and ‐II could be distinguished from each other in their relative rates and kinetic properties in the hydrolysis of aryl β‐galactosides as well as of lactose and galacto‐oligosaccharides. In particular. β‐Galase‐I exhibited a preferential exowise cleavage of β‐1,6‐galactotriose and β‐1.3‐galactan. α‐l‐Arafase‐l (Mr 118000) and ‐II (M, 68 000) were optimally active on PNP α‐l‐arabinofuranoside at pH 4.8 and gave Km values of 1.2 and 2.2 mM. respectively. l‐Arabino‐(1 → 4)‐lactone. Ag+, and SDS acted as inhibitors for the isozymes. α‐lArafase‐I was characterized by its activity to hydrolyze PNP β‐d‐xylopyranoside besides PNP α‐l‐arabinofuranoside. inhibition by d‐xylose and d‐glucono‐(1 → 5)‐lactone. and less sensitivity to Hg2+. Cu2+, and p‐CMB. Sugar beet arabinan was hydrolyzed rapidly by α‐lArafase‐II at one‐half the rate for PNP α‐larabinofuranoside, while the polysaccharide was less susceptible to α‐lArafase‐I. A spinach leaf arabinogalactan‐protein was practically resistant to the action of β‐Galases, but its susceptibility to the enzymes increased remarkably after prior hydrolysis with α‐lArafase‐Il.
Assays for three enzymes involved in mevalonic acid metabolism
Authors: Sandmann Gerhard , Albrecht Manuela
Published: May 2006

Enzyme assays have been developed for mevalonate (MVA) kinase, mevalonate phosphate (MVAP) kinase and mevalonate pyrophosphate (MVAPP) anhydrodecar‐boxylase. The procedures involve radioactively labelled substrates and separation of the reaction products by anion exchange chromatography. The separation on Dowex 1‐X2 in self‐packed microcolumns is simple, inexpensive and results in good separation of the MVA derivatives from each other. Because separation of MVAPP from isopenteny] pyrophosphate (IPP) was not possible directly, samples or column fractions containing MVAPP and IPP simultaneously were dephosphorylated by alkaline phosphatase. The resulting MVA and isopentenol are then easily separated in the same system. The assays for all three enzymes not onlv allows the determination of activities in crude enzyme preparations but is also applicable to the in vitro determination of intermediate pools in the reaction sequence from MVA to IPP after using 14C‐MVA as substrate. The major advantage is accuracy and ease of use. The utility of the methods was demonstrated for enzyme extracts from the higher plants Chenopodium and spinach as well as for the fungus Phycomyces.
Differential response of nitrate reductase and sucrose‐phosphate synthase‐activation to inorganic and organic salts, in vitro and in situ
Authors: Huber Steven C. , Huber Joan L. , Kaiser Werner M.
Published: May 2006

Studies were conducted to compare the modulation of β‐nicotinamide adenine dinucleotide (NADH): nitrate reductase (NR; EC 1.6.6.1) and sucrose‐phosphate synthase (SPS: EC 2.4.1.14) with respect to regulation by the inorganic anions, phosphate (P1), sulfate and tungstate. Following inactivation of both enzymes in vivo by transferring spinach plants (Spinacia oleracea L. cv. Bloomsdale) to a darkened growth chamber, spontaneous reactivation occurred in vitro when desalted leaf extracts were preincubated at 25°C prior to assay. All three inorganic anions inhibited SPS activation in vitro and also reduced the light activation of SPS in situ when they were fed to excised leaves via the transpiration stream. As expected, feeding tungstate to excised leaves prevented the light‐dependent increase in extractable NR activity. However, in contrast to SPS, the light activation of NR in situ was relatively unaffected by Pi, and sulfate, and in vitro, both anions stimulated (rather than inhibited) the reactivation of NR. Part of the stimulation by Pi and sulfate was the result of increased ionic strength, and stimulation could also be demonstrated with other inorganic and organic salts. In the presence of high ionic strength (0.1 to 0.2 M KCl) the rate of NR activation in vitro was relatively constant when the pH of the preincubation medium was varied from pH 6.5 to 8.0, whereas in the absence of added salt the rate of activation was nearly zero at pH 6.5 but increased progressively as pH was raised. The stimulation by salts could be reversed, in part, by glycerol and ethylene glycol suggesting that hydrophobic interactions might play some role in the activation of NR.
Pyrophosphate:fructose‐6‐phosphate 1‐phosphotransferase from barley seedlings. Isolation, subunit composition and kinetic Characterization
Authors: Nielsen Tom Hamborg
Published: May 2006

Pyrophosphate:fructose‐6‐phosphate I‐phosphotransferase (PFP: EC 2.7.1.90) was purified 260‐fold from leaves of etiolated barley seedlings. The purified enzyme consisted of two subunits, with apparent molecular masses of 65 (α) and 60 (β) kDa. Polyclonal antibodies were raised against the denatured PFP protein eluted from an SDS‐polyacrylamide gel. The antibodies recognized both denatured and native PFP. Western blots of crude extracts showed that the activity of PFP in barley leaves is correlated to the amount of PFP protein, and that both the α‐ and the β‐subunits are present in near stoichiometric amounts in all investigated tissues. The apparent molecular mass of the boloenzyme. as determined by gel filtration chromatography, was dependent on the presence of pyrophosphate. In absence of pyrophosphate. barley PFP elutes as a heterotetramer whereas it elutes as a heterooctamer in the presence of 20 mM pyrophosphate. Pure PFP obtained by gel filtration chromatography in the presence of 20 mM pyropnosphaie reached a specific activity of 28 U mg−1. Barley PFP was characterized with respect 10 kinetic properties in the forward direction (use of PP1) and in the reverse direction (formation of PP1). The affinity for the activator Fru‐2.6‐P2: was very high, with an estimated K3 of 2.8 nM when PFP activity was assayed in the forward direction.
Differences in sucrose metabolism relative to accumulation of bird‐deterrent sucrose levels in fruits of wild and domestic Vaccinium species
Authors: Darnell Rebecca L. , Cano‐Medrano Raquel , Koch Karen E. , Avery Michael L.
Published: May 2006

We examined variability in sucrose levels and metabolism in ripe fruits of wild and domestic Vaccinium species and in developing fruits of cultivated blueberry (V. ashei and V. corymbosum). The objective was to determine if sufficient variability for fruit sucrose accumulation was present in existing populations to warrant attempts to breed for high‐sucrose fruit, which potentially would be less subject to bird predation. Threefold differences in fruit sucrose concentration were found among Vaccinium species, ranging from 19 to 24 mg (g fresh weight)−1 in V. stamineum and V. arboreum to approximately 7 mg (g fresh weight)−1 in cultivated blueberry (V. ashei and V. corymbosum) and V. darrowi. Hexose levels were similar among species, ranging from 90 to 110 mg (g fresh weight)–1, and glucose and fructose were present in equal amounts. Soluble acid invertase (EC 3.2.1.26) activity was negatively correlated with fruit sucrose concentration. There was no apparent correlation between fruit sugar concentration and either sucrose synthase (EC 2.4.1.13) or sucrose phosphate synthase (EC 2.4.1.14) activities, both of which were low for all species studied. Developmental increases in fruit sugar levels of cultivated blueberry followed a pattern similar to that observed in fruit fresh weight accumulation. Hexose concentrations ranged from 6 to 30 mg (g fresh weight)−1 during the first 60 days after anthesis. Between 60 days and fruit ripening (80 days), hexose levels rose from 30 to 80 mg (g fresh weight)−1. Sucrose was not detected in fruits until ripening, when low levels were found. Insoluble acid invertase activity was relatively high early in fruit development, decreasing as soluble acid invertase activity increased. Between 60 days and fruit ripening, soluble acid invertase activity increased from 3 to 55 μmol (g fresh weight)–1 h–1. Both sucrose synthase and sucrose phosphate synthase activities were low throughout development. The extent of sucrose accumulation in fruits and the degree of variability for this trait among Vaccinium species support the feasibility of developing high sucrose fruits, which would be a potentially valuable addition to current strategies of minimizing crop losses to birds.
Effects of growing conditions and development of the underlying exodermis on the vitality of the onion root epidermis
Authors: Barrowclough David E. , Peterson Carol A.
Published: May 2006

Bulbs of Allium cepa L., which had developed short, adventitious roots, were transferred to various conditions, i.e. vermiculite watered to saturation, vermiculite watered to half saturation, immersed in hydroculture, and immersed in hydroculture except for the proximal 20 mm which was continuously exposed to air. The development of the exodermis occurred in a patchy fashion in many roots but was not influenced by the growing conditions. The vitality of the epidermis declined under all conditions, the rate of decline being inversely related to the ambient moisture level. The differences between the treatments were most evident at the oldest region sampled (120 mm from the root tip) where 4% of the epidermal cells were dead in roots grown in hydroponics. This compared with 62% dead cells in saturated vermiculite, 78% in half‐saturated vermiculite and 92% in roots exposed to air. Death of the epidermal cells was not accelerated by the maturation of the underlying exodermis. Epidermal cells which did not overlie a short cell of the exodermis (i.e. were only in contact with long cells) died earlier than the others: this trend was evident even prior to the maturation of the exodermis. These results suggest that the epidermal cells are not well connected symplasmically to the long cells or to the neighbouring epidermal cells. The large majority of epidermal cells (98% of the total) were in contact with a short cell of the exodermis. These epidermal cells tended to die off slowly, even under very favourable ambient conditions. Since these cells provide the major site for ion uptake in roots with a mature exodermis. their death may reduce the efficiency of the root for this activity.
Light‐induced increase in the contents of ferulic and diferulic acids in cell walls of Avena coleoptiles: its relationship to growth inhibition by light
Authors: Miyamoto Kensuke , Ueda Junichi , Takeda Satomi , Ida Kazuko , Hoson Takayuki , Masuda Yoshio , Kamisaka Seiichiro
Published: May 2006

White fluorescent light (5 W m−2) inhibited Avena coleoptile growth. Light caused in increase in minimum stress relaxation time and a decrease in extensibility (strain/load) of coleoptile cell walls. Light increased the contents of ferulic acid (FA) and diferulic acid (DFA) ester‐linked to the hemicellulose I in cell walls. These changes in the phenolic contents correlated with those of the mechanical properties of cell walls, suggesting that light stimulates the formation of DFA in hemicellulose I, making cell walls rigid, and thus results in growth inhibition. The ratio of DFA to FA was almost constant in the dark, but decreased in light, although it was almost constant in Oryza coleoptiles either in the dark or in light (Tan et al. 1992). From this fact, it is speculated that in the light condition, the formation of DFA in cell walls is limited in the step of the peroxidase catalyzed coupling reaction to produce DFA, while in the dark it is limited in the step of the feruloylation of hemicellulose I.
Anatomical anomalies in crop formation plants
Authors: Levengood W. C.
Published: May 2006

Crop formations consist of geometrically organized regions ranging from 2 to 80 m diameter, in which the plants (primarily grain crops) are flattened in a horizontal position. Plants from crop formations display anatomical alterations which cannot be accounted for by assuming the formations are hoaxes. Near the soil surface the curved stems often form complex swirls with ‘vortex’ type patterns. In the present paper, evidence is presented which indicates that structural and cellular alterations take place in plants exposed within the confines of the ‘circle’ type formations, differences which were determined to be statistically significant when compared with control plants taken outside the formations. These transformations were manifested at the macroscopic‐level as abnormal nodal swelling, gross malformations during embryogenesis. and charred epidermal tissue. Significant changes in seed germination and development were found, and at the microscopic level differences were observed in cell wall pit structures. Affected plants also have characteristics suggesting the involvement of transient high temperatures.
Heavy metal binding by mycorrhizal fungi
Authors: Galli Ulrich , Schüepp Hannes , Brunold Christian
Published: May 2006

Ecto‐ and endomycorrhizal symbiosis can play a crucial role in protecting plant roots from heavy metals (HMs). The efficiency of protection, however, differs between distinct isolates of mycorrhizal fungi and different HMs. Fungal ecotypes from HM‐contaminated sites seem to be more tolerant to HMs than reference strains from non‐contaminated sites. The abundance of the extramatrical mycelium was shown to he important for HM binding by the fungus. Most of the HMs were demonstrated to be bound to cell wall components like chitin, cellulose. cellulose derivatives and mela‐nins. The chemical nature of HM‐binding substances in the fungal cells is not clear. Polyphosphate granules, which were proposed to have this function, seem to be artifacts of specimen preparation. The high N and S concentrations associated with the polyphosphate granules rather indicate the occurrence of HM‐thiolate hinding by metallothionein‐like peptides.
Starch metabolism in poplar wood ray cells during spring mobilization and summer deposition
Authors: Witt Wolfgang , Sauter Jörg J.
Published: May 2006

Seasonal variations of starch and soluble carbohydrates as well as extractable activities of enzymes involved in starch and maltose metabolism from 4‐year‐old twigs wood ofPopulus×CanadensisMoench ‘robusta’ were analysed during late winter, spring, and summer. A rapid decline of all enzymes occurred before or shortly after bud break in spring, accompanied by the complete degradation of starch and maltose. The inactivation proceded in a highly ordered sequence. Starch‐ and maltose‐synthesizing enzymes. March phosphorylase (EC 2.4.1.1), and D‐enzyme, (EC 2.4. 125) declined before hydrolysis of carbohydrates, while certain electrophoretic isoforms of amylases and maltose‐degrading enzymes persisted until the storage compounds were digested. The enzymes of starch synthesis, ADP glucose pyrophosphorylase (EC 2.7.7.27) and starch synthase (EC 2.4.1.21). increased already in late spring while the activity of all other enzymes stayed on a very low level during summer. Comparison of enzyme activities and rate of renewed starch deposition in June showed that both steps, catalysed by ADP glucose pyrophosphorylase and starch synthase. may be rate limiting.
Responses of seed of Stylosanthes humilis to germination regulators
Authors: Vieira Henrique D. , Barros Raimundo S.
Published: May 2006

Seed of Stlosanthes humilis both have hard integuments and display physiological dormancy, the latter being lost during post‐harvest ageing. Ethrel and l‐aminocyclopropane‐1‐carboxylic acid (ACC) partially released scarified young seed from physiological dormancy. Cobalt and silver ions and abscisic acid inhibited germination of scarified non‐dormant seed. Abscisic acid also inhibited germination of voung seed promoted by ACC. Thiourea and ethrel plus benzyladenine showed the greatest efficacy in breaking seed dormancy.
Transformation of Brassica napus by using the aadA gene as selectable marker and inheritance studies of the marker genes
Authors: Schröder Mia , Dixelius Christina , Råhlén Lennart , Glimelius Kristina
Published: May 2006

An Agrobacterium tumefaciens‐mediated transformation system for Brassica napus has been improved. We investigated several marker genes for transformation of Brassica napus, and the aadA gene, which confers resistance to streptomycin and spectinomycin, was found to be the most suitable. Forty‐three out of 193 putative transformants in the T1 generation were investigated by Southern blot analysis. Transformants containing a range of 1 to 10 integrated T‐DNA copies per genome were found. Total DNA from 35 plants showed hybridisation to both the aadA and the nptll marker gene probes, from 5 plants only to one marker gene probe and from 3 plants DNA did not hybridise to any of the gene probes. Furthermore, more complex integration patterns such as direct repeated copies of the T‐DNA, both as tandem and inverted copies, were observed. Inheritance of the marker genes in the T2 generation was studied in 37 of the plants. This revealed that 22% of the plants that contained both marker genes, segregated as one single locus (3:1) for both genes, while 46% of the plants gave a segregation pattern corresponding to one T‐DNA locus for at least one of the marker genes. Moreover, these inheritance patterns appeared to be more or less independent of the number of genes seen in the Southern blot analysis of the T, generation. In this study we show that the introduced marker genes are inherited by the T; generation in a less predictable way than was earlier reported for B. napus.
Gibberellic acid decreases anthocyanin accumulation in wild carrot cell suspension cultures but does not alter 3′‐nucleotidase activity
Authors: Ilan Avihai , Zanewich Karen P. , Rood Stewart B. , Dougall Donald K.
Published: May 2006

Gibberellic acid (GA3) applied at different times during the growth of wild carrot (Daucus carota ssp. Carota) cell suspension cultures inhibited anthocyanin accumulation. Application of 3 × 10–6M GA3 to cultures on day 0 or day 4 gave, respectively, 10 or 35% of anthocyanin accumulation relative to levels occurring when GA3 was applied at the end of the growth period. Endogenous GAs were separated by high pressure liquid chromatography, and identified and quantified by gas chromatography‐selected ion monitoring. Gibberellins GA1, GA3 and traces of GA8. GA19 and GA20 were identified in carrot cell suspension cultures of both high and low anthocyanin‐accumulating clones. The concentrations of GA1. GA3 and GA8 in the two clones were similar and were not significantly different after the application of uniconazole which promoted anthocyanin accumulation. This suggests that these endogenous GAs are not the sole factors controlling the accumulation of anthocyanin in these different clones. Exogenous GA3 and uniconazole had no effect on 3′‐nucleotidase and 5′‐nucleotidase activity in the carrot cell suspension cultures. Thus 3′‐nucleotidase does not appear to play a role in the inhibition of anthocyanin accumulation by exogenous GA3.
Changes in the levels of abscisic acid and its glucose ester conjugate during maturation of hybrid larch (Larix × leptoeuropaea) somatic embryos, in relation to germination and plantlet recovery
Authors: Lelu Marie‐Anne , Label Philippe
Published: May 2006

Changes in abscisic acid content during maturation of hybrid larch somatic embryos (Larix × leptoeuropaea), were followed using an enzyme immunoassay (ELISA). In the presence of 60 μM cis‐trans (±)‐ABA in the maturation medium, the cis‐trans (±)‐ABA level of the somatic embryos in planta increased during the maturation phase to reach a maximum value at week 5. Concomitantly, an extension of the period of maturation from 3 to 4 and 5 weeks resulted in a significant decrease in both germination and plantlet frequencies. As a consequence, we assume that it was the level of ABA in planta that was responsible for the inhibition. ABA acted in both a stimulatory and an inhibitory manner. If ABA promoted the obtention of high quality somatic embryos in large numbers, it also had a deleterious effect on the subsequent development, i.e. germination and plantlet recovery. The results stressed the importance of both the procedure and duration of maturation.
Differential expression of a chlorophyll a/b binding protein gene and a proline rich protein gene in juvenile and mature phase English ivy (Hedera helix)
Authors: Woo Ho‐Hyung , Hackett Wesley P. , Das Anath
Published: May 2006

Two cDNA clones representing mRNAs which are differentially expressed during in vitro culture of juvenile and mature leaf petioles of English ivy (Hedera helix L.) were isolated by differential screening. The mRNA represented by clone HW101 is expressed at a higher level in untreated juvenile than in untreated mature in‐vitro‐cultured petioles. Treatment of petioles with α‐naphthaleneacetic acid (NAA) at the initiation of culture decreases HW101 mRNA levels in juvenile but not mature, petioles. In intact plants. HW101 mRNA is expressed at a higher level in juvenile laminae, petioles and stems than in identical tissues of mature plants. DNA sequence analysis indicates that HW1O1 cDNA is significantly similar to a light harvesting chlorophyll a/b binding protein gene (Lhcb) of pea. The gene represented by the second clone. HW103, is expressed at a higher level in mature than in juvenile in‐vitro‐cultured petisoles. Treatment of petioles with NAA at the initiation of culture decreases HW103 mRNA levels in chronologically young mature but not older mature and juvenile petioles. However, expression of the HW103 gene is not detectable in petioles, or in any other vegetative organ tested, immediately after excision. It is, however, expressed in developing seeds. In otherwise intact plants, the HW103 gene is expressed in wounded petioles of mature plants 5 days after wounding but not in wounded petioles of juvenile plants. It is also expressed at a higher level in wounded stems of mature plants than in those of juvenile plants. However, it is not expressed in wounded lamina of either juvenile or mature plants. DNA sequence analysis indicates that HW103 cDNA is similar to a cell wall proline rich protein (PRP) gene of soybean. This is the first report of differential expression of a PRP gene in tissues from juvenile and mature plants. Southern blot analysis of nuclear DNA of H. helix shows that both HW101 and HW103 are members of small gene families.
Substitution of hydrazones for the 4′ carbonyl on abscisic acid rendered it ineffective in a rapid stomatal–opening–inhibition bioassay
Authors: Hite Daniel R. C. , Outlaw William H. , Seavy Margaret A.
Published: May 2006

A rapid stomatal bioassay to test abscisic acid (ABA)–like inhibition of stomatal opening was elaborated. The assay was sensitive to low concentrations of ABA (>50% inhibition of opening at 0.02 μM (+)‐S‐ABA) and was insensitive to 20 μM (+)‐S‐ABA‐1 ‐(methyl ester), which is consistent with previous work, With the original intent of developing anti‐idiotypic antibodies, we made conjugates of ABA at the 4′carbonyl because of its accessibility and known requirements for other positions of the ABA molecule in siomatal signal transduction. We found that these conjugates lacked ABA‐like activity and did not interfere with (+)‐S‐ABA in the stomatal bioassay, implying the importance of the 4′carbonyl. These observations cast doubt on the feasibility of using anti‐idiolypic antibodies produced through the use of 4′‐substituted ABA for the isolation of a guard‐cell ABA receptor.
Endogenous hormone levels during direct somatic embryogenesis in Medicago falcata
Authors: Ivanova Aneta , Velcheva Margarita , Denchev Plamen , Atanassov Atanas , Van Onckelen Henri A.
Published: May 2006

Endogenous indole‐3‐acetic acid, abscisic acid and cytokinins (zeatin, zeatin riboside, N‐isopentenyladenine and N‐isopentenyladenosine) were evaluated in initial explants (leaves) of in vitro propagated plants of alfalfa (Medicago falcata L.) lines varying in embryogenic capacity and during the somatic embryogenesis process. Fast embryo‐genic induction was correlated with high IAA and low ABA levels in the initial explants. No significant differences were observed in the cytokinin contents. Our results suggest that a certain hormone balance is necessary to allow the expression of the embryogenic potential. The consistent stages of the direct somatic embryogenesis are also characterized by changes in hormonal levels.
Ethylene synthesis and growth in embryogenic tissue of Norway spruce: Effects of oxygen, 1‐aminocyclopropane‐1‐carboxylic acid, benzyladenine and 2,4‐dichlorophenoxyacetic acid
Authors: Kvaalen H.
Published: May 2006

Ethylene production from an embryogenic culture of Norway spruce (Picea abies L.) was generally low. ca 2.5 nl g−1 h−1, whereas 1‐aminocyclopropane‐1 ‐carboxylic acid (ACC) concentration was high, fluctuating between 50 and 500 nmol g−1 during the 11‐day incubation period. Hypoxia (2.5 and 5 kPa O2) rapidly inhibited ethylene production without subsequent accumulation of ACC. Exogenous ACC (1, 10 and 100 μM) did not increase ethylene production, but the highest concentrations inhibited tissue growth. Ethylene (7 μl I−1) did not inhibit growth either when supplied as ethephon in the medium or in a continuous flow system. Benzyladenine (BA) had little effect on ethylene production, although it was necessary for sustaining the ACC level. Omission of 2.4‐dichloro‐phenoxyacetic acid (2.4‐D) from the medium caused ethylene production to increase from about 2.5 to 7 nl g−1 h−1 within the 11‐day incubation period. Although 2.4‐D did not specifically alter the endogenous level of ACC, the lowest ACC level, 33 nmol g−1, was observed in tissue treated with 2.4‐D (22.5 μM) and no BA for 11 days. Data from this treatment were used to estimate the kinetic constants for ACC oxidase, the apparent Km was 50 μM and Vmax 2.7 nl g−1 h−1. Growth of the tissue was strongly inhibited by 2.4‐D in the absence of BA, but weakly in the presence of BA (4.4 μM). The results suggest that ethylene or ACC may be involved in the induction of embryogenic tissue and in the early stages of embryo maturation.
Characterisation of chloroplast heat shock proteins in young leaves of C4 monocotyledons
Authors: Clarke Adrian K. , Critchley Christa
Published: May 2006

In vivo radiolabeling of chloroplast proteins in grain sorghum (Sorghum bicolor L. cv. Texas 610) leaves and their separation by one‐dimensional electrophoresis revealed at least 6 heat shock proteins (HSPs) between 24 and 94 kDa. of which the 24 kDa protein was the most prominent. All of these chloroplast heat shock proteins were found exclusively in the stroma. The 24 kDa heat shock protein, upon closer examination using two‐dimensional electrophoresis proved to be two similarly‐sized heat shock polypeptides with identical molecular masses and level of radiolahel incorporation, hut slightly different in isoeiectric points, suggesting isomers. Separation of stromal heat shock proteins synthesised in two other C4 monocotyledons (Punicum miliaceum L. and Umchloa panictrides L.) revealed similar putative isomers. each of 24 kDa. Several other, previously unidentified, heat shock proteins between 22 and 38 kDa were also observed in all three species. In P. miliaceum. the most prominent HSP was the pair of 24 kDa proteins, whereas in U. panicoides. it was a group of 35 to 38 kDa HSPs that was most abundant. In vivo chlorophyll fluorescence measurements showed that no sustained impairment to photosynthetic efficiency had occurred for each species after the heat stress regime. However, when cytoplasmic protein synthesis was inhibited during the high temperature treatment, a dramatic decrease was observed in photosynthetic efficiency, suggesting a possible protective role for chloroplast heat shock proteins. It was also shown that a single chloroplast HSP complex of around 380 kDa was observed in the stroma of both 5. bicolor and P. miliaceum leaves in vivo. This was in contrast to the smaller HSP complex (200–265 kDa) observed in previous studies on chloroplast heat shock proteins in Cj species.
Ageing of tomato seeds involves glutathione oxidation
Authors: De Vos C. H. Ric , Kraak H. Lieke , Bino Raoul J.
Published: May 2006

The effect of seed ageing on the oxidation of reduced glutathione (GSH) and the role of GSH oxidation in ageing‐induced deterioration were studied in seeds of tomato (Lycopersicon esculentum Mill. cv. Lerica, Moneymaker and Cromco). Both long‐term storage at 15°C/30% relative humidity (RH) and artificial ageing at 20°C/75% RH, 30°C/45% RH and 60°C/45% RH resulted in a marked loss of GSH and a simultaneous, though not proportional, increase in its oxidized form GSSG. The glutathione thiol‐disulfide status shifted towards a highly oxidized form, while the total glutathione pool decreased. The extent of GSH oxidation differed between ageing conditions and was not directly related to the extent of seed deterioration. Thiobarbituric acid‐reactive substances did not increase in ageing tomato seeds, suggesting that lipid peroxidation did not take place. Hydration of seeds, either upon imbibition in water or by priming in an osmotic solution, resulted in a rapid decrease in GSSG, a shift of the glutathione redox couple to a mainly reduced status and an increase in the glutathione pool, in both control and aged seeds. The results indicate that, in tomato seeds, (1) seed ageing involves GSH oxidation into GSSG, which is indicative of oxidative stress, (2) ageing does not affect the GSSG reduction capacity upon subsequent imbibition, and (3) the lowered viability of aged seeds cannot directly be ascribed to the decreased GSH pool or To the highly oxidized glutathione redox status.
Physiological effects of five months exposure to low concentrations of O3 and NH3 on Douglas fir (Pseudotsuga menziesii)
Authors: van Hove L. W. A. , Bossen M. E.
Published: May 2006

Three years old seedlings of Douglas fir (Pseudotsuga menziesii) were exposed lo filtered air, O3 (day and night concentrations of 78 and 30 μgm−3: respectively). NH3 (54 μg m−3) and to a mixture of NH3+O3 (day and night concentrations of 49 + 83 and 49 + 44 μg m−3 respectively), for 5 months in fumigation chambers. Both gas exchange and chlorophyll fluorescence were measured on shoots which had sprouted at the beginning of the exposure period. After 4. 8, 10 and 20 weeks of exposure, light response curves of electron transport rate (J) were determined, in which J was deduced from chlorophyll fluorescence. Net CO2 assimiialion was measured at maximum light intensity of 560) μmol m−2 S−1 (Pn.560). After 8 and 10 weeks of exposure also light response curves of CO2 assimilation were assessed.

Shoots exposed to O3 showed a reduction in net CO2 assimilation as compared to the control shoots during the entire exposure period. The reduction was related lo a lower chlorophyll content and a lower electron transport rate, whereas no effect on quantum yield efficiency (qy) was observed. In contrast, shoots exposed to NH3 showed a positive effect on photosynthesis. Shoots exposed to NH3. + O3 showed a rapid increase in Pn.560, in the period between 4 and 8 weeks to a level equal of that of the NH3‐treatment. After this period a decline in Pn.560 was observed.

After 10 weeks of exposure shoots exposed to O3 showed an increased transpiration rate in the dark as compared to the control shoots. In addition, water use efficiency (WUE) declined as a result of an increase in leaf conductance. Both observations indicate that the stomatal apparatus was affected by O3. A high transpiration rate in the dark was also found for shoots esposed to NHX. However, shoots exposed to NH3+ O3 showed neither an effect on WUE, nor an effect on transpiration rate in the dark. The possibility that NH3 delayed the O3 induced effects on photosynthesis and stomatal conductance is discussed.
Biochemical and immunological characterization of α‐amylase isoenzymes of Araucaria araucana
Authors: Acevedo Elba , Cardemil Liliana
Published: May 2006

Seven α‐amylase isoenzymes present in quiescent seeds of the South American conifer Araucaria araucana were purified by affinity chromatography and partially characterized. The molecular masses of these isoenzymes were 45.7, 47.0, 50.2, 51.2, 52.0, 53.5 and 55.2 kDa. The two main isoforms were separated from each other and from the rest of the isoenzymes by anion‐exchange chromatography using a linear gradient of 0 to 0.6 M NaCl and slightly different CaCl2 concentrations. All isoenzyme bands stained with periodic acid/dansylhydrazine, suggesting that they are glycoproteins. Electroblotting of the isoenzymes onto polyvinylidene difluoride membranes allowed determination of the amino acid composition and NH2‐terminal sequence of the 53.5‐, 50.2‐and 47.0‐kDa isoenzymes. Amino acid compositional analysis demonstrated that these enzymes are rich in glycine, aspartic acid/asparagine, alanine, serine, proline and glutamic acid/glutamine. The NH2‐terminal sequences of the three isoenzymes are identical. Comparison of the amino acid compositions and the NH2‐terminal sequence of these isoenzymes with the cereal and Vigna radiataα‐amylases demonstrated that there is no relation between them. However, polyclonal antibodies generated against barley α‐amylase cross‐reacted with all the A. araucanaα‐amylases. Peptide mapping analysis of the isoenzymes using cyanogen bromide suggests that there are genetic differences between them.
Maintenance of 32P uptake and transport in Pinus serotina seedlings under hypoxic growth conditions
Authors: Topa Mary A. , Cheeseman John M.
Published: May 2006

In the present study, we examined the effects of long‐ and short‐term hypoxia on net uptake and transport of phosphorus to shoots of pond pine (Pinus serotina Michx.), a moderately flood‐tolerant southern pine, and the influence aerenchyma formation might have in maintenance of P uptake and transport. Seedlings were grown under aerobic (250 μM O2) or hypoxic (≤50 μM O2) solution conditions for 5.3 weeks in continuously flowing solution culture containing 100 μM P. Intact seedlings were then labeled with 32P for up to 24 h to determine how short‐ and long‐term hypoxic solution conditions affected rates of unidirectional influx and the accumulation of 32P in roots and shoots. Seedlings in the long‐term hypoxic treatment were grown for 5.3 weeks in hypoxic solution and also labeled in hypoxic uptake solution. The short‐term hypoxic treatments included a 24‐h hypoxic pretreatment followed by time in labeled hypoxic uptake solution for seedlings grown under aerobic or hypoxic conditions; in the latter case, diffusion of atmospheric O2 entry into stem and root collar lenticels was blocked, thus removing any influence that aerenchyma formation might have had on enhancing O2 concentrations of root tissue. Although unidirectional influx rates of 32P in roots of seedlings grown under long‐term hypoxic conditions were 1.4 times those of aerobically grown seedlings, accumulation of 32P in roots was similar after 24 h in labeled uptake solution. These results suggest that 32P efflux was also higher under hypoxic conditions. Higher shoot/root fresh weight ratios and lower shoot P concentrations in seedlings grown under hypoxic solution conditions suggest that the “shoot P demand” per unit root should be high. Yet accumulation of 32P in shoots was reduced by 50% after 24 h in hypoxic uptake solution. Both short‐term hypoxic treatments decreased accumulation of 32P in roots by more than 50%. Short‐term hypoxia decreased shoot accumulation in seedlings grown under aerobic and hypoxic conditions by 84 and 50%. respectively. Short‐ and long‐term hypoxic conditions increased the percentage of root 32P in the nucleic acid and chelated‐P pools, resulting in a significantly smaller percentage of 32P in the soluble inorganic phosphate (pi) pool, the pool available for transport to the shoot. However, a reduction in pool size or in labeling of the pool available for transport cannot fully account for the large reduction in accumulation of 32P in shoots, particularly in the short‐term hypoxic treatment of aerobically grown seedlings. Our results suggest that both influx and transport of 32P to shoots of pond pine seedlings are O2‐dependent processes, and that the transport of 32P to shoots may be more sensitive to hypoxic solution conditions than influx at the cortical and epidermal plasmalemma, with aerenchyma formation supporting a substantial amount of both 32P uptake and transport.
Involvement of protein phosphorylation in the sensitivity of photosystem II to strong illumination
Authors: Giardi Maria T. , Komenda Josef , Masojidek Jiri
Published: May 2006

Four types of differently phosphorylated hylakoids isolated from field grown spinach (Spinacia oleracea L.) were tested for the sensitivity of photosystem II (PSII) to photoinactivation. Phosphorylation of light‐harvesting II complexes (LHCII) protected PSII electron transfer from photoinhibitory damage, while the phosphorylation of the PSII core polypeptides slightly accelerated the decline of electron transfer during high irradiance treatment. Dephosphorylation of the CP43 apoprotein and PsbH protein by an alkaline phosphatase resulted in an extreme sensitivity of the thylakoids to strong illumination. The PSII photoinactivation of thylakoids with the impaired oxygen‐evolving complex was found to be independent of phosphorylation.

The thylakoids of the thermophilic cyanobacterium Synechococcus elongates were used in order to compare the plants with an organism where LHCII complexes are missing and the PSII core proteins are not phosphorylated.
Carbohydrates are not the sole factor determining desiccation tolerance in seeds of Ambidopsis thaliana
Authors: Ooms Jaap J. J. , Wilnier Jeroen A. , Karssen Cees M.
Published: May 2006

ABA‐dcficient (aba‐1) and ABA‐insensitive (abi3–1) double mutant seeds of Arabidopsis thaliana are desiccation‐intolerant. Carbohydrates are supposed to fulfill a role in membrane protection during dehydration. Desiccation tolerance can be induced in douhle mutant seeds in vivo by supplying the ABA‐analog LAB 173 711 to the plant root system. However. this does not lead to significant changes in the carbohydrate composition, in contrast, in vitro incubation of dissected immature seeds with ABA induced desiccation tolerance concomitant with an increase in the seed raffinose content. Thus, different desiccation tolerance‐inducing treatments show contradictory effects on seed carbohydrate composition and accumulation. It is concluded that. although carbohydrates might be invohed in membrane protection or glass formation during dehydration, it is unlikely that they are the sole factor determining desiccation tolerance in Arabidopsis seeds