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Infection by eastern dwarf mistletoe (Arceuthobium pusillum) modifies needle and branch morphology and hastens white spruce (Picea glauca) mortality. We examined potential causal mechanisms and assessed the impacts of infection-induced alterations to host development and performance across scales ranging from needle hormone contents to bole expansion. Needles on infected branches (IBs) possessed higher total cytokinin (CK) and lower abscisic acid contents than needles on uninfected branches (UBs). IBs exhibited greater xylem growth than same-aged UBs, which is consistent with the promotive effect of CKs on vascular differentiation and organ sink strength. Elevated CK content may also explain the dense secondary and tertiary branching observed at the site of infection, i.e. the formation of 'witches' brooms' with significantly lower light capture efficiencies. Observed hormone perturbations were consistent with higher rates of transpiration, lower water use efficiencies (WUEs) and more negative needle carbon isotope ratios observed for IBs. Observed reductions in needle size allowed IBs to compensate for reduced hydraulic conductivity. Severe infections resulted in dramatically decreased diameter growth of the bole. It seems likely that the modifications to host hormone contents by eastern dwarf mistletoe infection led white spruce trees to dedicate a disproportionate fraction of their photoassimilate and other resources to self-shaded branches with low WUE. This would have decreased the potential for fixed carbon accumulation, generating a decline in the whole-tree resource pool. As mistletoe infections grew in size and the number of IBs increased, this burden was manifested as increasingly greater reductions in bole growth. [ABSTRACT FROM AUTHOR]

Black spruce ( Picea mariana), white spruce ( Picea glauca) and jack pine ( Pinus banksiana) were inoculated with Suillus tomentosus and subjected to potassium fluoride (1 m M KF and 5 m M KF) in the presence and absence of 60 m M NaCl. The NaCl and KF treatments reduced total dry weights in jack pine and black spruce seedlings, but they did not affect total dry weights in white spruce seedlings. The addition of 60 m M NaCl to KF treatment solutions alleviated fluoride-induced needle injury in ectomycorrhizal (ECM) black spruce and white spruce, but had little effect in jack pine seedlings. Both KF and 60 m M NaCl treatments reduced E values compared with non-treated control seedlings. However, with the exception of small reductions of Kr by NaCl treatments in black spruce, the applied KF and NaCl treatments had little effect on Kr in ECM plants. Chloride tissue concentrations in NaCl-treated plants were not affected by the presence of KF in treatment solutions. However, shoot F concentrations in ECM black spruce and white spruce treated with 5 m M KF + 60 m M NaCl were significantly reduced compared with the 5 m M KF treatment. The results point to a possible competitive inhibition of F transport by Cl. We also suggest that the possibility that aquaporins may be involved in the transmembrane transport of F should be further investigated. [ABSTRACT FROM AUTHOR]

Mortality of transplanted somatic seedlings at the stage of acclimatization is often high and likely due to rapid change in environmental conditions. To investigate the potential of in vitro acclimatization of somatic seedlings before soil transfer, somatic seedlings of white spruce (Picea glauca [Moench] Voss) were germinated on a liquid medium supplemented with sucrose. After 6 weeks in germination, sucrose was omitted from the medium for a supplementary 6 weeks at which time somatic seedlings were acclimatized in vitro in their germination tubes before transfer to soil. In vitro acclimatization of somatic seedlings was realized by transferring the test tubes containing the germinated somatic seedlings to the greenhouse for 9 days. During this period, the culture tube lids of acclimatized somatic seedlings were lifted progressively increasing air exchange between the tube and the greenhouse whereas, for non-acclimatized somatic seedlings the culture tubes were maintained closed during in vitro acclimatization. In vitro acclimatized somatic seedlings had higher asymptotic net photosynthesis (P n ) at light saturation than non-acclimatized seedlings (6 versus 4.5 µmol m-2 s-1 ). At the end of the in vitro acclimatization period, a lower rate of epidermal transpiration was also observed for acclimatized somatic seedlings (3.85 versus 4.75% h-1 ). Microscopic observations showed that starch granules were more abundant in needles of acclimatized somatic seedlings than in non-acclimatized somatic seedlings, probably as a result of their greater photosynthetic capacity. Needles from acclimatized somatic seedlings also showed more epicuticular wax projections than needles from non-acclimatized somatic seedlings. These structural changes may help somatic seedlings to restrict epidermal water loss and stomatal aperture. [ABSTRACT FROM AUTHOR]

Pyrimidine deoxyribonucleotide metabolism was investigated during maturation and germination of white spruce somatic embryos by following the metabolic fate of [2-14 C]cytidine, [2-14 C]deoxycytidine and [2-14 C]thymidine. The de-novo pathway of deoxyribonucleotides was estimated indirectly, by the ability of the tissue to incorporate cytidine into DNA after conversion to dCTP. The salvage pathway was estimated by the utilization of labelled cytidine, deoxycytidine and thymidine for synthesis of deoxyribonucleotides and nucleic acids. Utilization of cytidine for DNA synthesis, via the de novo pathway, was always lower than that observed for RNA throughout the course of the experiment. Incorporation of cytidine into RNA was found to occur either directly, after conversion to CTP, mediated by the enzymes cytidine kinase, nucleoside monophosphate kinase and nucleoside diphosphate kinase, or indirectly, after conversion to UTP via uridine and UMP. Active incorporation of uridine into RNA of white spruce-cultured cells was demonstrated previously. Salvage of deoxycytidine and thymidine was operative in maturing and germinating white spruce somatic embryos, as label from both compounds was recovered in nucleotides and DNA. However, the utilization of these precursors by the cells was different. Salvage of deoxycytidine was always higher than that observed for thymidine, which was extensively catabolized to CO2 at all stages of embryo development. [ABSTRACT FROM AUTHOR]

Pyrimidine nucleotide synthesis was investigated in isolated germinating zygotic embryos and separated megagametophytes of white spruce by following the metabolic fate of 14 C-labelled orotic acid, uridine, and uracil, as well as by measuring the activities of the major enzymes participating in nucleotide synthesis. The rate of nucleic acid synthesis in these tissues was also examined by tracer experiments and autoradiographic studies conducted with labelled thymidine, and by conventional light microscopy. From our results, it emerges that changes in the contribution of the de novo and salvage pathways of pyrimidines play an important role during the initial stages of zygotic embryo germination. Preferential utilization of uridine for nucleic acid synthesis, via the salvage pathway, was observed at the onset of germination, before the restoration of a fully functional de novo pathway. Similar metabolic changes, not observed in the gametophytic tissue, were also documented in somatic embryos previously. These alterations of the overall pyrimidine metabolism may represent a strategy for ensuring the germinating embryos with a large nucleotide pool. Utilization of 14C-thymidine for nucleic acid synthesis increased in both dissected embryos and megagametophytes during germination. Autoradiographic and light microscopic studies indicated that soon after imbibition, DNA synthesis was preferentially initiated along the embryonic axis, especially in the cortical cells. Apical meristem reactivation was a later event, and the root meristem became activated before the shoot meristem. Taken together, these results indicate that precise changes in nucleotide and nucleic acid metabolism occur during the early phases of embryo germination. [ABSTRACT FROM AUTHOR]

The present study was conducted to understand the role of sucrose in the medium on the maturation of black spruce and white spruce somatic embryos. A maturation medium containing 6% sucrose, which hydrolyzed into glucose and fructose, gave significantly more embryos than a medium containing 3.16% of each glucose and fructose. Preventing the complete sucrose hydrolysis by a daily transfer of the tissues onto fresh medium significantly decreased the yield of somatic embryos compared to when sucrose was allowed to complete its hydrolysis. This reduction was not due to the manipulation of the tissues during the transfer, since a daily in situ transfer did not affect embryo production. To verify if the better embryo production observed on a medium containing 6% sucrose was due to the increasing osmotic pressure of the medium, this increasing osmotic pressure was simulated with a sequence of media containing different concentrations of glucose and fructose. Unexpectedly and for both species, this simulation did not improve somatic embryo production, which stayed similar to the one obtained on constant osmotic pressure. To understand these results, embryos produced on the different treatments were analyzed in terms of sucrose, glucose, fructose and starch levels and protein contents. The embryo carbohydrate content was independent from the carbohydrate used in the maturation medium. However, embryos matured on 6% sucrose allowed to hydrolyze during the maturation period contained significantly more soluble and insoluble proteins than embryos matured on any other treatment. Furthermore, embryos with a higher protein content also exhibited a higher epicotyl appearance frequency. The role of sucrose as a regulatory factor during the maturation of spruce somatic embryos is discussed. [ABSTRACT FROM AUTHOR]

Changes in ascorbic acid (AA) metabolism were investigated in 3 different cell lines of white spruce; a non-embryogenic line (NE)WS and two embryogenic lines with low (E)WS1 and high (E)WS2 percentage of embryo germination. During embryo maturation, a high AA/dehydroascorbate (DHA) ratio was observed in the two embryogenic cultures. The increment of this ratio was mainly ascribed to the high ability of the (E)WS1 and (E)WS2 lines to generate AA from its last precursor, l-galactono-γ-lactone, since no increase in the activities of the AA-recycling enzymes, i.e., AA free-radical reductase (AFRR) and DHA reductase (DHAR), was observed as the embryos developed. During the partial drying treatment needed for successful embryo germination, the ability to de novo generate AA continued to increase in the embryos of the two embryogenic lines, although the total ascorbate pool (AA+DHA) sharply decreased. A reactivation of the overall AA metabolism was observed at the inception of germination, especially in the (E)WS2 embryos. These results suggest that (1) the ability to metabolically alter the AA/DHA ratio may be a fundamental requirement for somatic embryo maturation and (2) the restoration of the AA metabolism during the first days of germination may be necessary for successful embryo germination. [ABSTRACT FROM AUTHOR]

The imposition of a partial drying treatment (PDT) on mature white spruce somatic embryos is a necessary step for successful germination and embryo conversion into plantlets. Purine and pyrimidine metabolism was investigated during the PDT of white spruce somatic embryos by following the metabolic fate of 14C-labeled adenine, adenosine, and inosine, as purine intermediates, and orotic acid, uridine, and uracil, as pyrimidine intermediates, as well as examining the activities of key enzymes. Both the salvage and the degradation pathways of purines were operative in partially dried embryos. Adenine and adenosine were extensively salvaged by the enzymes adenine phosphoribosyltransferase and adenosine kinase, respectively. The activity of the former enzyme increased during the PDT. In both mature and partially dried embryos, a large proportion of inosine was recovered as degradation products. The de novo pathway of pyrimidine nucleotide biosynthesis, estimated by the incorporation of orotic acid into the nucleotides and nucleic acids, was high at the end of the maturation period and declined during the PDT. Uridine was the main substrate for the pyrimidine salvage pathway, since a large proportion of uracil was recovered as degradation products, i.e. CO2 and β-ureidopropionic acid in both mature and partially dried embryos. Uridine was mainly salvaged by uridine kinase, whose activity was found to increase during the PDT. Taken together these results indicate that the PDT might be required for increasing the activity of adenine and uridine salvage enzymes, which could contribute to the enlargement of the nucleotide pool required at the onset of germination. [ABSTRACT FROM AUTHOR]

In white spruce (Picea glauca [Moench.] Voss.) seeds, the raffinose family oligosaccharides (RFOs) provide carbon reserves for the early stages of germination prior to radicle protrusion. Some seedlots contain seeds that are dormant, failing to complete germination under optimal conditions. Since dormancy may be imposed through a metabolic block in reserve mobilization, the goal of this project was to identify any impediment to RFO mobilization in dormant relative to nondormant seeds. Desiccated seeds contain primarily, and in order of abundance on a molar basis, sucrose and the first 3 members of the RFOs, raffinose, stachyose and verbascose. Upon radicle protrusion at 25°C, the contents of RFOs decreased to low amounts in all seed parts, regardless of prior dormancy status and sucrose was metabolized to glucose and fructose, which increased in seed parts. During moist chilling at 4°C, RFO content initially decreased before stabilizing and then increasing. In seeds that did not complete germination, the synthesis of RFOs at 4°C favored verbascose, so that at the end of 14 (nondormant) or 35 (dormant) weeks, verbascose contents in megagametophytes exceeded the amount initially present in the desiccated seed. This was also true in the embryos of the dormant seedlot. In seed parts from both seedlots after months of moist chilling, stachyose amounts exceeded raffinose amounts. Upon radicle protrusion at 4°C, RFO contents decreased to amounts most similar to those present in seeds that completed germination at 25°C. Hence, the RFOs are utilized as a source of energy, regardless of the temperature at which white spruce seeds complete germination. Based on the similarity of sugar contents in seed parts between dormant and nondormant seeds that did not complete germination, differences in sugar metabolism are probably not the basis of dormancy in white spruce seeds. [ABSTRACT FROM AUTHOR]

The objective of the current investigation was to study the role of ethylene in the maturation of white spruce (Picea glauca [Moench.] Voss) somatic embryos. This was carried out by examining the effects of (1) 1-aminocyclopropane-1-carboxylic acid (ACC), a direct precursor of ethylene in plant tissue, (2) silver nitrate (AgNO3), an inhibitor of ethylene action, (3) α-aminooxyamino acid (AOA), a potent inhibitor of ethylene biosynthesis, and (4) enrichment with ethylene. Ethylene biosynthesis was biphasic and gradually increased during embryo development, whereas endogenous ACC and N-malonylaminocyclopropane-1-carboxylic acid (mACC) decreased. Addition of ACC or AOA to the culture medium increased or decreased, respectively, ethylene biosynthesis by altering endogenous ACC levels during the culture period. In contrast to AOA and AgNO3, ACC and ethylene enrichment significantly decreased the production of mature somatic embryos and increased the browning of the cultures. However, the structure of the shoot apex in mature cotyledonary stage embryos formed under ethylene enrichment was similar to that in control systems. This shows that a reduction in ethylene is beneficial to maturation of white spruce somatic embryos. This is further substantiated by the finding that the inhibitory effects of AOA were partially reversed by the addition of ethylene. The possible effects of the interaction between ethylene and polyamines on somatic embryo development are also discussed. [ABSTRACT FROM AUTHOR]

In order to examine the biosynthesis, interconversion, and degradation of purine and pyrimidine nucleotides in white spruce cells, radiolabeled adenine, adenosine, inosine, uracil, uridine, and orotic acid were supplied exogenously to the cells and the overall metabolism of these compounds was monitored. [8-14C]adenine and [8-14C]adenosine were metabolized to adenylates and part of the adenylates were converted to guanylates and incorporated into both adenine and guanine bases of nucleic acids. A small amount of [8-14C]inosine was converted into nucleotides and incorporated into both adenine and guanine bases of nucleic acids. High adenosine kinase and adenine phosphoribosyltransferase activities in the extract suggested that adenosine and adenine were converted to AMP by these enzymes. No adenosine nucleosidase activity was detected. Inosine was apparently converted to AMP by inosine kinase and/or a non-specific nucleoside phosphotransferase. The radioactivity of [8-14C]adenosine, [8-14C]adenine, and [8-14C]inosine was also detected in ureide, especially allantoic acid, and CO2. Among these 3 precursors, the radioactivity from [8-14C]inosine was predominantly incorporated into CO2. These results suggest the operation of a conventional degradation pathway. Both [2-14C]uracil and [2-14C]uridine were converted to uridine nucleotides and incorporated into uracil and cytosine bases of nucleic acids. The salvage enzymes, uridine kinase and uracil phosphoribosyltransferase, were detected in white spruce extracts. [6-14C]orotic acid, an intermediate of the de novo pyrimidine biosynthesis, was efficiently converted into uridine nucleotides and also incorporated into uracil and cytosine bases of nucleic acids. High activity of orotate phosphoribosyltransferase was observed in the extracts. A large proportion of radioactivity from [2-14C]uracil was recovered as CO2 and β-ureidopropionate. Thus, a reductive pathway of uracil degradation is functional in these cells. Therefore, white spruce cells in culture demonstrate both the de novo and salvage pathways of purine and pyrimidine metabolism, as well as some degradation of the substrates into CO2. [ABSTRACT FROM AUTHOR]

ABA analog structure-function relationships were determined by testing an array of 19 different ABA analogs on 1-year-old clonal white spruce (Picea glauca [Moench.] Voss) raised from somatic embryos. The contribution of specific structural features to analog activity was determined from the relative effect of aeroponically applied analog solutions (10-3 M) on seedling gas exchange. Seedling transpiration rate (E) and carbon assimilation rate (A) were measured continuously during treatment by means of a whole plant cuvette system. The analogs were racemic about the C-1′ chiral center and were derived from changes imposed on six regions of the ABA molecule. The activity of optically pure (+)-S-ABA and (-)-R-ABA were also determined. Analog activity was reduced by changing the oxidation level at C-1 from the carboxylic acid. The ring C-2′, C-3′ double bond was important but not essential to activity. The activity lost through changes in ring structure and C-1 oxidation level was, in many cases, almost fully restored by replacing the C-4, C-5 double bond with a triple bond. Therefore, analogs with a triple bond at C-4 were more active than their equivalents with a dienoic side chain. Fluorination of the C-7′ methyl caused a relatively moderate reduction in analog activity. Truncation of C-1 and C-2 from the side chain reduced activity to near zero. The unnatural (-)-ABA enantiomer was inactive. [ABSTRACT FROM AUTHOR]

The fate of carbamoyl phosphate in white spruce seedlings revolves around the production of spontaneous degradation products, cyanate, bicarbonate, and carbamate. When [14C]-carbamoyl phosphate and [14C]-cyanate are assimilated, urea is a common early metabolic intermediate that appears in the alcohol soluble N, By contrast, urea is not detected among the products of [14C]-bicarbonate. Carbamoyl phosphate and glutamic acid are implicated as having pivotal roles in the production of amides, arginine, and biotin. Within 2-h exposures to radioactive substrates considerably more carbon from bicarbonate was diverted into amino acids incorporated into proteins than with carbon-nitrogen substrates. Specific activities of bound amino acid residues support the view that proteins formed from these [14C]-substrates have different rates of metabolic turnover. [ABSTRACT FROM AUTHOR]

White spruce [Piceae glauca(Monech Voss] seedlings were pre-conditioned by Cold storage and root pruning and a study was made of the effects of conditioning on root regeneration and stomatal adaptation following transplanting. Root pruning (0 to 75% of the initial root area) of dormant seedlings immediately prior to transplanting did not confer any detectable physiological advantage in either cold-stored or freshly-lifted seedlings. Transpiration rates and stomatal resistance were not greatly affected by root pruning in the 6 week period after planting and root pruning did not greatly alter the response to drought. Cold-stored seedlings appear better able to avoid transplanting shock and an early drought despite delayed root growth as evidenced by a) a delay in flushing of new shoot growth and b) pre-conditioning of the stomatal apparatus which reduced water loss after planting and when moisture was limiting. Seedlings freshly-lifted in the spring did not show these adaptive responses and their stomata were poorly adapted to reduce water loss in the post-planting period after a drought. [ABSTRACT FROM AUTHOR]

Needle hardiness of introduced yellow pine, Pinus banksiana Lamb., lodgepole pine, P. contorta Dougl. and native white spruce, Picea glauca (Moench) Voss, were assessed by the effective prefreezing temperature method. Yellow pine needles were less hardy than lodgepole pine or white spruce needles in Alaska on each date measured. Although hardiness decreased in springtime in all species, decreases in hardiness in yellow pine began before temperatures were above -20°C, apparently in response to day length, while decreases in hardiness in lodgepole pine and white spruce began only when mean temperatures were above 0°C. Hardiness was increased by decreasing the water content of yellow pine and spruce needles. However, only the latter increased its field hardiness by decreased water contents, and only to a small degree. Large decreases in phospholipid occurred during the dehardening period, indicating the presence of major membrane-associated changes. However, changes in hardiness did not closely parallel those in phospholipid; hardiness decreased before phospholipid did in spruce and after phospholipid did in lodgepole pine. In yellow pine, changes in hardiness were more closely related to changes in phospholipid content. Decreases in phospholipid appeared to be correlated with the day length in all species. [ABSTRACT FROM AUTHOR]

It is not known how embryos of seeds of the Pinaceae protrude from their enclosing tissues to complete germination. Prior to protrusion of the radicle there is an increase in endo-β-1,4-mannanase (EC 3.2.1.78) activity associated with weakening of the micropylar megagametophyte/nucellus from seeds of white spruce (Picea glauca [Moench.] Voss). Mannanase activity is present as three isoforms (pI values 5.0, 4.8, 4.7) in both the embryo and surrounding structures (megagametophyte and nucellus) prior to and during imbibition. Activity of all the isoforms increases in the chalazal and micropylar megagametophyte during germination. Activity then declines after the testa splits, typically 1 day prior to radicle protrusion, due partially to its leaching from the seed into the surrounding water. Activity increases in the cotyledons and axis as the embryo commences elongation. Seeds from dormant seedlots exhibit a lower germination percentage, relative to seeds from nondormant seedlots, and the force necessary for the embryo to puncture the surrounding structures tends to be greater. Although similar mannanase activities are present in unimbibed seeds of dormant and nondormant seedlots, during germination, enzyme activity in seeds of dormant seedlots is lower. Moist chilling alleviates dormancy in the seeds of the Pinaceae and, during 3 weeks of this treatment, mannanase activity slowly increases. After 3 weeks of moist chilling and regardless of whether the seedlot was dormant or not prior to moist chilling, the force necessary to puncture the micropylar megagametophyte and nucellus is lower, and the speed of germination greater. Seeds from previously dormant seedlots also complete germination to a greater percentage, relative to unchilled seeds from dormant seedlots. Upon transfer to 25°C, mannanase activity in moist-chilled seeds decreases during germination of all seedlots regardless of their previous dormancy status. [ABSTRACT FROM AUTHOR]

White spruce [ Picea glauca (Moench) Voss.] seedlings were used to study the changes in cell wall composition and elasticity in mature needles before and after the resumption of growth following winter dormancy. Dormant seedlings showed high cell wall elasticity that decreased after the resumption of shoot growth. Cell wall hemicellulose content increased 3 days after planting and decreased after the buds flushed. Non-cellulosic glucose and arabinose were the sugars showing the most pronounced changes related to shoot growth. Arabinose was the most abundant sugar residue in the pectin and hemicellulose fractions and it decreased until day 10 after planting. At the same time, the levels of glucose in pectin and hemicellulose increased. The results provide evidence for cell wall carbohydrate turnover in dormant and active seedlings before and after bud flushing. [ABSTRACT FROM AUTHOR]

Endogenous free abscisic acid (ABA), indole-3-acetic acid (IAA) and gibbercilins (Gas) were identified and quantified in whole white spruce (Picea glauca [Moench] Voss) seeds, zygotic embryos and megagametophytes by high performance liquid chromatography and gas chromatography-selected ion monitoring-mass spectrometry. In seeds, the ABA content was high at the early embryo developmental stage and underwent a further rapid increase at the precotyledonary stage about 4 weeks after pollination (AFP). This latter increase in ABA corresponded with an increase in seed dry weight 4-6 weeks AFP. Increases of ABA continued until the late maturation stage (8 weeks AFP). The endogenous ABA concentration on a dry weight basis was higher in embryos than in megaganictophytes. but the total ABA content per structure was lower in embryos than in megagametophytes because the size and weight of these two structures were different. At the late maturation stage, ABA amounts decreased earlier in embryos (8 weeks AFP) than in megagametophytes (10 weeks AFP). Low concentrations of ABA were observed in embryos and megagametophytes of stored seeds. During development, the endogenous IAA amount in the megagametophytes declined after pollination. This was followed by an increase from 2 to 6 weeks AFP. During late maturation, the IAA content increased in megagametophytes but decreased in the embryos. Throughout seed development, GA4 slightly decreased while GA9 increased. Endogenous GA7 remained very low throughout. In stored seeds, amounts of both IAA and Gas were lower than in developing seeds. Concomitant with a rapid increase in seed dry weight, seed moisture content (MC) decreased sharply between precotyledonary stage and early cotyledonary stage (4 and 6 weeks AFP). Seeds could absorb water and germinate after a significant decrease of MC and at a high endogenous ABA content (8 weeks AFP). These results suggest that endogenous ABA. IAA and GAs are involved in white spruce embryogenesis. There are relatively high ABA and IAA contents in the embryo environment but the GAs checked in this study are low. [ABSTRACT FROM AUTHOR]

Seedlings of white spruce (Picea glauca [Moench] Voss.) were treated with triadimefon solution applied to the soil, and their early responses studied from 12 h to 7 days after treatment. Transpiration rates declined and respiration rates increased immediately after the commencement of triadimefon treatment. Photosynthetic rates declined less than transpiration rates, resulting in an increase in water use efficiency, whereas root and shoot water potentials remained unchanged during the first 5 days of triadimefon treatment. Triadimefon decreased root hydraulic conductivity and inhibited the activity of the plasma membrane ATPase. In addition, triadimefon-treated roots drastically increased the ratios between tree sterols and sterol esters and decreased the ratios between sterol esters and acylated sterol glycosides. [ABSTRACT FROM AUTHOR]

In vitro cultures and endogenous abscisic acid (ABA) analyses with gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) were used to study the effects of AgNO3 and polyethylene glycol (PEG) on white spruce (Picea glauca) somatic embryo maturation and endogenous ABA contents. Normally, in the absence of ABA, white spruce somatic embryos cannot mature. However, AgNO3and PEG stimulated somatic embryo maturation by increasing the number of cotyledonary embroyos. A combination of 100 μM AgNO3 and 40 g l-1 PEG was the treatment that was most effective in enhancing cotyledonary embryo formation without exogenous ABA. Either AgNO3 or PEG was able to increase endogenous ABA levels of the embryogenic culture but a combination of AgNO3and PEG was the most effective treatment. Stimulation of cotyledonary embryo formation by AgNO3 occurred only at low ABA levels, while PEG promoted embryo formation at all exogenous ABA concentrations. Germination tests indicated that AgNO3 had no negative effects on embryo germination and conversion while the PEG-treated embryos failed to germinate. [ABSTRACT FROM AUTHOR]

White spruce [Picea glauca (Moench) Voss.] seedlings were grown in solution culture and treated with 20 mg l-1 triadimefon [1-(chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazol-1-yl)-2-butanol] for 4 weeks and then subjected to osmotic stress with polyethylene glycol 3350. Water potentials and electrolyte leakage were measured in control and triadimefon-treated seedlings before and after the plants were subjected to osmotic stress. The plasma membranes were isolated from needles to study their lipid composition and the activity of plasma-membrane bound ATPase. Triadimefon treatment reduced water potentials and increased leakage of electrolytes from seedlings. However, when the seedlings were exposed to osmotic stress, triadimefon-treated plants maintained higher water potentials and leaked less electrolytes compared with the control plants. Both triadimefon and osmotic stress treatments inhibited the activity of plasma membrane-bound ATPase and altered the composition of free sterols in the plasma membranes. Triadimefon-treated plants contained traces of campesterol, which was not present in control. Osmotic stress drastically reduced phospholipid:protein and sterol:protein ratios and increased sterol:phospholipid ratios in the plasma membranes. [ABSTRACT FROM AUTHOR]

Interactions between growth temperature and measurement temperature were examined for their effects on white spruce [Picea glauca (Moench) Voss] root respiration. Total dark respiration rates increased with measurement temperature and were unaffected by growth temperature. Partitioning of respiratory electron flow between the cytochrome and alternative pathways was also unaffected by growth temperature. The proportion of respiration mediated by the alternative pathway was constant at measurement temperatures between 4°C and 18°C, but was increased at higher temperatures. Changes in alternative pathway activity were paralleled by changes in capacity, and the alternative pathway was almost fully engaged at all temperatures. Roots grown at low temperature displayed higher carbohydrate levels than roots grown at higher temperatures, but respiration rate was unaffected. Spruce root respiration did not appear to acclimate to growth temperature, and the alternative pathway was not preferentially engaged at tow temperature. [ABSTRACT FROM AUTHOR]

Low levels of mannitol (2-6%) promoted the formation of globular embryos in embryogenic cultures of interior spruce (Picea glauca engeimanni complex). However, these concentrations of mannitol were inhibitory to the formation of cotyledonary embryos. A short (1 week) pulse of mannitol in combination with abscisic acid doubled the production of late cotyledonary somatic embryos compared with the standard abscisic acid treatment. Higher levels of mannitol (13 and 20%) were required to inhibit precocious germination of spruce somatic embryos. These concentrations of mannitol promoted the accumulation of storage proteins during cotyledon maturation, but were not as effective as abscisic acid. Furthermore, 13 and 20% mannitol treatments did not substitute for abscisic acid in promoting the formation of cotyledonary embryos. Pre-treatment of late cotyledonary embryos with mannitol (13-25%) did not increase the frequency of germination compared with germination in non-treated embryos (approximately 10% germinated) although dehydration with high relative humidity treatment increased germination to 83%. [ABSTRACT FROM AUTHOR]

Storage proteins of interior spruce (Picea glauca engelmanii complex) somatic embryos were compared to those of zygotic embryos by sodium dodecyl sulphatepolyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Somatic embryos contain the same storage proteins as zygotic embryos based on similarities of molecular weight, isoelectric variants, solubility characteristics and disulfide linkages. Storage protein levels varied among different somatic embryo genotypes; however, all genotypes tested accumulated significant amounts of storage proteins. Zygotic and somatic embryos display a similar developmental accumulation of storage proteins. The 22, 24, 33 and 35 kDa proteins appear in early stage embryos, while the 41 kDa protein begins to accumulate during mid cotyledon development. The 22, 24 and 41 kDa proteins accumulate continuously during cotyledon development in somatic embryos cultured on abscisic acid. In contrast, zygotic embryos display a more rapid and transient accumulation of these proteins. [ABSTRACT FROM AUTHOR]

White spruce [Picea glauca (Moench) Voss] seedlings were preconditioned by subjecting them to 3 cycles of a mild drought stress. After 1 week of stress relief their water status, soluble carbohydrate content and cell wall composition in newly formed needles were examined and compared with those in control seedlings. Both preconditioned and control seedlings were subsequently subjected to a severe drought stress and again analyzed, Preconditioning treatment both before and during subsequent stress exposure lowered osmotic potentials at full hydration, and after the loss of turgor, decreased lignin content and increased heinicellulose content of the cell walls. Severe drought had similar but more drastic effects on seedling water relations,, sugar accumulation and cell wall hemicellulose content; it also decreased cell wall pectin levels. The decrease in pectin levels was accompanied by a loss of galactose and glucose from pectic substances. Little change in cellulose con tent was observed as a result of preconditioning and severe drought. [TRANSLATION]

Buffer-soluble proteins that have subunit molecular weights, in the presence of sodium dodecyl sulphate (SDS), of 47, 31 and 27 kilodaltons (kDa) form the major storage proteins in the mature white spruce [Picea glauca (Moench) Voss] seed. These proteins were found mainly in the megagametophyte, but smaller amounts were identified in the embryo. Following the completion of germination, this reserve was rapidly hydrolyzed in both tissues and probably plays a major nutritional role in the germinated seed. Buffer-insoluble proteins were also found in megagametophytes and embryos from the mature seed. These proteins were soluble in buffer only if SDS was present. Predominant in this class of proteins were several that have a subunit molecular weight and structure that is characteristic of seed crystalloid storage proteins; the subunits were shown to be heterodimers with polypeptide molecular weights in the 33 kDa to 37 kDa and 23.5 kDa to 25 kDa ranges. This reserve was rapidly hydrolyzed in the germinated seed. Storage protein hydrolysis was accompanied by a significant increase in the soluble amino acid pool in both megagametophytes and embryos. Cell-free extracts of mature seed megagametophytes and embryos contained leucine-naphthylamidase (leuNAase) activity. Following germination, this activity was maintained at a constant level in megagametophytes but increased substantially in embryos. [ABSTRACT FROM AUTHOR]

Plantlets were regenerated from long‐term embryogenic cultures of Picea glauca (Moench) Voss. (White spruce). Embryogenic calli, initiated from immature zygotic embryos and maintained by monthly subculture for 16 months, were used to establish suspension cultures. Small somatic embryos were continuously produced in liquid culture medium containing auxin and cytokinin and the cultures showed a sustained regeneration capacity for >6 months. Somatic embryos propagated in the suspension cultures developed further into embryos bearing cotyledons, about 1 month after transfer to solidified medium containing abscisic acid. Electron microscopic examination revealed that storage nutrients, lipids, proteins and carbohydrates, accumulated in the somatic embryos during this treatment with abscisic acid (ABA). Upon subculture to medium lacking plant growth regulators such embryos could develop into small green plantlets. [ABSTRACT FROM AUTHOR]

Rates of photosynthesis were measured for shade-adapted conifer needles [Picea abies (L.) Karst., Picea glauca (Moench) Voss, Picea mariana (Mill.) B.S.P., Picea sitchensis (Bong.) Can., Pinus sylvestris L.] illuminated on i) their top surface, ii) their top and bottom surfaces simultaneously, or iii) uniformly in a light integrating sphere. The rate of bending of the light response curve of photosynthesis was strongly correlated with the amount of chlorophyll per unit of illuminated leaf area, when the amounts of chlorophyll were above 200mg m-2. Below 200mg -2 only small differences in the rate of bending occurred and the light response curves took the form of a quasi-Blackman response. At chlorophyll contents below 200 mg -2 the rate of bending of the light response curves was insignificantly different from a mean published value for eazymatically isolated cells of angiosperm leaves (I. Terashima and T. Saeki. Ann. Bot. 56: 489-499, 1985). The apparent quantum yield of photosynthesis (based on incident light) also showed a response to chlorophyll content not different from the pattern reported for angiosperm leaves (E. K. Gabrielsen. Physiol. Plantarum 1: 5-37, 1948). Neither CO2 nor O2 concentration significantly affected the rate of bending of the light response curves. It is concluded that the light response curve of individual chlorenchyma cells is a quasi-Blackman response and that the rate of bending of the light response curve of intact leaves is a strong function of the development of gradients of light and thus the chlorophyll content of leaves. [ABSTRACT FROM AUTHOR]

The spectrophotometrically‐determined activity of NAD+‐malate dehydrogenase (MDH, EC 1.1.1.37) from white spruce [Picea glauca (Moench) Voss] needles was assayed with NADH and oxaloacetate. Activity was very low when extracted with only acetate buffer (pH 5.4), phosphate buffer (pH 6.8), or Tris‐HCl buffer (pH 8.0). However, activity increased from 1 to over 200 μmol (g dry weight)‐1 min‐1 with the addition of polymers such as polyvinylpyrrolidone (PVP) and polyethylene glycol (PEG) and the detergents, Tween 80, Tergitol 15‐S‐9 and Triton X‐100. Best activity was observed when extracted in a buffer at pH 6.8 and with 1% (v/v) for the three detergents and PEG, and 6% (w/v) for PVP. MDH activity decreased with age of the needles on the tree. Six‐year‐old needles contained only about one‐fifth of the activity of current year, fully‐expanded needles. The main decrease in enzyme activity was observed in one‐year‐old needles. Protein content obtained from needles extracted with just phosphate buffer (pH 6.8) was very low, but increased greatly when the above chemicals were added to the buffer. In contrast with needles, extracts of vegetative buds contained much higher levels of MDH and protein when extracted with only phosphate buffer (pH 6.8). Although MDH activity in needle extracts declined with storage of the extracts at 4°C in the dark for 6 days, the decrease was least for buffers containing a combination of different protective agents. [ABSTRACT FROM AUTHOR]