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PubMed1993

Carbohydrate reserve accumulation and depletion in Engelmann spruce (Picea engelmannii Parry): effects of cold storage and pre-storage CO(2) enrichment.

The effects of pre-storage CO(2) enrichment on growth, non-structural carbohydrates and post-storage root growth potential of Engelmann spruce (Picea engelmannii Parry) seedlings were studied. Seedlings were grown from seed for 202 days in growth chambers with ambient (340 micro l l(-1)) or CO(2) enriched (1000 micro l l(-1)) air. Some seedlings were transferred between CO(2) treatments at 60 and 120 days. Photoperiod was reduced at 100 days to induce bud set and temperature was reduced at 180 days to promote frost hardiness development for storage at -5 degrees C for 2 or 4 months. Stored seedlings were planted in a growth chamber after thawing for one week at +5 degrees C. At 80, 120, 140 and 202 days, and at each planting time after storage, seedlings were harvested for growth measurements and analysis of starch and soluble sugar concentrations. Planted seedlings were assessed for bud break every two days and new roots > 5 mm long were counted after four weeks. Carbon dioxide enrichment increased root collar diameter and almost doubled seedling biomass, with the most obvious effects occurring after bud set. Stem height was affected only slightly and shoot/root ratios were not affected at all. Carbon dioxide enrichment increased the rate of reserve carbohydrate accumulation, but did not influence the final concentration attained before storage (accounting for 32% of seedling dry weight). Needles were the major storage organ for soluble sugars, whereas roots were the major storage organ for starch. Soluble sugars were not strongly affected by two or four months of storage, but starch was reduced by more than 50% in all plant parts. None of the CO(2) treatments had an impact on bud break or root growth potential.

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PubMed1993

Effects of elevated carbon dioxide and drought on the growth and physiology of clonal Sitka spruce plants (Picea sitchensis (Bong.) Carr.).

Two-year-old Sitka spruce (Picea sitchensis (Bong.) Carr.) plants from four clones were grown in naturally lit growth chambers for 6 months at either ambient (350 ppm) or ambient + 250 ppm (600 ppm) CO(2) concentration. Plants were grown in large boxes filled with peat, in a system that allowed the roots of individual plants to be harvested easily at the end of the growing season. Half of the boxes were kept well watered and half were allowed to dry out slowly over the summer. Plants growing in elevated CO(2) showed a 6.9% increase in mean relative growth rate compared to controls in the drought treatment and a 9.8% increase compared to controls in the well-watered treatment, though there was considerable variation in response among the different clones and water treatments. Rates of net CO(2) assimilation were higher and stomatal conductances were lower in plants grown in elevated CO(2) than in ambient CO(2) in both the well-watered and drought treatments. Both of these factors contributed to the doubling of instantaneous water use efficiency. The partitioning of biomass to roots was unaffected by elevated CO(2), but the ratio of needle mass/stems + branches mass decreased. Together with reduced stomatal conductance, this probably caused the observed increases in xylem pressure potentials with elevated CO(2).

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PubMed1994

Heat-shock response of Pinus and Picea seedlings.

The effect of a short period of elevated temperature, or heat shock, on protein synthesis was investigated in 2-day-old seedlings of jack pine (Pinus banksiana Lamb.), loblolly pine (P. taeda L.), lodgepole pine (P. contorta Dougl.), black spruce (Picea mariana (Mill.) BSP), and white spruce (P. glauca (Moench) Voss.). In all species, heat shock led to increased [(35)S]methionine incorporation into heat-shock proteins (hsp's) with molecular masses of 83 and 72 kDA. Heat shock also induced synthesis of several low molecular weight proteins that were absent from control seedlings. The low molecular weight hsp's produced by pine seedlings had molecular masses of 27, 24.6, 20.5 and 17.5 kDa, whereas those produced by spruce seedlings had molecular masses of 27.2, 19.8, 18.4, 17.2 and 16.0 kDa. All of the low molecular weight hsp's showed isoelectric variants. Heat shock led to increased [(35)S]methionine incorporation into a group of low molecular weight hsp's that were also present in control seedlings.

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PubMed1994

Relationships between nutrient supply, nitrogen partitioning and growth in young Sitka spruce (Picea sitchensis).

Budget studies have shown that internal cycling may contribute a large proportion of the annual nutrient supply required to support new growth in trees. Use of budgets to quantify internal cycling only quantifies the net transfer of nutrients within the plant. Differential partitioning of remobilized nutrients and current nutrient uptake could lead to errors in the interpretation of results from these studies. We have quantified the dynamic relationships among tree growth, nutrient uptake and internal cycling by labeling the current uptake of N in trees that received contrasting amounts of nutrient. Two-year-old seedlings of Sitka spruce (Picea sitchensis (Bong.) Carr.) were grown in sand culture in a greenhouse for one year. The trees received nutrients in a balanced solution at either a high (high-RAR) or a low (low-RAR) relative addition rate throughout the experiment. Current N uptake was labeled with (15)N from April 13 to July 25. Thereafter, trees were re-potted in clean sand and unlabeled N applied until November 13. Overall growth was sustained for approximately 10 weeks before treatment effects were observed. Initially, no differences in the partition of growth or remobilized N occurred, although partition of current uptake favored the roots of plants in the low-RAR treatment. After 6 weeks, the partition of both growth and remobilized N altered in favor of roots of plants in the low-RAR treatment. Nutrient supply had no effect on the amount or rate of N remobilization. No evidence was found to suggest that N taken up in the current season and partitioned to preexisting shoots or roots is remobilized late in the season to support growth of new shoots. However, some trees in the high-RAR treatment exhibited a second flush of growth later in the season that was partially sustained by remobilization of (15)N from current shoots formed earlier in the season. Use of (15)N demonstrated differential partitioning of current uptake and remobilized N. The results highlight the limitations of simple budget studies for quantifying internal cycling.

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PubMed1994

Structural scaling of light interception efficiency in Picea engelmannii and Abies lasiocarpa.

Sunlight interception efficiency was compared at the leaf, shoot, branch and crown levels for Picea engelmannii (Parry) and Abies lasiocarpa ((Hook.) Nutt.), dominant tree species of the central Rocky Mountains, USA. The ratio of silhouette to total leaf area (STAR) was used to quantify the efficiency of direct-beam sunlight interception at each structural scale. Total mean reductions in STAR from the leaf to the crown level were 0.39 to 0.06 in P. engelmannii and 0.46 to 0.02 in A. lasiocarpa. These reductions in STAR occurred for both species as structural scale increased due to a more upright leaf inclination, increased leaf twisting and curvature, or greater mutual shading among plant structures. A steeper leaf inclination between the leaf and shoot level accounted for 26 +/- 19% (95% C.I.) of the total leaf-to-crown STAR reduction; mutual shading among leaves on shoots caused a 14 +/- 7% reduction, whereas leaf curvature and twisting accounted for 22 +/- 3% for a total reduction of 62 +/- 8%. The STAR varied slightly from the shoot to the branch level (+/- 7%) except for a 26% reduction in shade shoots of A. lasiocarpa as a result of increased mutual shading among leaves at lateral nodes. Another substantial reduction in STAR occurred from the branch to the crown level (35 +/- 3% of total) as a result of shading of one branch layer by another within the crown. Thus, light interception efficiency decreased as structural scale increased in both species, especially from the leaf to the shoot level and from the branch to the crown level.

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PubMed1994

Effects of manganese deficiency on soluble apoplastic peroxidase activities and lignin content in needles of Norway spruce (Picea abies).

Apoplastic peroxidase activities were investigated in manganese-deficient and manganese-sufficient needles of field-grown Norway spruce trees (Picea abies L.). In Mn-sufficient needles, two sets of peroxidases, one with an alkaline pI >/= 9 and another with an acidic pI </= 3, were identified using guaiacol or coniferylalcohol as substrates for activity staining after isoelectric focusing in a pH gradient from 3 to 9. The acidic peroxidases were capable of Mn-dependent NADH oxidation and H(2)O(2) formation. Syringaldazine peroxidase activity was not found in apoplastic extracts, but was present in whole-needle extracts. Manganese deficiency did not affect the activity or the isoelectric focusing pattern (pH 3 to 9) of the apoplastic peroxidases. Soluble peroxidase activities from whole-needle extracts were significantly higher in Mn-deficient than in Mn-sufficient needles with all substrates tested. Mn-deficient needles contained slightly less cell wall material than Mn-sufficient needles, but the lignin content was similar. Neither apoplastic peroxidase activity nor lignification was affected by Mn deficiency, suggesting that apoplastic peroxidases are regulated independently from symplastic peroxidases.

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PubMed1994

Effect of elevated temperatures on carbon dioxide exchange in Picea rubens.

We examined some of the physiological reasons that may underlie past and expected future migrations of red spruce (Picea rubens Sarg.) by evaluating the effects of high temperatures on photosynthesis and respiration of trees growing on Whiteface Mountain, NY. At temperatures of 35-40 degrees C, the trees exhibited a zero or negative carbon balance. Higher temperatures resulted in cellular disorganization and death. Temperatures around 30 degrees C resulted in reduced CO(2) uptake, a condition that could decrease future reproductive output and competitive stature. We conclude that thermal intolerance explains, at least in part, the absence of red spruce at low elevations and latitudes where temperatures of >/= 30 degrees C occur. We suggest that the thermosensitivity of this species is important with respect to global climate trends and migration patterns.

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PubMed1994

Element concentrations in the xylem sap of Picea abies (L.) Karst. seedlings extracted by various methods under different environmental conditions.

We used a Scholander pressure chamber to assess the effects of various extraction methods under different environmental conditions on element concentrations in xylem sap of 3-year-old Picea abies (L.) Karst. seedlings. Sap from excised shoots contained higher element concentrations when extracted at low than at high over-pressures. When comparing plants differing in water status, we found that a high extraction over-pressure introduced a systematic error into the data. For example, in well-watered non-transpiring plants relative to unwatered transpiring plants, potassium concentrations were 70% higher in sap extracted at 0.1 MPa over-pressure, but only 10% higher in sap extracted at 1.0 MPa over-pressure. Moreover, treatment effects depended on the time of day when the sap was extracted. Increased water flux in transpiring plants relative to non-transpiring plants resulted in reduced xylem sap element concentrations when samples were collected after 9 h of transpiration, but not after 4 to 6 h of transpiration. Drought had little effect on xylem sap element concentrations, indicating that rates of element release into xylem conduits, element depletion by growing tissues, and water flow maintained a balance that may prevent nutrient stress during short-term drought.

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PubMed1994

Effects of elevated nitrate and aluminum on the growth and nutrition of red spruce (Picea rubens) seedlings.

Acidic deposition in high-elevation forests in the Appalachian Mountains of the eastern United States has been implicated in the decline of red spruce (Picea rubens Sarg.). Elevated soil acidity may increase soil Al availability and toxicity to roots. Enhanced soil solution NO(3) (-) concentrations, resulting from precipitation inputs and enhanced soil organic matter mineralization, may exacerbate Al toxicity by increasing root Al uptake. We exposed red spruce seedlings to 350, 500, 800 or 1400 micro M NO(3) (-) and 0 or 200 micro M Al in a factorial design in sand-nutrient solution culture to test if increased NO(3) (-) concentrations enhance Al uptake and toxicity. In addition to significant reductions in seedling growth parameters resulting from Al exposure, we found significant interactions between NO(3) (-) and Al for seedling height growth rate, needle weight, shoot weight and root weight. Differences in these parameters between Al treatments became more pronounced as solution NO(3) (-) concentration increased and reflected an Al-mediated inhibition of seedling response to increasing NO(3) (-) concentration. Solution NO(3) (-) concentrations above 500 micro M induced root nitrate reductase (NR) activity, whereas shoot NR activity increased in response to NO(3) (-) up to 500 micro M and declined above that concentration. In contrast, exposure to Al depressed NR activity of roots but tended to stimulate needle NR activity. Foliar N concentrations increased in seedlings grown in cultures containing between 350 and 500 micro M NO(3) (-), with no change above 500 micro M. Increasing concentrations of NO(3) (-) depressed foliar P concentrations, with reductions being greatest in seedlings exposed to 1400 micro M NO(3) (-). Exposure to Al increased foliar Ca, K and Al concentrations, decreased foliar P concentrations, and inhibited increases in foliar Mg concentration in response to increasing NO(3) (-). The consistent interactions between NO(3) (-) and Al for growth, root NR activity and foliar Mg concentration were the result of an inhibition of seedling response to NO(3) (-) mediated by Al in solution, rather than enhanced Al toxicity resulting from growth in the presence of elevated NO(3) (-) concentrations.

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PubMedDate not supplied

Effects of elevated CO(2), nutrition and climatic warming on bud phenology in Sitka spruce (Picea sitchensis) and their impact on the risk of frost damage.

Effects of elevated CO(2), clone and plant nutrition on bud dormancy of Sitka spruce (Picea sitchensis (Bong.) Carr.) were examined. Sitka spruce seedlings were fumigated with ambient or elevated (ambient + 350 micro mol mol(-1)) concentrations of CO(2) in open-top chambers for three growing seasons. In 1991 and 1992, elevated CO(2) delayed bud burst in the spring and advanced bud set in the autumn. The effect of the open-top chamber on the thermal requirement for bud burst was greater than the effect of elevated CO(2) (50 and 30 day degrees (D(d)), respectively). In a second study, four clones of Sitka spruce taken from two provenances, at 43 and 54 degrees N, were fumigated with ambient or elevated CO(2). There was a large natural variation in the timing of bud burst and bud set among the clones. Elevated CO(2) had no effect on bud dormancy of the Skidegate a clone, but it reduced the growing season of the North Bend b clone by 20 days. In a third study, Sitka spruce seedlings growing in ambient or elevated CO(2), were supplied with one of three nutrient regimes, low (0.1 x potential), medium (0.5 x potential) or high (2.0 x potential), using a method and solution based on the Ingestad technique. Elevated CO(2) did not affect bud dormancy in the high-nutrient treatment, but it reduced the growing season of plants in the low-nutrient treatment by 22 days. Increasing plant nutrient supply lengthened the growing season, plants flushed earlier in the spring and set bud later in the autumn. The effects of elevated CO(2) plus a 0, 2 or 4 degrees C climatic warming on the timing of bud burst and the subsequent risk of frost damage were assessed using a simulation model and meteorological data from three sites, Edinburgh, Braemar and Masset. The model predicted that (i) doubling the CO(2) concentration in the absence of climatic warming, will delay the onset of bud burst at all three sites, (ii) climatic warming in ambient CO(2) will hasten bud burst and (iii) climatic warming in elevated CO(2) will hasten bud burst at Edinburgh and Braemar but to a lesser extent than climatic warming alone. At Masset, a 4 degrees C warming was required to advance the date of bud burst of seedlings in the elevated CO(2) treatment. At all three sites, elevated CO(2) and climatic warming increased the mean daily temperature on the date of bud burst, thus reducing the risk of subsequent frost damage.

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PubMed1995

Seasonal variation in photochemical activity and hardiness in clones of Norway spruce (Picea abies).

We investigated changes in photochemical activity and cold hardiness of detached needles of three clones of Picea abies (L.) Karst. by measuring variable chlorophyll fluorescence (F(v)/F(m)), before and after artificial freezing, from September to June. Photochemical activity varied considerably during the study, but only minor differences in photochemical activity among the clones were observed before freezing. Photochemical activity was high during early fall and then declined from November until April. Photochemical activity was at a minimum in April and then increased quickly to high values in May. During the period from late September to October, and also during the winter, differences in F(v)/F(m) ratios after artificial freezing to below -10 degrees C were observed among clones, indicating clonal differences in cold hardiness and hardiness development. The clone having an average height of 2.3 m after 11 years showed consistently lower cold hardiness than clones that had reached average heights of 4.0 and 5.0 m. There were also differences in the temperature requirement for bud flushing among clones.

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PubMed1995

Prediction of stem profile of Picea abies using a process-based tree growth model.

We built a simple tree growth model for Norway spruce (Picea abies (L.) Karst.) that describes the biomass and stem radial growth of one tree in a stand. Growth is controlled by an external height growth function that accounts for site quality. Crown recession is represented by an empirical function that accounts for the limitation to crown development caused by mechanical contacts with neighboring trees. The model describes biomass growth based on carbon budget (photosynthesis, respiration and senescence) and carbon partitioning between foliage, stem and root compartments. An internal regulation is introduced based on a functional balance between crown and root development. Stem annual growth is distributed along the stem by means of an empirical rule. Stem profile is the final output of the model and can be used to check the overall consistency of the model and as an aid in wood quality studies. The underlying assumptions of the model are described.

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PubMed1995

Recovery of photosynthesis in 1-year-old needles of unfertilized and fertilized Norway spruce (Picea abies (L.) Karst.) during spring.

Photosynthetic O(2) evolution and chlorophyll a fluorescence were measured in 1-year-old needles of unfertilized and fertilized trees of Norway spruce (Picea abies (L.) Karst.) during recovery of photosynthesis from winter inhibition in northern Sweden. Measurements were made under laboratory conditions at 20 degrees C. In general, the CO(2)-saturated rate of O(2) evolution was higher in needles of fertilized trees than in needles of unfertilized trees over a wide range of incident photon flux densities. Furthermore, the maximum photochemical efficiency of photosystem (PS) II, as indicated by the ratio of variable to maximum fluorescence (F(V)/F(M)) was higher in needles of fertilized trees than in needles of unfertilized trees. The largest differences in F(V)/F(M) between the two treatments occurred before the main recovery of photosynthesis from winter inhibition in late May. The rate of O(2) evolution was higher in needles of north-facing branches than in needles of south-facing branches in the middle of May. Simultaneous measurements of O(2) exchange and chlorophyll fluorescence indicated that differences in the rate of O(2) evolution between the two treatments were paralleled by differences in the rate of PS II electron transport determined by chlorophyll fluorescence. We suggest that, during recovery of photosynthesis from winter inhibition, the balance between carbon assimilation and PS II electron transport was maintained largely by adjustments in the nonphotochemical dissipation of excitation energy within PS II.

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PubMed1995

Effects of cold storage and water stress on water relations and gas exchange of white spruce (Picea glauca) seedlings.

To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis.

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PubMed1995

Effects of light availability and tree size on the architecture of assimilative surface in the canopy of Picea abies: variation in needle morphology.

Needle dimensions, needle surface area, needle dry weight per area (LWA) and needle density (ND, needle weight per volume) were measured in terminal current-year shoots in a natural canopy of variably sized Picea abies (L.) Karst. trees growing along a light gradient. Needle shape was described as a rhomboid. Needle width (D(2)) increased with increasing diffuse site factor, a(d) (relative amount of penetrating diffuse solar radiation), whereas needle thickness (D(1)) remained nearly constant, resulting in an inverse relationship between D(1)/D(2) and a(d) and an increase in the ratio of total (TLA) to projected needle surface area (PLA) with increasing a(d). Because of the variations in needle morphology with respect to light availability, the shoot parameters used in present canopy models are also expected to be light-sensitive, and studies involving shoot morphology should also consider the variability in needle geometry. Needle dimensions and total tree height were not correlated. However, LWA increase with both increasing a(d) and total tree height. When LWA was expressed as the product of ND and needle height (NH, height of the rhomboidal transverse section of a needle), LWA appeared to increase with irradiance, because of changing NH, and with total tree height, because of changing needle density.

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PubMedDate not supplied

Transport and metabolism of gibberellins in relation to flower bud differentiation in Norway spruce (Picea abies).

A mixture of tritiated and deuterated gibberellin A(4) (GA(4)) was injected into the xylem of Norway spruce (Picea abies (L.) Karst) propagules, below an elongating shoot, or applied directly on the needles of an elongating shoot. The distribution of [(2)H(2)]GA(4) and [(3)H]GA(4) in the needles, stems and buds was determined after 4, 12 and 24 h. After 4 h, most of the xylem-injected GA(4) was found in the needles, whereas after 24 h, most of the GA(4) was found in the stem, with a small portion in the lateral buds. Of the GA(4) applied to the needles, 51% of the radioactivity recovered after 24 h was found in the stem and 2% in the lateral buds. Mixtures of tritiated and deuterated GA(4) and GA(9) were injected into elongating shoots of one abundant-flowering family and one limited-flowering family, grown either under conditions inductive for flowering (hot and dry, HD) or under noninductive conditions for flowering (cool and wet, CW). Shoots of both CW- and HD-treated propagules converted [(2)H(2)]GA(9) to [(2)H(2)]GA(51), [(2)H(2)]GA(4), [(2)H(2)]GA(34) and [(2)H(2)]GA(1), whereas [(2)H(2)]GA(4) was converted to [(2)H(2)]GA(34), [(2)H(2)]GA(1) and [(2)H(2)]GA(8). In shoots of both CW-treated clones, the main metabolite of [(3)H]GA(9) was in the GA(51) region. The HD-treated propagules converted more [(3)H]GA(9) to putative GA(4) than the CW-treated propagules. The main metabolite of [(3)H]GA(4) was in the GA(34) region. Radioactive metabolites were also found in the GA(1) and GA(8) regions.

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PubMedDate not supplied

Effects of gibberellin A(4/7), root pruning and cytokinins on seed and pollen cone production in black spruce (Picea mariana).

Stem injections of 8-9-year-old black spruce (Picea mariana (Mill.) B.S.P.) trees with gibberellin A(4/7) (GA(4/7)) alone and in combination with root pruning increased both seed and pollen cone production in both 1991 and 1992. Combining GA(4/7) and root pruning produced a larger increase in reproductive bud production than either treatment alone, but the complementary effects were less during the warm dry summer in 1991 than during the wet summer in 1992. Cytokinin applications reduced the stimulatory effects of GA(4/7) and root pruning, and the degree of reduction varied with the amount and timing of application. Reduced reproductive bud production was attributed to cytokinin countering the effects of root pruning and natural drought on the GA(4/7) response.

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PubMedDate not supplied

Influences of crown size and maturation on flower production and sex expression in Picea glauca treated with gibberellin A(4/7).

We evaluated the effects of exogenous gibberellin A(4/7) (GA(4/7)) on the production of seed and pollen cones in four stock types of Picea glauca (Moench) Voss. From 1987 to 1991, a combined treatment that included GA(4/7), root pruning and heat stress was applied to 5- to 10-year-old container-grown grafts, representing over 90 clones and originating from 17- to 27-year-old ortets. Hormonal treatments were applied to pruned field-grown grafts in 1991 and 1992, and to unpruned field-grown grafts from the same set of clones in 1990, 1991 and 1992. In 1992, 26-year-old mature trees in a progeny test were treated with GA(4/7). The GA(4/7) treatment was effective in promoting seed-cone production in all four stock types, whereas it promoted pollen-cone production only in unpruned field-grown grafts and mature trees. The older and taller a tree, the less the response to the GA(4/7) treatment was influenced by the climatic conditions prevailing during the differentiation phase.

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