Jack Pine Seedlings Research Articles

Ectomycorrhizal fungi affect the physiological responses of Picea glauca and Pinus banksiana seedlings exposed to an NaCl gradient

We tested the effects of ectomycorrhizal (ECM) inoculation on greenhouse-grown white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana L.) seedlings to be used for revegetation of salt-affected tailing sands resulting from the exploitation of oil sand in northeastern Alberta, Canada. White spruce and jack pine seedlings were inoculated with three ECM fungi selected for their in vitro tolerance to excess Na+ and Cl-: Hebeloma crustuliniforme (Bull) Quel. UAMH 5247, Laccaria bicolor Maire (Orton) UAMH 8232 and a Suillus tomentosus (Kauff.) Sing., Snell and Dick isolate from a salt-affected site. The physiological responses of the seedlings to a gradient of NaCl concentration (0, 50, 100 and 200 mM) were assessed over four weeks by: (1) Na+ accumulation and allocation; (2) chlorophyll a fluorescence; (3) growth, (4) water content; and (5) organic osmolyte accumulation. Jack pine seedlings were more sensitive than white spruce seedlings to increasing Na+ and Cl- concentrations. Both species showed decreasing biomass accumulation, and increasing concentrations of organic osmotica and Na with increasing NaCl concentration. White spruce seedlings inoculated with the S. tomentosus isolate had the best growth response at all NaCl concentrations tested. Although jack pine seedlings inoculated with the L. bicolor or S. tomentosus isolate exhibited the highest growth in the 50 and 100 mM NaCl treatments, both fungi increased the photochemical stress and dehydration of their hosts in the 200 mM NaCl treatment. At the latter concentration, jack pine seedlings inoculated with H. crustuliniforme showed the greatest tolerance to salt stress. Although the different fungi altered the physiological response of the host in different ways, inoculation with salt-stress-tolerant ECM fungi increased growth and reduced the negative effects of excess NaCl. Use of controlled mycorrhization may increase survival of coniferous seedlings used for revegetation of salt-affected sites.

Gas Exchange and Growth Responses of Ectomycorrhizal Picea mariana, Picea glauca, and Pinus banksiana Seedlings to NaCl and Na2SO4

Black spruce (PICEA MARIANA), white spruce (PICEA GLAUCA), and jack pine (PINUS BANKSIANA) seedlings were inoculated with HEBELOMA CRUSTULINIFORME or LACCARIA BICOLOR and subjected to NaCl and Na (2)SO (4) treatments. The effects of ectomycorrhizas on salt uptake, growth, gas exchange, and needle necrosis varied depending on the tree and fungal species. In jack pine seedlings, ectomycorrhizal (ECM) fungi reduced shoot and root dry weights and in the ECM white spruce, there was a small increase in dry weights. Sodium chloride treatment reduced net photosynthesis and transpiration rates in the three studied tree species. However, NaCl-treated black spruce and jack pine colonized by H. CRUSTULINIFORME maintained relatively high photosynthetic and transpiration rates and needle necrosis of NaCl-treated black spruce seedlings was reduced by the ECM fungi. Higher concentrations of Na (+) were found in shoots compared with roots of the three examined conifer species. ECM fungi reduced the concentrations of Na (+) mainly in the shoots and this reduction was greater in plants treated with NaCl compared with Na (2)SO (4). Shoots contained generally higher concentrations of Cl (-) compared with roots. In the NaCl-treated black spruce and white spruce, both ECM species significantly reduced Cl (-) concentrations. Our results point to overall greater phytotoxicity of NaCl compared with Na (2)SO (4) and support our earlier findings which demonstrated beneficial effects of ECM fungi for woody plants exposed to NaCl stress.

A Species-Specific PCR Assay for Detection of Diplodia pinea and D. scrobiculata in Dead Red and Jack Pines with Collar Rot Symptoms.

A polymerase chain reaction (PCR)-based assay was developed for the specific detection of the fungal pathogens Diplodia pinea and D. scrobiculata from pine host tissues. Variation among mitochondrial small subunit ribosome gene (mt SSU rDNA) sequences of Botryosphaeria species and related anamorphic fungi was exploited to design primer pairs. Forward primer DpF and forward primer DsF, each when used with the nonspecific reverse primer BotR, amplified DNA of D. pinea or D. scrobiculata, respectively. Specificity was confirmed using multiple isolates of each of these two species and those of closely related fungi including Botryosphaeria obtusa. The detection limits for DNA of each pathogen in red and jack pine bark were 50 to 100 pg μl-1 and 1 pg μl-1 in red and jack pine wood. The assay was tested using naturally occurring red and jack pine seedlings and saplings exhibiting symptoms of Diplodia collar rot. Samples from lower stems/root collars of 10 dead trees of each species from each of three sites at each of two locations were tested. Results were positive for D. pinea or D. scrobiculata for the large majorities of symptomatic bark and wood samples from both locations. For positive samples, however, there were effects of location and host species on detection of D. pinea (more frequent on red pine) and D. scrobiculata (more frequent on jack pine) (P < 0.01 in both cases). These results indicate that these new primers are potentially useful for studies in areas or hosts in which both pathogens may be present.

Growth response and water relations of 3-year-old planted black spruce and jack pine seedlings in site prepared lichen woodlands

Black spruce-lichen woodlands are low tree density stands within the closed crown, North American boreal forest that represent a diverging post-fire type of black spruce forest. As natural densification of lichen woodlands has never been observed, afforestation remains the only way of shifting these stands to closed canopy stands. The objective of the study was to evaluate site preparation effects on growth and water relations of black spruce ( Picea mariana (Mill.) B.S.P.) and jack pine ( Pinus banksiana Lamb.) seedlings in black spruce-lichen woodlands (LW), compared to managed black spruce-feathermoss stands (BSFM). Site preparation treatments in LW were no preparation (LWno), patch scarification (LWps), and disk scarification (LWds). The operationally managed BSFM stands stood for the control. Results from the third growing season indicate that soil water availability in intact or lightly prepared patch scarified LW is a limiting variable for seedling growth for both black spruce and jack pine seedlings. However, once LW are prepared with disk scarification, this planting check factor is significantly reduced, to the point of being equal to BSFM in terms of water availability and seedling water relations. The significant seedling growth difference, in favor of BSFM, might be a consequence of the lower level of pre-plantation disturbance in LW, compared to BSFM. Our results also suggest that jack pine, through higher water stress tolerance, could constitute a wise silvicultural choice over black spruce, especially with LW established on coarse drought-prone material.

Effects of soil temperature and elevated atmospheric CO2 concentration on gas exchange, in vivo carboxylation and chlorophyll fluorescence in jack pine and white birch seedlings

One-year-old jack pine (Pinus banksiana Lamb.) and current-year white birch (Betula papyrifera Marsh.) seedlings were grown in ambient (360 ppm) or twice ambient (720 ppm) atmospheric CO2 concentration ([CO2]) and at three soil temperatures (Tsoil = 7, 17 and 27 degrees C initially, increased to 10, 20 and 30 degrees C two months later, respectively) in a greenhouse for 4 months. In situ foliar gas exchange, in vivo carboxylation characteristics and chlorophyll fluorescence were measured after 2.5 and 4 months of treatment. Low Tsoil suppressed net photosynthetic rate (Pn), stomatal conductance (g(s)) and transpiration rate (E) in jack pine in both CO2 treatments and g(s) and E in white birch in ambient [CO2], but enhanced instantaneous water-use efficiency (IWUE) in both species after 2.5 months of treatment. Treatment effects on g(s) and E remained significant throughout the 4-month study. Low Tsoil reduced maximal carboxylation rate (Vcmax) and PAR-saturated electron transport rate (Jmax) in jack pine in elevated [CO2] after 2.5 months of treatment, but not after 4 months of treatment. Low Tsoil increased actual photochemical efficiency of photosystem II (PSII) in the light (DeltaF/Fm') in jack pine, but decreased DeltaF/Fm' in white birch after 4 months of treatment. In response to low Tsoil, photosynthetic linear electron transport to carboxylation (Jc) decreased in jack pine after 2.5 months and in white birch after 4 months of treatment. Low Tsoil increased the ratio of the photosynthetic linear electron transport to oxygenation (Jo) to the total photosynthetic linear electron transport rate through PSII (Jo/J(T)) in both species after 2.5 months of treatment, but the effects became statistically insignificant in white birch after 4 months of treatment. High Tsoil decreased foliar N concentration in white birch. Elevated [CO2] increased Pn, IWUE and Jc but decreased Jo/J(T) in both species at both measurement times except Jc in white birch after 2.5 months of treatment. Elevated [CO2] also decreased g(s) and E in white birch at high Tsoil, Vcmax in both species and triose phosphate utilization in white birch at low Tsoil after 4 months of treatment, and DeltaF/Fm' in white birch after 2.5 months of treatment. Elevated [CO2] also increased foliar N concentration in both species. Low Tsoil caused no permanent damage to PSII in either species, but jack pine responded and acclimated to low Tsoil more quickly than white birch. Photosynthetic down-regulation and a decrease in photosynthetic electron transport to photorespiration occurred in both species in response to elevated [CO2].

The effect of two ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and of Bacillus subtilis on Fusarium damping-off in jack pine seedlings

Two species of ectomycorrhizal fungi, Paxillus involutus and Suillus tomentosus, and a bacterial strain of Bacillus subtilis, were tested against Fusarium moniliforme, the causal agent of damping-off in jack pine (Pinus banksiana) seedlings. Both P. involutus and B. subtilis inhibited in vitro growth of F moniliforme. The culture filtrates of P. involutus and B. subtilis were toxic to F moniliforme, but chlamydospore formation of F moniliforme was observed. Greater jack pine seedling survival was observed when co-inoculated with P. involutus and B. subtilis than with F moniliforme alone. S. tomentosus neither inhibited in vitro growth of F moniliforme nor increased survival of jack pine seedlings against F moniliforme. F moniliforme reduced ectomycorrhiza formation on jack pine seedlings by P. involutus and S. tomentosus. The number of colony forming units of F moniliforme was significantly reduced when seedlings were inoculated with P. involutus and B. subtilis alone or in combination. S. tomentosus, on the other hand, did not reduce the number of colony forming units of F moniliforme. The suppression of F moniliforme growth by P. involutus and B. subtilis involved production of antifungal compounds.

Resistance of Pinus banksiana to the European race of Gremmeniella abietina

In the early 1980s, more than 90% of mortality caused by Gremmeniella abietina, European race, was recorded in red pine (Pinus resinosa) plantations 200 km northwest of Montreal, Quebec, Canada. Surrounding jack pines (Pinus banksiana) did not appear to be affected. Consequently, foresters began to plant the affected areas with jack pine seedlings. In 1988, plots of 100 jack pines were established in three of the four selected plantations. As reference, red pine seedlings were planted in 1989 under similar conditions in the fourth plantation. Observations were carried out annually from 1989 to 1992. Mortality of red pine seedlings reached 70% in 1992 while all jack pines on the three experimental sites were free of the disease except for a tip blight, a distinctive feature allowing race identification in the field. The North American race symptoms were present at a very low incidence, but began to increase on site I in 1992. More than 10 years after planting, the jack pine trees still show resistance to the European race of G. abietina while all the red pines died.

Black spruce and jack pine dynamics simulated under varying fire cycles in the northern boreal forest of Quebec, Canada

The postfire regeneration dynamics of black spruce and jack pine were documented by a study of three successive cohorts (woody debris, snags, seedlings) within a large area burnt in 1989. The objectives of this study were (i) to describe how fire interval can influence the abundance of regenerating black spruce and jack pine and (ii) to model the future abundance trends of these two species for fire cycles of different lengths. The transition probabilities after fire were calculated for mixed stands of black spruce and jack pine for fire intervals of 47 and 67 years in well-drained sites and for fire intervals varying between 92 and 270 years in poorly drained sites. These probabilities were incorporated into a model of regeneration dynamics that took into account the drainage type, the regeneration potential, and the natural mortality rate of both species. After the 1989 fire, jack pine seedlings made up 55%–82% of the regeneration in well-drained sites and 11%–40% in poorly drained sites. Model simulations show that fire intervals &lt;60 years lead to the local extinction of black spruce, and those &gt;220 years lead to that of jack pine. The simulation results also suggest that jack pine could expand its populations under a fire cycle of 50 years or after short fire intervals during longer fire cycles. Thus, in the short term and medium term (i.e., ca. &lt;100 years), the length of the interval between two consecutive fires is a better predictor of the abundance, extinction, or local expansion of black spruce and jack pine than the fire cycle.

Influence of seedbed, light environment, and elevated night temperature on growth and carbon allocation in pitch pine ( Pinus rigida) and jack pine ( Pinus banksiana) seedlings

Jack pine ( Pinus banksiana Lamb.) and pitch pine ( Pinus rigida Mill.) are two autecologically similar species that occupy generally disjunct ranges in eastern North America. Jack pine is boreal in distribution, while pitch pine occurs at temperate latitudes. The two species co-occur in a small number of stands along a ‘tension-zone’ that traverses central Maine. These populations provide an opportunity for studying differences between boreal and temperate species in their adaptation to climatic factors. As seedling establishment and early growth are key life-stages governing tree distribution, we experimentally evaluated the influence of seedbed light environment and substrate on the success and early growth of these species. Under similar environments, first-year jack pine seedlings allocated relatively more biomass to roots and pitch pine more to foliage. This might provide pitch pine with an adaptive advantage when soil moisture was not limiting and an advantage to jack pine if substantial moisture stress occurred. Complex ontogenetic shifts in these allocation patterns occurred over second and third years of growth, which resulted in an equalization of interspecific differences in shoot–root ratios by the end of the third growing season. Night temperatures of 4–5 °C above ambient reduced growth of jack pine seedlings, while that of pitch pine was unaffected. However, foliar respiration and respiratory response to temperature were not significantly different between species and did not explain observed differences in temperature response.

Phenylalanine ammonia‐lyase‐induced freezing tolerance in jack pine (Pinus banksiana) seedlings treated with low, ambient levels of ultraviolet‐B radiation

Phenylalanine ammonia‐lyase (PAL) induction in UVB‐exposed plants leads to an increased synthesis of UV‐absorbing phenols. As phenols, including anthocycanins, are linked to many protective mechanisms in plants, we tested the hypothesis that UVB‐induced phenol accumulation, mediated by PAL, may confer freezing tolerance in jack pine (Pinus banksiana Lamb) seedlings. The hypothesis was tested by applying UVB in the presence and absence of the PAL‐inhibitor, 2‐aminoindan‐2‐phosphonic acid (AIP). Jack pine seedlings were grown for 3 weeks with and without 10 µM aqueous AIP. Each treatment was then divided into two groups. One group received near‐ambient UVB (5.5 kJ m−2 day−1of biologically effective radiation) for up to 30 h. A second, control group of seedlings received no UVB. Anthocyanin concentration declined by &gt; 99% in PAL‐inhibited seedlings and other methanol‐extractable UV‐absorbing phenols declined by &gt; 48%, relative to the controls. A 20‐h exposure to UVB increased seedling freezing (−15°C) tolerance in the absence of the PAL‐inhibitor, as shown by a 30% reduction in membrane injury, determined by electrolyte leakage measurements. In PAL‐inhibited seedlings, by contrast, the same UVB pre‐treatment increased freezing injury by 48%. A longer (30 h) UVB exposure was damaging to both AIP‐treated and untreated seedlings. Root feeding with 10 µM AIP during a 3‐week exposure of older (6‐month‐old) seedlings similarly reduced phenol accumulation in UVB‐exposed seedlings. The decline in phenol production in PAL‐inhibited seedlings correlated with increased freezing injury. These results suggest a role for ambient UVB in seedling frost hardiness, mediated by a PAL‐induced production of phenolic compounds.

Régénération artificielle des pessières noires à éricacées : effets du scarifiage, de la fertilisation et du type de plants après 10 ans

Site invasion by ericaceous shrubs after perturbation, either natural or human, is a major concern on some sites of the boreal forest of Québec. A dense cover of ericaceous shrubs often induces a conifer "growth check," which can last several decades. An interaction study was initiated in 1991 with the general objective of developing silvicultural strategies to ensure plantation success on such sites. Black spruce, jack pine, and tamarack seedlings were planted. Stock type, scarification, and fertilization treatments were organised in a randomized block split plot design. We measured seedling total height periodically over a ten-year period and assessed basal area and survival ten years after plantation. Most responses to treatments were additive. Results indicated that mechanical soil scarification is of major importance to ensure seedling growth, both in height and basal area, on spruce-ericaceous shrub sites of northeastern Québec. Scarification allowed a better expression of the site index, implying a sustainable impact on microsite characteristics that is greater than short-term effects on mineralization and nutrient availability. Fertilization positively influenced seedling growth, but less than soil scarification. Species choice had a strong impact on site productivity. Over a ten-year period, stock types only had a minor influence on plantation success, when compared to scarification or fertilization effects. Key words: Kalmia angustifolia, ericaceous shrubs, survival, growth, regeneration, black spruce, jack pine, tamarack

Boron and water uptake in jack pine ( Pinus banksiana) seedlings

We studied the effects of 0.5, 1 and 2 mM boron (B) on growth, water and nutrient uptake in 6-month-old jack pine ( Pinus banksiana) seedlings. After 6 weeks of treatment, B did not significantly affect survival and the measured growth parameters in jack pine. However, B-treated seedlings exhibited needle tip necrosis that progressed toward the bases of the needles in high concentration treatments. The visible needle injury was accompanied by an increase in electrolyte leakage from the needles and B accumulation in needles. The needles of plants treated with 2 mM B contained three-fold higher concentration of B than with the roots. In plants treated with B for four 10 and 6 weeks, stomatal conductance was reduced with a concomitant reduction in a steady-state root water flow. However, tissue concentrations of essential elements including K, P, Ca, Mg, and S were not altered by the B treatments. Therefore, water transport did not appear to affect uptake and distribution of mineral nutrients in jack pine and the observed needle necrosis and electrolyte leakage could be explained by B accumulation in the needles. Although photosynthetic pigments and the measured growth parameters were not altered by the 6-week B treatments, long-term growth effects should be anticipated due to effect of B on water relations.

Adhesives for seed placement during artificial inoculation of Pinus banksiana seedlings with the dwarf mistletoe Arceuthobium americanum

Lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is a serious pest of jack pine (Pinus banksiana Lamb.). Research investigating factors such as host resistance, influence of host nutrition on infection rates, and effect of temperature and humidity on the life cycle of the pathogen is limited by our ability to consistently infect the host through artificial means. A greenhouse experiment utilizing a completely randomized design with four replicates was conducted to test the effectiveness of three chemical compounds and the natural viscin of the dwarf mistletoe seed to act as adhesives during artificial inoculation of jack pine seedlings. Synthetic adhesives used were anhydrous lanolin (LAN), hydroxypropylcellulose (HPC), and polyvinyl acetate (PVA). The percentage of infected seedlings was significantly higher with HPC compared with that of PVA, LAN, and the seed's viscin. HPC, as the superior adhesive, and the techniques described should allow consistent production of seedlings infected with dwarf mistletoe for research, regardless of the dwarf mistletoe species involved. Problems encountered during the testing of the adhesives are discussed in relation to the nature of the adhesives and their application.Key words: anhydrous lanolin, hydroxypropylcellulose, polyvinyl acetate, viscin.

Hydraulic adjustment in jack pine and black spruce seedlings under controlled cycles of dehydration and rehydration.

Drought adjustments were compared in black spruce (Picea mariana[Mill] B.S.P), and jack pine (Pinus banksiana[Lamb.]) by subjecting seedlings to five cycles of dehydration and rehydration. A computer-controlled root misting chamber system, supplied low (-1.5 MPa), moderate (-2.0 MPa), and severe (-2.5 MPa) dehydration, respectively, in cycles 1, 3 and 5. Although cell water relations failed to adjust to chronic dehydration, there was limited osmotic adjustment in black spruce (cycle 3), and water was re-allocated from the apoplast to the symplast in jack pine (cycles 1 and 3). Dehydration postponement was more important than dehydration tolerance. Jack pine was better able to postpone dehydration than black spruce. Specific conductivity, the hydraulic conductivity per unit stem cross-sectional area, was lower in jack pine and slower to decline during chronic dehydration. When specific conductivity was corrected for the greater leaf area in black spruce, the leaf-specific conductivity did not differ in the two species. There was no increase in needle leakage in jack pine and stomata in jack pine seedlings reopened fully after rehydration. Black spruce was more of a 'water spender', and less water stress (-2.0 MPa, cycle 3) was required to lower specific conductivity, compared to jack pine (-2.5 MPa, cycle 5). Leakage from needle membranes increased in black spruce, and stomata failed to reopen after rewatering (cycles 3 and 5). A greater needle area, smaller root system, and a higher specific conductivity lowered the water stress threshold for cavitation in black spruce, which is confined to moister sites in the boreal forest. Jack pine had a larger root system, smaller needle area and lower specific conductivity than black spruce. Because of these static features, jack pine is more drought tolerant and it is often found on sites that are too hot and dry for black spruce.

Hypoxia affects root sodium and chloride concentrations and alters water conductance in salt-treated jack pine (Pinus banksiana) seedlings

The effects of NaCl were studied in 6-month-old jack pine (Pinus banksiana Lamb.) seedlings growing in solution culture under hypoxic (approximately 2 mg l−1 O2) and well-aerated (approximately 8 mg l−1 O2) conditions. The results showed that hypoxia led to further reduction of stomatal conductance (g s) in plants treated with 45 mM NaCl. This effect was likely due to a reduction in root hydraulic conductance by both stresses. When applied individually or together, neither 45 mM NaCl nor hypoxia affected cell membrane integrity of needles as measured by tissue electrolyte leakage. Hypoxia did not alter shoot Na+ and Cl− concentrations in NaCl-treated plants. However, root Na+ concentrations were lower in NaCl-treated hypoxic plants, suggesting that hypoxia affected the ability of roots to store Na+. Hypoxia also induced root electrolyte leakage from NaCl-treated and control plants. The higher root Cl− concentrations compared with Na+ and the positive correlation between root Cl− concentrations and electrolyte leakage suggest that Cl− played a major role in salt injury observed in jack pine seedlings. Roots of well-aerated plants treated for 1 week with NaCl contained almost two-fold higher concentration of total non-structural carbohydrates compared with plants from other experimental treatments and these concentrations decreased in subsequent weeks. We suggest that under prolonged hypoxic conditions, roots lose the ability to prevent Cl− uptake resulting in the increase in root Cl− concentration, which has damaging effects on root cell membranes.

Interspecific competition for nitrogen between early successional species and planted white spruce and jack pine seedlings

Relatively little is known about belowground competition for nitrogen (N) between boreal forest species. The objective of this study was to compare the relative competitiveness of three early successional boreal forest species, trembling aspen (Populus tremuloides Michx.), fireweed (Epilobium angustifolium L.), and calamagrostis (Calamagrostis canadensis (Michx.) Beauv.), on 15N uptake and the growth response by containerized white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb.) seedlings. Three densities (0, 2, and 6 plants/pot) of each competitor species were interplanted with individual seedlings in pots with 15N-labelled fertilizer and grown for 3 months. The conifer seedlings had the greatest fertilizer 15N uptake (129.5 and 82.3 µg/m2 root for white spruce and jack pine, respectively) when grown in monoculture and the lowest uptake when interplanted with six competitor plants (9.2 and 8.6 µg/m2 root for white spruce and jack pine, respectively). Whether grown in monoculture or with conifer seedlings, calamagrostis took up the greatest amount of fertilizer 15N. Vegetation management practices that reduce the establishment of this grass species in the field should benefit N uptake and growth of outplanted white spruce and jack pine seedlings.

Low growth temperature inhibition of photosynthesis in cotyledons of jack pine seedlings (Pinus banksiana) is due to impaired chloroplast development

Cotyledons of jack pine seedlings (Pinus banksiana Lamb.) grown from seeds were expanded at low temperature (5°C), and total Chl content per unit area of cotyledons in these seedlings was only 57% of that observed for cotyledons on 20°C-grown controls. Chl a/b ratio of 5°C-grown jack pine was about 20% lower (2.3 ± 0.1) than 20°C controls (2.8 ± 0.3). Separation of Chl-protein complexes and SDS-PAGE indicated a significant reduction in the major Chl a containing complex of PSI (CP1) and PSII (CPa) relative to LHCII1in 5°C compared to 20°C-grown seedlings. In addition, LHCII1/LHCII3ratio increased from 3.8 in control (20°C) to 5.5 in 5°C-grown cotyledons. Ultrastructurally, 5°C-grown cotyledons had chloroplasts with swollen thylakoids as well as etiochloroplasts with distinct prolamellar bodies. Based on CO2-saturated O2evolution and in vivo Chl a fluorescence, cotyledons of 5°C jack pine exhibited an apparent photosynthetic efficiency that was 40% lower than 20°C controls. Seedlings grown at 5°C were photoinhibited more rapidly at 5°C and 1200 µmol·m–2·s–1than controls grown at 20°C, although the final extent of photoinhibition was similar. Exposure to high light at 5°C stimulated the xanthophyll cycle in cotyledons of both controls and 5°C-grown seedlings. In contrast to winter cereals, we conclude that growth of jack pine at 5°C impairs normal chloroplast biogenesis, which leads to an inhibition of photosynthetic efficiency.Key words: chloroplast, growth, temperature, photosynthesis, photoinhibition, Pinus banksiana Lamb., ultrastructure.

Contrasting modes of survival by jack and pitch pine at a common range limit

Freezing tolerance, reproductive development, and seed germination of jack pine (Pinus banksiana Lamb.) and pitch pine (Pinus rigida Mill.) were compared in a small sympatric population in Acadia National Park in Maine, at the southern range limit of the former and the northern limit of the latter. Freezing tolerances of vegetative shoots and roots were similar for both species. Both species flower prolifically, and there was no evidence of differences in either pollen viability, cone survival, or proportion of viable seed (65–70% of the total). Regeneration success (established seedlings ranging from 1 to 13 years old) was similar overall for both species, but success by species varied greatly in some years. Jack pine regeneration was significantly associated with thinner soils, while pitch pine regeneration was associated with thicker soils in hollows. Jack pine seed germinated significantly faster than pitch pine seed, especially when day–night temperature was reduced. Pitch pine seedlings always exhibited a significantly higher shoot/root ratio than those of jack pine. The most northerly provenances of jack pine germinated significantly faster than those from the most southerly provenances. Jack pine also germinated at a significantly higher percentage than pitch pine in exposed granite sand. Thus relatively cool, dry conditions may favor establishment of jack pine seedlings, while pitch pine establishment may be favored in warmer, wetter conditions.

Anthocyanins of jack pine (Pinus banksiana) seedlings

Purpling of the needles of jack pine seedlings in forest tree nurseries in the autumn is a result of the production of at least five anthocyanin pigments: cyanidin 3-O-glucoside (~80%), delphinidin 3-O-glucoside (~8%), peonidin 3-O-glucoside (~8%), petunidin 3-O-glucoside (~3%) and malvidin 3-O-glucoside (trace). The twigs subtending the needles also produce a similar range of pigments. The entire spectrum of pigments is produced from the time of the first exposure to freezing temperatures. Proanthocyanidins are a prominent feature of the needle phenolics and the question of their possible involvement in the purpling phenomenon following exposure to sub-zero temperatures is raised. The red colour of the hypocotyl of the newly germinated seedling is also a result of a similar mixture of pigments.Key words: Pinus banksiana, Pinaceae, jack pine seedlings, anthocyanin pigmentation, hypocotyl, proanthocyanidins.

Growth and elemental composition of jack pine (Pinus banksiana) seedlings treated with sodium chloride and sodium sulfate

Mining activities in the boreal regions can increase levels of Na+, Cl– and SO4 2– in the forest soil. In the present study, we compared the effects of NaCl and Na2SO4 on the nutrient status of jack pine (Pinus banksiana). Germinated seedlings were grown in sand culture for 28 weeks before adding salts over a period of 3 days to treatment concentrations of 60 mM NaCl and 60 mM Na2SO4, which were maintained for 10 weeks. Salt treatments decreased shoot dry weights and shoot elongation rates. Growth and injury of seedlings were more affected by NaCl than equimolar Na2SO4. Plants treated with NaCl exhibited a delay in flushing of the terminal buds, reduced carotenoid content, extensive needle necrosis, and elevated levels of K, Mg, Mn, N and P in the shoot. Treatment with Na2SO4 resulted in reduced shoot Ca and K concentrations, while those of N and P increased. Necrosis was correlated with tissue Na only in NaCl-treated plants, and no relationship was found between growth or necrosis, and tissue levels of Cl or nutritional elements. We conclude that the greater toxicity of NaCl in jack pine is not due to nutrient deficiency.