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PubMed2003

Ecophysiology of seedlings of three Mediterranean pine species in contrasting light regimes.

Seasonal dynamics of net photosynthesis (Anet) in 2-year-old seedlings of Pinus brutia Ten., Pinus pinea L. and Pinus pinaster Ait. were investigated. Seedlings were grown in the field in two light regimes: sun (ambient light) and shade (25% of photosynthetically active radiation (PAR)). Repeated measures analyses over a 12-month period showed that Anet varied significantly among species and from season to season. Maximum Anet in sun-acclimated seedlings was low in winter (yet remained positive) and peaked during summer. Maximum Anet was observed in June in P. pinea (12 micromol m-2 s-1), July in P. pinaster (23 micromol m-2 s-1) and August in P. brutia (20 micromol m-2 s-1). Photosynthetic light response curves saturated at a PAR of 200-300 micromol m-2 s-1 in winter and in shade-acclimated seedlings in summer. Net photosynthesis in sun-acclimated seedlings did not saturate at PAR up to 1900 micromol m-2 s-1 in P. brutia and P. pinaster. Minimum air temperature of the preceding night was apparently one of the main factors controlling Anet during the day. In shade-acclimated seedlings, photosynthetic rates were reduced by 50% in P. brutia and P. pinaster and by 20% in P. pinea compared with those in sun-acclimated seedlings. Stomatal conductance was generally lower in shaded seedlings than in seedlings grown in the sun, except on days with a high vapor pressure deficit. Total chlorophyll concentration per unit leaf area, specific leaf area (SLA) and height significantly increased in P. pinea in response to shade, but not in P. pinaster or P. brutia. In response to shade, P. brutia showed a significant increase in total chlorophyll concentration but not SLA. Photosynthetic and growth data indicate that P. pinaster and P. brutia are more light-demanding than P. pinea.

Chlorophyll↗

PubMed2005

Interacting influence of light and size on aboveground biomass distribution in sub-boreal conifer saplings with contrasting shade tolerance.

Plant size often influences shade tolerance but relatively few studies have considered the functional response of taller plants to contrasting light environments. Several boreal and sub-boreal Abies, Picea and Pinus species were studied along a light (0-90% full sunlight) and size (30-400-cm high) gradient to examine the interactive influence of tree size and light availability on aboveground biomass distribution. Sampling was conducted in two regions of Canada: (A) British Columbia, for Abies lasiocarpa (Hook.) Nutt., the Picea glauca (Moench.) Voss x P. engelmannii Parry ex. Engelm. complex and Pinus contorta Dougl. var. latifolia Engelm.; and (B) Quebec, for Abies balsamea (L.) Mill., Picea glauca (Moench. Voss) and Pinus banksiana (Lamb.). All biomass distribution traits investigated varied with size, and most showed a significant interaction with both size and light, which resulted in increasing divergences among light classes as size increased. For example, the proportion of needle mass decreased as size increased but the rate of decrease was much greater in saplings growing at below 10% full sunlight. Needle area ratio (total needle area:aboveground mass) followed a similar pattern, but decreased more rapidly with increasing tree size for small trees up to 1 m tall. The proportion of needle biomass (needle mass ratio) was always lower in taller trees (i.e., > 1 m tall) than in small trees (< 1 m tall) and increasingly so at the lowest solar irradiances (0-10% full sunlight). Thus, extrapolating the functional response to light from small seedling to taller individuals is not always appropriate.

Abies↗

PubMed2006

Hydraulic design of pine needles: one-dimensional optimization for single-vein leaves.

Single-vein leaves have the simplest hydraulic design possible, yet even this linear water delivery system can be modulated to improve physiological performance. We determined the optimal distribution of transport capacity that minimizes pressure drop per given investment in xylem permeability along the needle for a given length without a change in total water delivery, or maximizes needle length for a given pressure difference between petiole and needle tip. This theory was tested by comparative analysis of the hydraulic design of three pine species that differ in the length of their needles [Pinus palustris (Engl.) Miller, approximately 50 cm; Pinus ponderosa Lawson & Lawson, approximately 20 cm and Pinus rigida Miller, approximately 5 cm]. In all three species, the distribution of hydraulic permeability was similar to that predicted by the optimum solution. The needles of P. palustris showed an almost perfect match between predicted and actual hydraulic optimum solution, providing evidence that vein design is a significant factor in the hydraulic design of pine leaves.

Pinus↗

PubMed2002

[Photosynthetic characteristics of three tree species seedlings in Changbai Mountain under different CO2 concentrations].

The photosynthetic characteristics of three-year-old seedlings of coniferous Pinus koraiensis and Pinus sylvestriformis and broadleaf Fraxinus mandshurica in open-top chambers in Changbai Mountain were studied. Seedlings were planted at four different conditions respectively:elevated CO2 concentration(700 and 500 mumol.mol-1) and ambient CO2 concentration (control chamber and in open field). After treating of two growing seasons in the first two years, seedlings were continuously grown under different CO2 concentration for another eight weeks. The results indicated that the photosynthetic capacity of three species was enhanced under high CO2 concentration in the first two growing seasons. The maximum net photosynthetic rates and light response parameters of different tree species were different at the same CO2 concentration. No photosynthetic acclimation was observed in the third growing season except Pinus sylvestriformis seedlings grown under 500 mumol.mol-1 CO2. The increase or decrease of net photosynthetic rates and light response parameters were related to the time of CO2 treatment. Elevated CO2 concentration could alter the ability of utilizing strong light and low light of seedlings.

Carbon Dioxide↗

PubMed2001

Damping-off in conifer seedling nurseries in Noshahr and Kelardasht.

To study the damping-off of conifer seedlings, we have collected samples from the roots of conifer seedlings (Pinus nigra, Picea excelsa, Abieces spp, Cupressus arizonica, Cupressus sempervirens) from nurseries in the south of Iran (Noshahr and Kelardasht). After disinfecting the samples, we have used standard media like PDA, MA and CLA. The following fungi were identified: Fusarium solani, Fusarium oxysporum, Fusarium sambucinum, Clamydosporium, Rhizoctonia solani, Cylindrocarpon spp., Alternaria spp, Macrophomina phaseoli. Amongst the above mentioned fungi, Fusarium spp. were the commonest ones. Pathogenecity tests of Fusarium spp. and Rhizoctonia solani on seedlings were done. Isolated fungal colonies were purified using single mycelium and single spore methods. Fungal isolates were identified after subculturing on PDA and CLA media by Nelson method. These isolates were Fusarium solani, F. oxysporium, F. sambucinum and F. clamydosporum. Other fungal isolates were Rhizoctonia spp. In order to determine the infectivity of Fusarium on their hosts, seeds of Pinus nigra, Cupressus arizonica and Cupressus sempervirens var. horizontalis were cultured in four repetitions each containing 2 seedlings. After a seasonal growth, seedlings were inoculated with a suspension of Fusarium spores (4.5 +/- 0.3 x 1016 spore/ml). Infection of P. nigra, Cupressus arizonica and Cupressus sempervirens var. horizontalis with F. solani and Pinus nigra and Cupressus semperivirens var. horizontalis with F. oxysporum was high whereas that of Cupressus arizonica with F. sambucinum, F. mondiforme and F. clamydosporum was moderate.

Abies↗

PubMed2005

[Landscape ecological evaluation of Fenglin Nature Reverse: quantification and interpretation].

Fenglin National Class Nature Reserve is the largest well-saved virginal Korean pine (Pinus koraiensis) forest area and a precious species gene bank in China. In this study, the indexes diversity, naturalness, representativity, rarity, area suitability, stability, and anthropogenic interference were selected to establish a ranking ecological evaluation system to estimate the ecological condition of the Reserve. The value of each index was determined by the evaluation system, and the weight percentage was decided by Analytical Hierarchy Process (AHP). In the Reserve, there were 568 higher plant species belonging to 113 families and 220 higher animal species, with score 3 of species diversity. The zonal "climax" vegetation type broad-leaved Korean pine forest and the intrazonal community type spruce-fir forest constituted the principal part of the Reserve forest, which was the epitome of the virgin broad-leaved Korean pine forest in Lesser Xing'an Mountains, with representativity score 3. During the past 20-30 years, the natural habitat in the Reserve was quite good, and secondary succession was obtained effective control with few natural or anthropogenic disturbance, with score 4 of naturalness and anthropogenic interference. There were a lot of ancient species of the tertiary period, such as Pinus koraiensis, Fraxinus mandsurica, Juglans mandshurica, Pellodendron amurense, Tilia amurensis and Acer mono, and Pinus koraiensis was listed as one of severe danger species by the FAO of UN, with rarity score 4. The Reserve covered an area of 18165 hm2, with an enough size to maintain the structure and function of the ecosystem. Accordingly, its area suitability score was 4. Broad-leaved Korean pine forest was the most typical and stable vegetation type in the Reserve, and thus, its stability score was 4. Finally, the composite evaluation index (CEI) was figured out as 0.87, showing that the ecological quality of the Reserve was very good, and the protection value was quite high. In conclusion, the present area, structure, and management of the Reserve could satisfy the requirement of sustainable development.

Biodiversity↗

PubMedDate not supplied

Electrophoretic analysis of coniferyl alcohol oxidase and related laccases.

Gradient gel electrophoretic methods enabled a distinction to be made between coniferyl alcohol oxidase (CAO) of lignifying cell walls and a pI approximately 9 pine "laccase" recently implicated in lignification (Science 1993 260, 672). Following treatment of a partially purified protein mixture from developing xylem of Pinus strobus with 2-[N-morpholine]ethanesulfonic acid (MES) buffer, isoelectric focusing and sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicated that CAO had been selectively precipitated by MES and thereby purified to electrophoretic homogeneity. Purified CAO was determined to be a cell-wall-bound glycoprotein (38% glycan), M(r) 107,500, pI 7.6, pH and temperature optima 6.3 and 30 degrees C, respectively. By graphite-furnace atomic-absorption analysis, CAO contained one copper atom per protein molecule. Proteins obtained from lignifying cambial derivatives of conifers (family Pinaceae) and from Rhus typhina bark were compared with CAO and the pI approximately 9 pine "laccase" following electrophoresis and Western blotting. For Abies balsamea, Larix laricina, Picea rubens, Pinus banksiana, Pinus taeda, and R. typhina, the isoelectric points of oxidatively active bands were identical to those of purified CAO. In addition, for all species only the pI 7.6 band was immunoreactive with antibodies against periodate-deglycosylated CAO.

Alcohol Oxidoreductases↗

PubMed1993

The phylogenetic position of Taxaceae based on 18S rRNA sequences.

The evolutionary position of the yew family, Taxaceae, has been very controversial. Some plant taxonomists strongly advocate excluding Taxaceae from the conifer order and raising its taxonomic status to a new order or even class because of its absence of seed cones, contrary to the case in the majority of conifers. However, other authors believe that the Taxaceae are not fundamentally different from the rest of the conifers except in that they possess the most reduced solitary-ovule cones. To resolve the controversy, we have sequenced the 18S rRNA genes from representative gymnosperms: Taxus mairei (Taxaceae), Podocarpus nakaii (Podocarpaceae), Pinus luchuensis (Pinaceae), and Ginkgo biloba (Ginkgoales). Our phylogenetic analysis of the new sequence data with the published 18S rRNA sequence of Zamia pumila (a.cycad) as an outgroup strongly indicates that Taxus, Pinus, and Podocarpus form a monophyletic group with the exclusion of Ginkgo and that Taxus is more closely related to Pinus than to Podocarpus. Therefore, Taxaceae should be classified as a family of Coniferales. Our finding that Taxaceae, Pinaceae, and Podocarpaceae form a clade contradicts both the view that the uniovulate seed of Taxaceae is a primitive character and the view that the Taxaceae are descendants of the Podocarpaceae. Rather, the uniovulate seed of Taxaceae and that of some species of Podocarpus appear to have different origins, probably all reduced from multiovulate cones.

Base Sequence↗

PubMed2002

Transpecific microsatellites for hard pines.

Microsatellites are difficult to recover from large plant genomes so cross-specific utilisation is an important source of markers. Fifty microsatellites were tested for cross-specific amplification and polymorphism to two New World hard pine species, slash pine ( Pinus elliottii var. elliottii) and Caribbean pine ( P. caribaea var. hondurensis). Twenty-nine (58%) markers amplified in both hard pine species, and 23 of these 29 were polymorphic. Soft pine (subgenus Strobus) microsatellite markers did amplify, but none were polymorphic. Pinus elliottii var. elliottii and P. caribaea var. hondurensis showed mutational changes in the flanking regions and the repeat motif that were informative for Pinus spp. phylogenetic relationships. Most allele length variation could be attributed to variability in repeat unit number. There was no evidence for ascertainment bias.

Journal Article↗

PubMed2005

Succession after stand replacing disturbances by fire, wind throw, and insects in the dark Taiga of Central Siberia.

The dark taiga of Siberia is a boreal vegetation dominated by Picea obovata, Abies sibirica, and Pinus sibirica during the late succession. This paper investigates the population and age structure of 18 stands representing different stages after fire, wind throw, and insect damage. To our knowledge, this is the first time that the forest dynamics of the Siberian dark taiga is described quantitatively in terms of succession, and age after disturbance, stand density, and basal area. The basis for the curve-linear age/diameter relation of trees is being analyzed. (1) After a stand-replacing fire Betula dominates (4,000 trees) for about 70 years. Although tree density of Betula decreases rapidly, basal area (BA) reached >30 m2/ha after 40 years. (2) After fire, Abies, Picea, and Pinus establish at the same time as Betula, but grow slower, continue to gain height and eventually replace Betula. Abies has the highest seedling number (about 1,000 trees/ha) and the highest mortality. Picea establishes with 100-400 trees/ha, it has less mortality, but reached the highest age (>350 years, DBH 51 cm). Picea is the most important indicator for successional age after disturbance. Pinus sibirica is an accompanying species. The widely distributed "mixed boreal forest" is a stage about 120 years after fire reaching a BA of >40 m2/ha. (3) Wind throw and insect damage occur in old conifer stands. Betula does not establish. Abies initially dominates (2,000-6,000 trees/ha), but Picea becomes dominant after 150-200 years since Abies is shorter lived. (4) Without disturbance the forest develops into a pure coniferous canopy (BA 40-50 m2/ha) with a self-regenerating density of 1,000 coniferous canopy trees/ha. There is no collapse of old-growth stands. The dark taiga may serve as an example in which a limited set to tree species may gain dominance under certain disturbance conditions without ever getting monotypic.

Animals↗

PubMed2004

Antibacterial effects of knotwood extractives on paper mill bacteria.

Hydrophilic knotwood extracts from 18 wood species were assessed in disc diffusion and liquid culture tests for antibacterial effects against three species of paper mill bacteria. The Pinus sylvestris, P. resinosa, P. contorta, and P. banksiana extracts decreased or inhibited bacterial growth. The susceptibility order was P. sylvestris > P. resinosa > P. contorta > P. banksiana, correlating with the concentrations of pinosylvin and pinosylvin monomethyl ether in these wood species. Also, Pseudotsuga menziesii and Thuja occidentalis extracts had a small inhibitory effect. The Gram-positive Bacillus coagulans was more susceptible to the extracts than the Gram-negative Burkholderia multivorans and Alcaligenes xylosoxydans. The main components in the Pinus knotwood extracts were pinosylvin monomethyl ether and pinosylvin, suggesting these to be the active components. Therefore, pure pinosylvin, pinosylvin monomethyl ether, and dihydro-pinosylvin monomethyl ether were also tested. All compounds showed antibacterial effects. However, higher concentrations were needed for these pure compounds than for the knotwood extracts. Pinosylvin had stronger antibacterial effects than pinosylvin monomethyl ether. This work shows that knotwood extracts, especially from Pinus species, have a potential for use as natural biocides in papermaking.

Anti-Bacterial Agents↗

PubMed2000

Spatial variation of modern pollen in Oregon and southern Washington, USA.

Surface sediments from 95 lakes provide information on the spatial variation of modern pollen spectra in Oregon and southern Washington. Percentages for 13 pollen types were compared within and between vegetation zones to characterize regional patterns of pollen spectra. The percentage data were also compared with climate variables to determine relationships between pollen percentages and regional climate gradients. The composition of modern pollen spectra corresponds well with the distribution of the pollen producers. Most pollen assemblages were generally dominated by Pinus, but those west of the Cascade Range were dominated by Alnus. Low percentages of Pseudotsuga/Larix, Tsuga mertensiana, Abies, and Picea pollen coincided with local occurrence of the trees. The distributions of the pollen data were arranged along gradients of temperature and effective moisture. West of the Cascade Range, Alnus, Tsuga heterophylla, Pseudotsuga/Larix, and Cupressaceae pollen were abundant and correlate well with moderate temperature and high effective moisture. In the shrub-steppe and woodlands east of the Cascade Range, where effective moisture is low, Artemisia, Cupressaceae, and Pinus pollen were dominant. At high elevations, Pinus, T. mertensiana, Abies, and Picea were common pollen types in areas with short growing seasons and high effective moisture. Pollen percentages collected from lake surface sediments, moss polsters, and soils were compared within a number of vegetation types to assess their similarity. The three types of sample yielded similar results for forested areas, but lake sediment samples from upper- and lower-treeline sites captured a more regional picture of the vegetation.

Journal Article↗

PubMed2002

The discovery of three genetic races of the dwarf mistletoe Arceuthobium americanum (Viscaceae) provides insight into the evolution of parasitic angiosperms.

A population genetic approach was used to explore the evolutionary biology of the parasitic angiosperm Arceuthobium americanum Nutt. ex Engelm. (Viscaceae). Arceuthobium americanum infects three principal hosts and has the most extensive geographical range of any North American dwarf mistletoe. Based on the lack of apparent morphological and phenological differences between populations of A. americanum, past researchers have found no evidence for recognizing infraspecific taxa. In this study, molecular analysis using amplified fragment length polymorphism (AFLP) analysis indicated that A. americanum is divided into three distinct genetic races, each associated with a different host taxon in regions of allopatry: (i) Pinus banksiana in western Canada; (ii) Pinus contorta var. murrayana in the Sierra Nevada and Cascade Mountain ranges in the western US; and (iii) Pinus contorta var. latifolia in the western US and Canada. These observations suggest that host identity, geographical isolation and environmental factors have contributed to race formation in A. americanum. The lack of fine-scale patterning within each of the A. americanum races is attributed to random dispersal of seeds over long distances by animal vectors. Historical factors such as glaciations and founder events have also influenced structuring and genetic diversity in A. americanum populations. Given sufficient time, it is possible that these races will become reproductively isolated and undergo speciation.

Biological Evolution↗

PubMed1992

An account of the ticks of the northeastern of Spain (Acarina: Ixodidae).

The tick species commonly collected at the Northeast of Spain are reported in this paper. Data on hosts, temperature and humidity requirements, vegetation relationships, altitudinal distribution, and seasonal activity are included. R. sanguineus is commonly collected in areas with Mediterranean vegetation, esteppe, and semi-desertic esteppe, ranging from 190 to 1,000 meters above the sea level. R. sanguineus is related with sparse vegetal areas, and it is absent from areas with dense shrub or forests of every kind; sometimes, small populations may be collected in ecotones between Pinus spp. and esteppe formations. R. pusillus is closely related to areas of Mesomediterranean vegetation, sometimes subordinate to Pinus spp. and Quercus spp. The climate to which the species ally is always of continental type, with a hot and dry summer, and cold winter; although the species is commonly restricted to its main host, Oryctolagus cuniculus, several specimens have been collected from V. vulpes. Our data display the clear affinity of I. ricinus to the Supramediterranean vegetation (Aceri-Quercion faginae), places of Quercetum-Buxetum, as well as the Iberian Oromediterranean vegetation (Pinus sylvestris-Buxus sempervirens). Captures are scarce in forest of Fagus sylvatica, but data suggest that the species may be locally common on such places. Climate for the zones of collection of I. ricinus is Atlantic attenuated, with mild summers and humid winters. D. marginatus is strongly related to the xerophilic vegetation, widely spread through the Mediterranean, Supramediterranean, and hill levels, but does not colonize the true Oromediterranean vegetation. In our captures, the species is commonly collected in pubescent oak formations, but it does not penetrate in true forest associations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Simulated influence of leaf geometry on sunlight interception and photosynthesis in conifer needles.

The light interception capabilities of individual conifer needles are governed by their cross-sectional geometry and their orientation to sunlight. Leaf cross sections typical of conifer tree species were modeled to quantify the interception of direct sunlight over a range of incident light angles. The needle shapes exhibited by Abies nordmanniana Spach, Picea asperata Master, Pinus cembra L., P. monophylla Torr & Frém., and P. sylvestris L. were selected because they are representative of the range of geometric shapes found in conifer tree species. Calculated light interception values were compared to corresponding predictions for a laminar broadleaf. Estimates of carbon gain were derived from computed incident light integrated over the leaf cross section and a representative curve of conifer photosynthetic response to light. Flat leaf cross sections (e.g., Abies nordmanniana) with high surface area to volume ratios (> 6) intercepted more light per unit area at high angles of incidence than thick leaves. Thick leaves (e.g., Pinus cembra) intercepted more light at low angles of incidence than at high angles of incidence. Needles of Pinus monophylla had no angular dependence for light interception because of their circular cross section. Large differences in estimated CO(2) assimilation occurred among the species, especially when CO(2) uptake was expressed on a unit volume basis. A maximum uptake of 67.9 mmol CO(2) m(-3) s(-1) was predicted for A. nordmanniana compared to a minimum of 39.7 mmol m(-3) s(-1) for P. monophylla. A greater angular dependence occurred for estimates of CO(2) uptake than for estimates of light interception.

Journal Article↗

PubMed1997

Vertical gradients in photosynthetic gas exchange characteristics and refixation of respired CO(2) within boreal forest canopies.

We compared vertical gradients in leaf gas exchange, CO(2) concentrations, and refixation of respired CO(2) in stands of Populus tremuloides Michx., Pinus banksiana Lamb. and Picea mariana (Mill.) B.S.P. at the northern and southern boundaries of the central Canadian boreal forest. Midsummer gas exchange rates in Populus tremuloides were over twice those of the two conifer species, and Pinus banksiana rates were greater than Picea mariana rates. Gas exchange differences among the species were attributed to variation in leaf nitrogen concentration. Despite these differences, ratios of intercellular CO(2) to ambient CO(2) (c(i)/c(a)) were similar among species, indicating a common balance between photosynthesis and stomatal conductance in boreal trees. At night, CO(2) concentrations were high and vertically stratified within the canopy, with maximum concentrations near the soil surface. Daytime CO(2) gradients were reduced and concentrations throughout the canopy were similar to the CO(2) concentration in the well-mixed atmosphere above the canopy space. Photosynthesis had a diurnal pattern opposite to the CO(2) profile, with the highest rates of photosynthesis occurring when CO(2) concentrations and gradients were lowest. After accounting for this diurnal interaction, we determined that photosynthesizing leaves in the understory experienced greater daily CO(2) concentrations than leaves at the top of the canopy. These elevated CO(2) concentrations were the result of plant and soil respiration. We estimated that understory leaves in the Picea mariana and Pinus banksiana stands gained approximately 5 to 6% of their carbon from respired CO(2).

Journal Article↗

PubMed1990

Estimation of leaf area index in fourteen southern Wisconsin forest stands using a portable radiometer.

Projected leaf area index (LAI) and Beer-Lambert Law extinction coefficients (K) were estimated for 28-year-old Picea abies (L.) Karst., Larix decidua Mill., Pinus resinosa Ait., and Pinus strobus L. plantations using vertical profile data obtained with a portable integrating radiometer (sunfleck ceptometer). Predicted LAI values were compared with direct measures of LAI. Based on dimensional analysis, LAI ranged from 5.0 for Larix decidua to 10.5 for Picea abies. Significant inverse relationships between cumulative LAI and canopy transmitted radiation were observed for the four species (R(2) = 0.92-0.97). Beer-Lambert extinction coefficients ranged from 0.39 for Picea abies to 0.84 for Pinus strobus. Stand-level predictions of LAI based on the Beer-Lambert Law were compared with measured LAI values for eight conifer and six broadleaf stands. Using local K estimates resulted in predicted LAI values with an average 6% error. Using published K values resulted in an average error of 20%. High LAI and concomitantly low light levels below the canopy of Picea abies stands resulted in large overestimation errors in predicted LAI, rendering the sunfleck ceptometer inappropriate for forests with large LAIs.

Journal Article↗

PubMed1987

Investigations on the Nature of the Auxin-Wave in the Cambial Region of Pine Stems : Validation of IAA as the Auxin Component by the Avena Coleoptile Curvature Assay and by Gas Chromatography-Mass Spectrometry-Selected Ion Monitoring.

The major auxin of Scots pine (Pinus silvestris L.) which is transported basipetally into agar strips from the cambial region of the stem was quantified by the Went Avena coleoptile curvature assay before and after reversed phase C(18) high performance liquid chromatography (HPLC), and then identified by full spectrum gas chromatography-mass spectrometry (GC-MS) as indole-3-acetic acid (IAA). The IAA was subsequently quantified by GC-MS-selected ion monitoring (SIM) using an internal standard of [(13)C]-(C(6))-IAA. The amount of IAA collected into 22-millimeter long agar strips during 10 minutes of contact with the stem cambial region was estimated by GC-MS-SIM and the Went bioassay to be 2.3 and 2.1 nanograms per strip, respectively. The GC-MS technique thus confirmed the results obtained by the Went curvature assay. The Avena curvature assay revealed the presence of at least one other, more polar (based on HPLC retention time) auxin that diffused into the agar strips with the IAA. Its bioactivity was only 5% of the IAA fraction. Its HPLC retention time was earlier than IAA-glucoside, IAA-aspartate, or IAA-glycine, but the same as IAA-inositol. No significant amounts of inhibitors or synergists of IAA activity on the Avena assay were found in extracts corresponding to one or five strips of agar. Thus, the direct bioassay of the agar strips immediately after their removal from the cambial region of P. silvestris stem sections reflects the concentration of the native IAA. For both P. silvestris and lodgepole pine (Pinus contorta) a wavelike pattern of auxin stimulation of Avena curvature was found in agar strips exposed for only 10 minutes to the basal ends of an axial series of 6-millimeter long sections from the cambial region of the stem. This wavelike pattern was subsequently confirmed for P. contorta both by Avena curvature assay and by GC-MS-SIM of HPLC fractions at the retention time of [(3)H]IAA. The wavelike pattern of auxin diffusing from the cambial region of Pinus has thus been determined to consist primarily of IAA and this pattern has now been quantitated using both the Went Avena curvature assay and GC-MS-SIM with [(13)C]-C(6)-IAA as an internal standard.

Journal Article↗