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PubMed1995

Dynamic response of stomata to changing irradiance in loblolly pine (Pinus taeda L.).

Dynamic changes in stomatal conductance and the rate of photosynthesis were measured as periods of shading (decrease in irradiance from 800 to 200 micro mol m(-2) s(-1)) between 5 and 60 min were imposed on needles of Pinus taeda L. trees under laboratory conditions. Shading induced a 39% decrease in stomatal conductance but the rate of change was slow. Average time constants (+/- standard error) were shorter for the decrease in stomatal conductance when shading was imposed for 30 min (14.8 +/- 1.3 min) than for the increase in stomatal conductance when shading was removed (25.5 +/- 3.4 min). The time constants for increasing stomatal conductance when shading was removed were linearly related to the length of the previous dark period. The rate of photosynthesis fell immediately by 58% when shading was imposed and increased more rapidly than the change in stomatal conductance when shading was removed. The increase in photosynthesis during the induction phase after shading was removed was limited by both stomatal and biochemical effects. The long time constants for stomatal response contributed to the poor correlations between stomatal conductance and instantaneous measurements of irradiance from field data. However, the slow response of stomatal conductance to changes in irradiance had little effect on total daily transpiration, carbon gain and water-use efficiency.

Journal Article↗
PubMed2004

Species richness and seasonal abundance of ectomycorrhizal fungi in plantations of Eucalyptus dunnii and Pinus taeda in southern Brazil.

The abundance and diversity of ectomycorrhizal fungi (EMF) was assessed based on the collection of basidiocarps during 12 months comprising the spring of 1995, and the summer, autumn, and winter of 1996, in three stands of young, middle-aged, and rotation age plantations of Pinus taeda and Eucalyptus dunnii, in the state of Santa Catarina, southern Brazil. A total of 3,085 collections yielded 34 presumed EMF taxa in ten genera, including mushroom-like and sequestrate species. Fruiting patterns of EMF differed with host and season, and host specificity was apparent in some. The overall relative importance (RI) and the Shannon diversity index (H) suggested that stands of E. dunnii had a more diverse aboveground EMF community than those of P. taeda. Overall, species of Scleroderma and Laccaria were not only the most abundant but also had the highest biomass values. The results show that a small number of species of abundant biomass and a larger number of species of less-abundant biomass characterize each forest class.

Biodiversity↗
PubMed1998

Canopy conductance of Pinus taeda, Liquidambar styraciflua and Quercus phellos under varying atmospheric and soil water conditions.

Sap flow, and atmospheric and soil water data were collected in closed-top chambers under conditions of high soil water potential for saplings of Liquidambar styraciflua L., Quercus phellos L. and Pinus taeda L., three co-occurring species in the southeastern USA. Responses of canopy stomatal conductance (g(t)) to water stress induced by high atmospheric water vapor demand or transpiration rate were evaluated at two temporal scales. On a diurnal scale, the ratio of canopy stomatal conductance to maximum conductance (g(t)/g(t,max)) was related to vapor pressure deficit (D), and transpiration rate per unit leaf area (E(l)). High D or E(l) caused large reductions in g(t)/g(t,max) in L. styraciflua and P. taeda. The response of g(t)/g(t,max) to E(l) was light dependent in L. styraciflua, with higher g(t)/g(t,max) on sunny days than on cloudy days. In both L. styraciflua and Q. phellos, g(t)/g(t,max) decreased linearly with increasing D (indicative of a feed-forward mechanism of stomatal control), whereas g(t)/g(t,max) of P. taeda declined linearly with increasing E(l) (indicative of a feedback mechanism of stomatal control). Longer-term responses to depletion of soil water were observed as reductions in mean midday g(t)/g(t,max), but the reductions did not differ significantly between species. Thus, species that employ contrasting methods of stomatal control may show similar responses to soil water depletion in the long term.

Journal Article↗
PubMed1986

Accumulation of starch in roots and foliage of loblolly pine (Pinus taeda L.): effects of season, site and fertilization.

Accurate predictions of stand response to nitrogen fertilization require a better understanding of the plant processes associated with stand nutrition. This study examined the relationship between stand nutrition and starch accumulation in roots and foliage of loblolly pine (Pinus taeda L.). A field study was located on the lower Coastal Plain of North Carolina on four sites of differing soil types. Stands of 8-year-old trees were fertilized with nitrogen (225 kg ha(-1)) or nitrogen plus phosphorus (225 kg N ha(-1) + 75 kg P ha(-1)) in 1981. Roots and foliage were collected from five trees per plot at six sampling dates from July 1983 through January 1985 and analyzed for starch. Starch concentrations showed seasonal fluctuations, with levels generally highest in early spring prior to budbreak. Root starch concentrations were lowest in autumn, whereas foliar concentrations were lowest in winter.

Journal Article↗
PubMed2000

Seasonal CO(2) assimilation and stomatal limitations in a Pinus taeda canopy.

Net CO(2) assimilation (A(net)) of canopy leaves is the principal process governing carbon storage from the atmosphere in forests, but it has rarely been measured over multiple seasons and multiple years. I measured midday A(net) in the upper canopy of maturing loblolly pine (Pinus taeda L.) trees in the piedmont region of the southeastern USA on 146 sunny days over 36 months. Concurrent data for leaf conductance and photosynthetic CO(2) response curves (A(net)-C(i) curves) were used to estimate the relative importance of stomatal limitations to CO(2) assimilation in the field. In fully expanded current-year and 1-year-old needles, midday light-saturated A(net) was constant over much of the growing season (5-6 &mgr;mol CO(2) m(-2) s(-1)), except during drought periods. During the winter season (November-March), midday A(net) of overwintering needles varied in proportion to leaf temperature. Net CO(2) assimilation at light saturation occurred when daytime air temperatures exceeded 5-6 degrees C, as happened on more than 90% of the sunny winter days. In both age classes of foliage, winter carbon assimilation accounted for approximately 15% of the daily carbon assimilation on sunny days throughout the year, and was relatively insensitive to year-to-year differences in temperature during this season. However, strong stomatal limitations to A(net) occurred as a result of water stress associated with freezing cycles in winter. During the growing season, drought-induced water stress produced the largest year-to-year differences in seasonal CO(2) assimilation on sunny days. Seasonal A(net) was more drought sensitive in current-year needles than in 1-year-old needles. Relative stomatal limitations to daily integrated A(net) were approximately 40% over the growing season, and summer drought rather than high temperatures had the largest impact on summer A(net) and integrated annual CO(2) uptake in the upper crown. Despite significant stomatal limitations, a long duration of near-peak A(net) in the upper crown, particularly in 1-year-old needles, conferred high seasonal and annual carbon gain.

Journal Article↗
PubMed2006

Diterpene resin acid biosynthesis in loblolly pine (Pinus taeda): functional characterization of abietadiene/levopimaradiene synthase (PtTPS-LAS) cDNA and subcellular targeting of PtTPS-LAS and abietadienol/abietadienal oxidase (PtAO, CYP720B1).

Diterpene resin acids are prominent defense compounds against insect pests and pathogens in conifers. Biochemical and molecular analyses in grand fir (Abies grandis), Norway spruce (Picea abies), and loblolly pine (Pinus taeda) have identified two classes of genes and enzymes that generate much of the structural diversity of terpenoid defense compounds: The terpenoid synthases (TPS) and cytochrome P450 monooxgenases (P450). Using a single substrate, geranylgeranyl diphosphate, families of single-product and multi-product diterpene synthases generate an array of cyclic diterpene olefins. These diterpenes are converted to diterpene resin acids by activity of one or more P450 enzymes. A few conifer diterpene synthases have previously been cloned and characterized in grand fir and in Norway spruce. We have also previously shown that the loblolly pine P450 abietadienol/abietadienal oxidase (PtAO) catalyzes multiple oxidations of several diterpene alcohols and aldehydes. Conifer diterpene synthases are thought to function in plastids while P450s can also be localized to plastids or to the endoplasmic reticulum (ER). Here, we show that a loblolly pine cDNA (PtTPS-LAS) encodes a typical multi-product conifer diterpene synthase that forms levopimaradiene, abietadiene, palustradiene, and neoabietadiene similar to the grand fir abietadiene synthase and Norway spruce levopimaradiene/abietadiene synthase. Subcellular targeting of PtTPS-LAS and PtAO to plastids and ER, respectively, was shown with green fluorescent fusion protein expression in tobacco cells. These data suggest that enzymes for conifer diterpene resin acid biosynthesis are localized to at least two different subcellular compartments, plastids and ER, requiring efficient transport of intermediates and secretion of diterpene resin acids into the extracelluar space.

Alkyl and Aryl Transferases↗
PubMed2002

Genetic analysis of growth curves for a woody perennial species, Pinus taeda L.

Inheritance of growth curves is critical for understanding evolutionary change and formulating efficient breeding plans, yet has received limited attention. Growth curves, like other characters that change in concert with development, often have higher heritability than age-specific traits. This study compared genetic parameters of height-growth curves with those of age-specific heights for a conifer, Pinus taeda L. Growth curves were fitted with: (1) a linear regression model, and (2) a non-linear model based on Richards' function using two sources of height data: two six-parent diallel tests assessed at age 2 to 10 years and two tests from a nested mating design with 222 parents assessed at 1 to 25 years. Additive genetic control of growth-curve parameters was moderate (h(2) = 0.06 to 0.26) and slightly lower than that for age-specific heights. Additive variance exceeded dominance variance for rate and shape parameters, but not for the asymptote. Genetic correlations among growth-curve parameters were high. Early selection on height was as efficient as selection on growth-curve parameters.

Journal Article↗
PubMed1986

Free proline changes in Pinus taeda L. callus in response to drought stress.

The amino acid, proline (PRO), may have an important role in plant adaptation to drought stress. To study the effect of drought stress on PRO content of pine tissues, we measured free PRO by high pressure liquid chromatography in control ( -0.4 MPa) and drought-stressed ( -0.8, -1.0, -1.3, -1.6 MPa) callus tissue of Pinus taeda L. after eight weeks of growth. Drought stress was induced by adding polyethylene glycol (PEG) to the nutrient media. The relation between PRO accumulation and water potential was influenced by composition of the medium and temperature. Callus growing in media with water potentials of -0.8 MPa showed no increase in PRO compared to control callus in media at -0.4 MPa. When callus tissue was subjected to low water potentials (-1.6 MPa), endogenous PRO concentration increased 40-fold, while callus fresh weight decreased by more than 90%. When exogenous PRO was added to the nutrient media, endogenous PRO was directly proportional to the exogenous PRO concentration rather than reduction in callus growth. Thus low water potential in callus results in endogenous PRO accumulation and large reductions in callus fresh weight growth. Proline accumulation in pine cells appears to be related to mechanisms associated with tolerance to desiccation.

Journal Article↗
PubMed2004

Canopy position affects photosynthetic adjustments to long-term elevated CO2 concentration (FACE) in aging needles in a mature Pinus taeda forest.

Few studies have examined the effects of elevated CO2 concentration ([CO2]) on the physiology of intact forest canopies, despite the need to understand how leaf-level responses can be aggregated to assess effects on whole-canopy functioning. We examined the long-term effects of elevated [CO2] (ambient + 200 ppm CO2) on two age classes of needles in the upper and lower canopy of Pinus taeda L. during the second through sixth year of exposure to elevated [CO2] in free-air (free-air CO2 enrichment (FACE)) in North Carolina, USA. Strong photosynthetic enhancement in response to elevated [CO2] (e.g., +60% across age classes and canopy locations) was observed across the years. This stimulation was 33% greater for current-year needles than for 1-year-old needles in the fifth and sixth years of treatment. Although photosynthetic stimulation in response to elevated [CO2] was maintained through the sixth year of exposure, we found evidence of concurrent down-regulation of Rubisco and electron transport capacity in the upper-canopy sunlit leaves. The lower canopy showed no evidence of down-regulation. The upper canopy down-regulated carboxylation capacity (Vcmax) and electron transport capacity (Jmax) by about 17-20% in 1-year-old needles; however, this response was significant across sampling years only for Jmax in 1-year-old needles (P < 0.02). A reduction in leaf photosynthetic capacity in aging conifer needles at the canopy top could have important consequences for canopy carbon balance and global carbon sinks because 1-year-old sunlit needles contribute a major proportion of the annual carbon balance of these conifers. Our finding of a significant interaction between canopy position and CO2 treatment on the biochemical capacity for CO2 assimilation suggests that it is important to take canopy position and needle aging into account because morphologically and physiologically distinct leaves could respond differently to elevated [CO2].

Carbon Dioxide↗
PubMed2004

Belowground carbon dynamics in loblolly pine (Pinus taeda) immediately following diammonium phosphate fertilization.

Forest soils store an immense quantity of labile carbon (C) and a may be a large potential sink for atmospheric C. Forest management practices such as fertilization may enhance overall C storage in soils, yet changes in physiological processes following nutrient amendments have not been widely investigated. We intensively monitored belowground C dynamics for nearly 200 days following diammonium phosphate fertilization of pot-grown loblolly pine (Pinus taeda L.) seedlings in an effort to examine the short-term effects of fertilization on processes involved in soil C sequestration. Soil respiration rates initially increased in fertilized pots relative to controls, followed by a brief reversal in this trend and then a final sustained pattern of elevated rates of soil respiration in the fertilized treatment. Patterns in soil respiration rates over time reflected changes in autotrophic (root) and heterotrophic (microbial) components of soil respiration. Root respiration rates were greater in the fertilized treatment 49 days following fertilization and returned to control rates by the end of the study. In contrast, microbial respiration rates and microbial activity per soil C concentration remained depressed over the same time period. Compared with control seedlings, total root biomass was 27% greater in fertilized seedlings harvested at the end of the study, indicating that the elevated soil respiration rates observed toward the end of the study were a result of increased respiring root biomass. We conclude that fertilization, at least over the short-term, may increase soil C sequestration by increasing belowground biomass production and reducing microbial driven C turnover.

Biomass↗
PubMed1987

Physiology and genetics of tree growth response to moisture and temperature stress: an examination of the characteristics of loblolly pine (Pinus taeda L.).

Water stress and temperature impose fundamental limits to forest productivity. Stresses caused by fluctuating or extreme temperatures or limited water availability vary both seasonally and from year to year. The role of these stresses should be considered when investigating the causes of declines in forest productivity. Forest growth, or carbon gain, can be related quantitatively to three components: leaf area, rate of net photosynthesis and rate of respiration. This paper examines effects of temperature and water supply on these components with particular reference to loblolly pine (Pinus taeda L.), a species of economic importance in the southeastern United States where declines, of unknown cause, in forest productivity have been reported.

Journal Article↗
PubMed2000

The influence of elevated ultraviolet-B radiation (UV-B) on tissue quality and decomposition of loblolly pine (Pinus taeda L.) needles.

Stratospheric ozone depletion is expected to elevate the influx of ultraviolet-B radiation (UV-B) to the biosphere. Increased levels of UV-B may, in turn, alter important ecosystem processes such as decomposition. Previous studies have shown that growth under elevated UV-B can alter leaf quality in angiosperm species and thereby indirectly change subsequent rates of leaf decay. In this experiment, we determined if elevated UV-B would alter the chemical composition and decay of needle tissue from two seed sources of the gymnosperm Pinus taeda L. Maryland and Virginia seed sources of P. taeda were grown in the field for 3 years beneath lampbanks supplying either ambient, low elevated or high elevated UV-B. These levels of UV-B corresponded to 0, 16 and 25% stratospheric ozone depletion at the experimental site in Beltsville, MD (39 degrees N). Needles were collected from six randomly chosen plants for each combination of seed source and UV-B level. The needle samples were analyzed for total C and N, UV-B absorbing compounds, and carbon fractions. Decay rates were also determined by measuring rates of CO(2) evolution from needle material decomposed under laboratory conditions. UV-B did not significantly alter the chemical composition of needles from the Virginia seed source. In contrast, needles from the Maryland seed source tended to have elevated lignin/N ratios and a lower holocellulose content when grown under the highest level of UV-B. Furthermore, while needles from the Virginia pines did not have UV-B altered decay rates, Maryland needles grown under low elevated UV-B conditions decomposed 36% more rapidly than needles from other treatments. Results from this experiment illustrate at least three characteristics about the indirect effect of UV-B on decomposition, (1) UV-B can modify decomposition of tissue from gymnosperms as well as angiosperms; (2) UV-B effects on tissue chemistry and decay may not only be species-specific but also seed-source specific; and (3) UV-B effects on decomposition may not increase with increasing UV-B dose.

Journal Article↗
PubMed2001

Regeneration of transgenic loblolly pine (Pinus taeda L.) from zygotic embryos transformed with Agrobacterium tumefaciens.

Embryos of 24 open-pollinated families of loblolly pine (Pinus teade L.) were used as explants to conduct in vitro regeneration. Then, Agrobacterium tumefaciens strain GV3101 harboring the plasmid pPCV6NFHygGUSINT was used to transform mature zygotic embryos of seven families of loblolly pine. The frequency of transformation varied among families infected with A. tumefaciens. The highest frequency (100%) of transient beta-glucuronidase (GUS)-expressing embryos was obtained from family 11-1029 with over 300 blue spots per embryo. Expression of the GUS reporter gene was observed in cotyledons, hypocotyls, and radicles of co-cultivated mature zygotic embryos, as well as in callus and shoots derived from co-cultivated mature zygotic embryos. Ninety transgenic plants were regenerated from hygromycin-resistant callus derived from families W03. 8-1082 and 11-1029. and 19 transgenic plantlets were established in soil. The presence of the GUS gene in the plant genome was confirmed by polymerase chain reaction. Southern blot, and plant DNA/T-DNA junction analysis. These results suggest that an efficient A. tumefaciens-mediated transformation protocol for stable integration of foreign genes into loblolly pine has been developed and that this transformation system could be useful for future studies on transferring economically important genes to loblolly pine.

Agrobacterium tumefaciens↗
PubMedDate not supplied

[Larvae culture of ovine gastrintestinal nematodes in sawdust substrates of Pinus taeda, P. elliottii and Araucaria angustifolia].

The aim of this study was to verify the influence of sawdust substrates obtained from wood treated with sodium tribromophenate and not treated of Pinus elliotti, P. taeda, and Araucaria angustifolia in larval cultures of ovine gastrintestinal helminths. Feces samples were collected between 8 to 12am, from a lamb naturally infected with gastrintestinal nematodes and analysed by the modified Mc Master technique for worm egg counting (epg). Six groups of 20g of feces were prepared. Each group received 5g of one of the sawdust substrates and 5ml of distilled water. The material has been processed, identified and taken to a climatized chamber with a temperature of 27 +/- 1 degrees C, relative humidity above 70%, and in escotophase for seven days. The third stage larvae were recovered by the Baermann technique after four hours of sedimentation for the counting and identification of one hundred larvae per treatment. For each treatment were realized 10 repetitions. The average of EPG of Strongylida Order was 630. The average of the larvae number obtained in 20 grams of feces and the percentage of recovery in the different substrates based on the EPG was: P. taeda treated, 2719 (22.66%) and not treated, 2353 (20.08%); P. elliotti treated, 3069 (22.48%) and not treated, 3181 (24.54%); A. angustifolia treated, 2370 (18.73%) and not treated, 3361 (26.75%). There was no statistic difference in 5% level of significance between the averages and the number of larvae in the different substrates.

Animals↗
PubMed2001

[Causal factors of decline disease in exotic pine (Pinus taeda and P. elliottii) plantations].

Investigation on the cause of the decline of exotic pine plantations in Anhui Province was carried out from 1995 to 2000. The results showed that the cause might develop from the interaction of three or more sets of factors. The first group of factors called as predisposing factors were high and low temperature and rainfall, poor soil fertility, and excessive soil bulk density, soil moisture, and of stand density; the second group of factors called as inciting factors were insect defoliators, damaging diseases of needles, late spring frost, severe drought, and excessive resin-tapping, and the third group of factors called as contributing factors were several biotic agents such as shoot blight infected by Sphaeropsis sapinea, decay wood and root rot by fungi, and bark beetles and wood borers.

Causality↗
PubMed1997

Expression analysis of a gene family in loblolly pine (Pinus taeda L.) induced by water deficit stress.

A cDNA clone (lp3) from loblolly pine induced by water deficit stress (WDS) has been isolated. It is preferentially induced in roots with a constitutive basal level of expression also observed in stems and needles. Northern blot analysis with well irrigated ABA-treated seedlings indicated that the overall accumulation of lp3 transcripts in the roots was lower than that of water deficit-stressed seedlings. However, within roots, lp3 was induced by ABA indicating that the expression of lp3 in roots under WDS conditions was partly mediated by ABA. The lp3 clone is similar to a group of genes called asr (ABA stress and ripening) genes identified in several species. A genomic clone (lp3-1) was identified and its putative protein has the hydrophylicity profile similar to that of lp3 except for two deletions in the 5' region. The genomic Southern and RT-PCR (reverse transcriptase-polymerase chain reaction) analyses indicate that the lp3 gene belongs to a small multigene family of at least four members with a distinct pattern of expression during WDS.

Amino Acid Sequence↗