Integrating within-crown variation in net photosynthesis in loblolly and slash pine families

We examined photosynthetic characteristics of two fast- and two slow-growing half-sib families of both loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii var. elliottii Engelm.) on two sites in northern Florida to: (1) quantify variation in light-saturated net photosynthesis (Amax) associated with vertical crown position and foliage age; (2) quantify the amount and distribution of leaf area by foliage age class; and (3) determine whether photosynthetic indices, ranging from leaf-level through whole-crown Amax, were related to growth differences among species and families. In both species, leaf-level Amax was higher in more recently formed foliage both within the same year (where Amax in the third flush averaged 10 to 30% higher than Amax in the first flush) and between years (where Amax in current-year foliage averaged 20 to 40% higher than Amax in 1-year-old foliage). When expressed on a leaf area basis, Amax of current-year foliage was higher in slash pine than in loblolly pine, but Amax expressed on a mass basis did not differ between species. Loblolly pine had higher whole-tree leaf area than slash pine, whereas whole-tree Amax did not differ between species. When the mean values for fast-growing families were compared with the mean values for slow-growing families, there were no differences in leaf-level characteristics, whereas at the whole-tree level, fast-growing families had higher leaf area and whole-tree Amax than slow-growing families in both species. When comparisons were made among the individual fast- and slow-growing families, however, results were more variable. In both species, stem volume growth was strongly correlated with whole-tree Amax, with most of the strength of the correlation deriving from the relationship between volume growth and tree leaf area.     

Post-fertilization physiology and growth performance of loblolly pine clones

The physiological processes leading to enhanced growth of loblolly pine (Pinus taeda L.) following fertilization are not clearly understood. Part of the debate revolves around the temporal response of net photosynthetic rate (A(n)) to fertilization and whether the A(n) response is always positive. We measured light-saturated photosynthetic rate (A(sat)), dark respiration rate, growth and crown silhouette area in eight clones of loblolly pine before and after nitrogen (N) fertilization (112 kg ha(-1)) to track the initial physiological changes prior to any changes in growth. Overall, there were positive photosynthetic and growth responses to fertilization; however, there were pronounced physiological and growth differences among clones, even among clones with the same parents. Clones 4, 6 and 7 showed large volume growth and A(sat) responses to fertilization. Clone 1 and Clone 8 (a full-sibling of Clone 7) mainly showed a volume growth response, whereas Clone 2 (full-sibling of Clone 1) showed an A(sat) response only. Clone 5 (full-sibling of Clone 6) showed little response to fertilization, whereas Clone 3 (full-sibling of Clone 4) showed a negative A(sat) response. Thus, within-family variation warrants further study to ensure that relatively expensive clonal material is used efficiently.     

Aluminum sensitivity of loblolly pine and slash pine seedlings grown in solution culture

To probe variation in Al sensitivity of two co-occurring pine species, seedlings from six full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were grown in solution culture containing 4.4 mM (high-Al) or 0.01 mM (low-Al) AlCl(3) at pH 4 for 58 days. On average, both pine species had 41% less total dry weight in the high-Al treatment than in the low-Al treatment. Stem volume growth of slash pine was more sensitive to the high-Al treatment than that of loblolly pine. In both species, the high-Al treatment inhibited root dry weight more than shoot dry weight. Within-species variation in Al sensitivity among families was greater in loblolly pine (24 to 52% inhibition of seedling dry weight) than in slash pine (35 to 47% inhibition of seedling dry weight). Foliar Al concentration was positively correlated with Al sensitivity in slash pine but not in loblolly pine; however, in both species, the concentration of Al in roots was 20-fold greater than in foliage.     

Genetic effects on total phenolics, condensed tannins and non-structural carbohydrates in loblolly pine (Pinus taeda L.) needles

Carbon allocation to soluble phenolics (total phenolics, proanthocyanidins (PA)) and total non-structural carbohydrates (TNC; starch and soluble sugars) in needles of widely planted, highly productive loblolly pine (Pinus taeda L.) genotypes could impact stand resistance to herbivory, and biogeochemical cycling in the southeastern USA. However, genetic and growth-related effects on loblolly pine needle chemistry are not well characterized. Therefore, we investigated genetic and growth-related effects on foliar concentrations of total phenolics, PA and TNC in two different field studies. The first study contained nine different genotypes representing a range of genetic homogeneity, growing in a 2-year-old plantation on the coastal plain of North Carolina (NC), USA. The second study contained eight clones with different growth potentials planted in a 9-year-old clonal trial replicated at two sites (Georgia (GA) and South Carolina (SC), USA). In the first study (NC), we found no genetic effects on total phenolics, PA and TNC, and there was no relationship between genotype size and foliar biochemistry. In the second study, there were no differences in height growth between sites, but the SC site showed greater diameter (diameter at breast height (DBH)) and volume, most likely due to greater tree mortality (lower stocking) which reduced competition for resources and increased growth of remaining trees. We found a significant site?×?clone effect for total phenolics with lower productivity clones showing 27-30% higher total phenolic concentrations at the GA site where DBH and volume were lower. In contrast to the predictions of growth-defense theory, clone volume was positively associated with total phenolic concentrations at the higher volume SC site, and PA concentrations at the lower volume GA site. Overall, we found no evidence of a trade-off between genotype size and defense, and genetic potential for improved growth may include increased allocation to some secondary metabolites. These results imply that deployment of more productive loblolly pine genotypes will not reduce stand resistance to herbivory, but increased production of total phenolics and PA associated with higher genotype growth potential could reduce litter decomposition rates and therefore, nutrient availability.     

Preliminary Studies on Establishment of Genetic Transformation System in Loblolly Pine

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Preliminary studies on establishment of genetic transformation system in loblolly pine

A transformation system was established for loblolly pine (Pinus taeda L.) mature zygotic embryos usingAgrobacterium tumefaciens. The gene coding for the β-glucuronidase (GUS) gene was introduced into loblolly pine tissues and its transient expression was detected with histochemical staining. The influences of different genotypes.Agrobacterum concentrations. and cocultivation time on GUS expression and kanamycin resistant callus and shoot regeneration were investigated. The results showed that the highest GUS expression frequency (16.3%) and shoot regeneration frequency (78%) were obtained from genotype 9–1003 withAgrobacterium concentration decreased 9 times and cocultivation time of 56 hours respectively. GUS expression was obtained in all genotypes tested. The successful expression of the GUS gene in different genotypes suggested that it will be a useful transformation system for loblolly pine. (Responsible Editor: Chai Ruihai)     

Branch growth and gas exchange in 13-year-old loblolly pine (Pinus taeda) trees in response to elevated carbon dioxide concentration and fertilization

We used whole-tree, open-top chambers to expose 13-year-old loblolly pine (Pinus taeda L.) trees, growing in soil with high or low nutrient availability, to either ambient or elevated (ambient + 200 micromol mol-1) carbon dioxide concentration ([CO2]) for 28 months. Branch growth and morphology, foliar chemistry and gas exchange characteristics were measured periodically in the upper, middle and lower crown during the 2 years of exposure. Fertilization and elevated [CO2] increased branch leaf area by 38 and 13%, respectively, and the combined effects were additive. Fertilization and elevated [CO2] differentially altered needle lengths, number of fascicles and flush length such that flush density (leaf area/flush length) increased with improved nutrition but decreased in response to elevated [CO2]. These results suggest that changes in nitrogen availability and atmospheric [CO2] may alter canopy structure, resulting in greater foliage retention and deeper crowns in loblolly pine forests. Fertilization increased foliar nitrogen concentration (N(M)), but had no consistent effect on foliar leaf mass (W(A)) or light-saturated net photosynthesis (A(sat)). However, the correlation between A(sat) and leaf nitrogen per unit area (N(A) = W(A)N(M)) ranged from strong to weak depending on the time of year, possibly reflecting seasonal shifts in the form and pools of leaf nitrogen. Elevated [CO2] had no effect on W(A), N(M) or N(A), but increased A(sat) on average by 82%. Elevated [CO2] also increased photosynthetic quantum efficiency and lowered the light compensation point, but had no effect on the photosynthetic response to intercellular [CO2], hence there was no acclimation to elevated [CO2]. Daily photosynthetic photon flux density at the upper, middle and lower canopy position was 60, 54 and 33%, respectively, of full sun incident to the top of the canopy. Despite the relatively high light penetration, W(A), N(A), A(sat) and R(d) decreased with crown depth. Although growth enhancement in response to elevated [CO2] was dependent on fertilization, [CO2] by fertilization interactions and treatment by canopy position interactions generally had little effect on the physiological parameters measured.     

Genetic transformation of loblolly pine using mature zygotic embryo explants by Agrobacterium tumefaciens

Introduction1Genetictransformationinconifershasthepotentialtoallowtheselectiveimprovementofindividualtraitsinelitecloneswhilestillmaintainingtheexistingcombinationofgenesresponsibleforthesuperiorphenotype(Charestetal.1991;Jamesetal.1996;Walteretal.1999).Atpresent,althoughconsiderableresearchefforthasbeendevotedtothegeneticengineeringofconiferspecies(Sederoffetal.1986;Bekkauoietal.1988,1990;Robertsonetal.1992;Bomminenietal.1993;Shinetal.1994;Klimaszewskaetal.1997),ithaslaggedbehindadvancesma…     

Growth and survival of lodgepole pine and Scots pine after 25 years in a reciprocal transplant experiment in Canada and Sweden

Lodgepole pine is native to western North America, but it is also planted as a fast-growing alternative to Scots pine in Sweden. The production of these two species, when grown as native and as exotic species, was compared in a transcontinental two-species provenance experiment. The tests were planted in 1986 on five sites in northwestern Canada and two sites in Sweden, and included full-sib families, half-sib families, seed orchard collections and natural stand seed collections of both species. After 25 years, lodgepole pine produced 48% more volume (m³ha^?1) and had 27% higher survival than Scots pine at one Swedish site, and had similar volume production and survival at a second. In the five Canadian sites, Scots pine produced on average 22% more volume than lodgepole pine. The variation between sites was, however, large. This higher volume of Scots pine in Canada could be due to higher survival (+28%) and less frequent damage; but higher top height for lodgepole pine in Canada indicated higher potential productivity. The results indicate that an exotic species may produce more than the native species, possibly thanks to higher survival, but it is also possible to increase production with successful population selection of the native species.     

Seasonal variation in gene expression for loblolly pines (Pinus taeda) from different geographical regions

In developing xylem, gene expression levels vary in different genotypes, at different stages of development, throughout a growing season, and in response to stresses. Commercially important characteristics such as wood-specific gravity are known to differ with seed source. For example, when grown on a common site, the specific gravity of Arkansas loblolly pine (Pinus taeda L.) trees is greater than that of Louisiana loblolly pine, and Texas loblolly pines have a greater specific gravity than loblolly pines from the Atlantic coast. A microarray analysis was performed to examine variation in gene expression among trees from different geographical sources when grown on a common site, and seasonal variation in gene expression in each seed source. We used microarrays containing 2171 expressed sequence tags (ESTs) with putative functions of interest, selected from several loblolly pine xylem partial cDNA libraries and a shoot tip library. Genes with significant variation in expression for each factor were identified. Many genes preferentially expressed in latewood compared with earlywood were for proteins involved in cell wall biosynthesis. Variation in gene expression among trees from the two seed sources in each growing season suggests that there may be more differences between South Arkansas trees and South Louisiana trees in latewood than in earlywood. Variation in gene expression among trees from different regions may reflect adaptation to different environments.     

Genotype × environment interactions in selected loblolly and slash pine plantations in the Southeastern United States

Few studies have quantified the combined effects of silvicultural treatments and genetic improvement on unit area production of full-sib family blocks of loblolly (Pinus taeda L.) and slash pine (P. elliottii Engelm. var. elliotttii). Efficient operational deployment of genetic materials requires an understanding of possible site and silvicultural treatment interactions to maximize yield potential. We examined genotype (family) by environmental interactions (G × E) through age 5 years using a factorial experiment consisting of silvicultural treatment intensity (operational versus intensive), planting density (1334 versus 2990 trees ha⁻¹) and families (seven elite full-sib loblolly and six elite full-sib slash pine families). In January of 2000, randomized complete block, split-plot experiments were installed at two locations for each species in southeast Georgia and northeast Florida. Five years after planting, both loblolly and slash pine demonstrated significant interactions among several factors: genotype × location (p < 0.028 and p < 0.016, respectively), genotype × silvicultural treatment intensity (p < 0.055 and p < 0.059), and silvicultural treatment intensity × density (p < 0.002 and p < 0.001) for basal area (BA) and standing stem volume (VOL). Genotype × silvicultural treatment interactions were positive, with the best overall performing families responding the greatest to intensive treatment. There were changes in slash pine family rankings between locations, which were partly explained by reductions in growth associated with a combination of fusiform rust infection [Cronartium quercum (Berk.) Miyabe ex Shirai f. sp. fusiforme] and wind damage from the 2004 hurricane season. No three-way interactions, which included family, were evident and all genetic sources were stable across the contrasting planting densities. At age 5, loblolly pine outperformed slash pine (p < 0.0001), especially under the intensive silvicultural intensity. While loblolly performance was similar whether deployed in mixtures or pure family blocks, slash pine tended to be more productive in intimate mixtures than when grown in pure family blocks (p = 0.0754 for aboveground biomass).     

14年生火炬松优良家系选择

在福建省漳平五一国有林场,对美国引进的火炬松第1代种子园25个家系试验林进行测定,以湿地松、马尾松为对照。结果表明:火炬松早期生长较易感染松针褐斑病,保存率较低;14年生火炬松家系总体生长优于湿地松、低于马尾松;各家系在树高、胸径和材积等性状上有着显著差异;综合各性状共选择出4个优良家系(21、9、18、13号),14年生树高、胸径和单株材积的平均值分别为12.6 m、20.4 cm、0.1981 m3,比湿地松增长9.2%、25.9%、71.1%,遗传增益达8.9%、24.7%、67.9%。     

Genetic transformation of loblolly pine using mature zygotic embryo expiants byAgrobacterium tumefaciens

Agrobacterium tumefaciens strain LBA 4404 carrying pBI121 plasmid was used to transform mature zygotic embryos of three genotypes (E-Hb, E-Ma, and E-Mc) of loblolly pine. The results demonstrated that the expression frequency of β-glucuronidase reporter gene (GUS) varied among genotypes after mature zygotic embryos were infected withAgrobacterium tumefaciens cultures. The highest frequency (27.8%) of GUS expressing embryos was obtained from genotype E-Mc with mean number of 21.9 blue GUS spots per embryo. Expression of β-glucuronidase reporter gene was observed on cotyledons, hypocotyls, and radicles of transformed mature zygotic embryos, as well as on organogenic callus and regenerated shoots derived from co-cultivated mature zygotic embryos. Nineteen regenerated transgenic plants were obtained from GUS expression and kanamycin resistant calli. The presence and integration of the GUS gene was confirmed by polymerase chain reaction (PCR) and Southern blot analysis. These results suggested that an efficientAgrobacterium 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 the future studies on transferring economically important genes to loblolly pine.     

Carbonic anhydrase in Tectona grandis: kinetics, stability, isozyme analysis and relationship with photosynthesis

Carbonic anhydrase (CA, EC: 4.2.1.1) activity in teak (Tectona grandis L.f.) was studied to determine its characteristics, kinetics and isozyme patterns. We also investigated effects of leaf age, plant age and genotype on CA activity and gas exchange parameters. Carbonic anhydrase extracted from leaves in 12 mM veronal buffer, pH 7.8, had a K(m) for CO(2) of 15.20 mM and a V(max) of 35,448 U mg(-1) chlorophyll min(-1), which values declined by 50 and 70%, respectively, after 1 week of storage at 4 degrees C. A 15% native polyacrylamide gel revealed the absence of CA isozymes in teak, with only a single CA band of 45 kD molecular mass observed across 10 segregating half-sib families and groups of trees ranging in age from 10 to 25 years. Activity remained stable during the first month in storage at 0 degrees C, but gradually declined to 25% of the initial value after 1 year in storage. During the period of active growth (February-May), maximal CA activity was observed in fully expanded and illuminated leaves. Significant variation was observed in CA activity across 10 1-year-old half-sib families and 21 5-year-old half-sib families. There was a positive correlation between CA activity and photosynthetic rate in a population of 10-year-old trees (P < 0.005). Positive correlations between CA activity and photosynthetic rate were found in 10 of 21 5-year-old half-sib families (P < 0.005 to P < 0.05), which showed greater diversity in CA activity than in photosynthetic characteristics. Thus, CA may serve as a biochemical marker for photosynthetic capacity in teak genotypes.     

Genetic variation in rooting ability of loblolly pine cuttings: effects of auxin and family on rooting by hypocotyl cuttings

After about 20 days, hypocotyl cuttings from 20-day-old loblolly pine (Pinus taeda L.) seedlings rooted easily in the presence of the auxin indole-3-butyric acid (IBA), with roots forming directly from xylem parenchyma. In contrast, woody cuttings from 1-2-year-old hedged seedlings formed roots indirectly from callus tissue in 60-90 days, but IBA had little effect on rooting. Variation in rooting among hypocotyls from both half- and full-sib families was highly significant in response to IBA, and rooting did not occur within 20 days unless IBA was applied. Hypocotyls from poor rooting families tended to produce fewer roots per cutting than hypocotyls from good rooting families. Rooting by woody cuttings and hypocotyl cuttings from the same nine full-sib families was weakly correlated, raising the possibility that at least some common genetically controlled processes were affecting rooting by both types of cutting. The phytotropin N-1-naphthylphthalamic acid (NPA), supplied at 1 micro M with 10 micro M IBA, significantly inhibited rooting by hypocotyl cuttings from both good and poor rooting families, but there was no significant family x treatment interaction. Family variation in rooting ability may be a function of the frequency of occurrence of auxin-responsive cells in the hypocotyls.     

Loblolly pine and slash pine responses to acute aluminum and acid exposures

In response to concerns about aluminum and HCl exposure associated with rocket motor testing and launches, survival and growth of full-sib families of loblolly pine (Pinus taeda L.) and slash pine (Pinus elliottii Engelm.) were evaluated in a nursery bed experiment. Each species was exposed to a single soil application of aluminum chloride (0.33 M AlCl(3), pH 2.5), hydrochloric acid (0.39 M HCl, pH 0.6) or water, with or without mycorrhizal inoculation with Pisolithus tinctorius (Coker and Couch). After 20 weeks without inoculation, survival in AlCl(3) and HCl treatments averaged 52% for loblolly pine and 72% for slash pine. Inoculation improved survival of loblolly pine, receiving HCl from 49 to 73%, and of those receiving AlCl3, from 55 to 90%. Inoculation also resulted in improved survival and growth of individual families in AlCl(3), but not in HCl treatments. Results illustrate the relative resistance of both pine species to the acute treatments supplied, the improvement in resistance associated with mycorrhizal inoculation and the importance of field testing, following hydroponic screening, to verify the resistance to soil-supplied stresses.     

Leaf traits in relation to crown development, light interception and growth of elite families of loblolly and slash pine

Crown architecture and size influence leaf area distribution within tree crowns and have large effects on the light environment in forest canopies. The use of selected genotypes in combination with silvicultural treatments that optimize site conditions in forest plantations provide both a challenge and an opportunity to study the biological and environmental determinants of forest growth. We investigated tree growth, crown development and leaf traits of two elite families of loblolly pine (Pinus taeda L.) and one family of slash pine (P. elliottii Mill.) at canopy closure. Two contrasting silvicultural treatments -- repeated fertilization and control of competing vegetation (MI treatment), and a single fertilization and control of competing vegetation treatment (C treatment) -- were applied at two experimental sites in the West Gulf Coastal Plain in Texas and Louisiana. At a common tree size (diameter at breast height), loblolly pine trees had longer and wider crowns, and at the plot-level, intercepted a greater fraction of photosynthetic photon flux than slash pine trees. Leaf-level, light-saturated assimilation rates (A(max)) and both mass- and area-based leaf nitrogen (N) decreased, and specific leaf area (SLA) increased with increasing canopy depth. Leaf-trait gradients were steeper in crowns of loblolly pine trees than of slash pine trees for SLA and leaf N, but not for A(max). There were no species differences in A(max), except in mass-based photosynthesis in upper crowns, but the effect of silvicultural treatment on A(max) differed between sites. Across all crown positions, A(max) was correlated with leaf N, but the relationship differed between sites and treatments. Observed patterns of variation in leaf properties within crowns reflected acclimation to developing light gradients in stands with closing canopies. Tree growth was not directly related to A(max), but there was a strong correlation between tree growth and plot-level light interception in both species. Growth efficiency was unaffected by silvicultural treatment. Thus, when coupled with leaf area and light interception at the crown and canopy levels, A(max) provides insight into family and silvicultural effects on tree growth.     

Accentuation of gas exchange gradients in flushes of ponderosa pine exposed to ozone

Two-year-old ponderosa pine seedlings (Pinus ponderosa Laws.) were exposed to episodic O(3) concentrations in open-top chambers for two consecutive growing seasons (June through September of 1990 and 1991). Near the end of the second season of O(3) exposure, gas exchange was measured on needles of surviving flushes at saturating CO(2) and photosynthetic photon flux density (PPFD). Both photosynthetic capacity (A(sat)) and stomatal conductance to water vapor (g(wv)) declined linearly with needle age but differences within a flush were also found. Gas exchange rates of needles from the base of the current-year flush were significantly lower than those of needles from the top of the flush, even though age differences between needles were negligible. Although most measurements were conducted at saturating CO(2), similar patterns of gas exchange were also found at 350 micro mol mol(-1) CO(2), indicating that photosynthesis of needles at the bottom of the flush was more strongly affected by O(3) than that of needles at the top of the flush, even though the potential for O(3) uptake was probably less in needles at the bottom of the flush because of reduced stomatal conductance. Carboxylation efficiency (deltaA/deltaC(i)), the linear slope of the A/C(i) response, was highly correlated with A(sat), varying with needle age, needle position in the flush and O(3) exposure, but the magnitude of the reductions was greater than for A(sat). We conclude that susceptibility to O(3) damage among needles of an individual seedling varies not only with needle age but also with needle position, and that reductions in photosynthetic capacity may not be directly attributable to increased uptake of the pollutant. The data also indicate the need to consider within-flush variation when estimating whole-plant carbon gain and O(3) uptake.     

黧蒴栲半同胞家系生长性状变异规律及遗传参数估算

为探讨黧蒴栲半同胞家系生长性状遗传变异规律和估测其遗传参数,采用完全随机区组设计,对52个6年生黧蒴栲半同胞家系进行生长测定分析。结果表明：黧蒴栲家系间胸径、树高和材积生长均存在极显著差异。52个黧蒴栲半同胞家系平均胸径为8.53em,变异幅度为6.31～10.85am;平均树高为8.23m,变异幅度为5.08～10.14m;平均材积为0.02828 m^3,变异幅度为0.01099～0.05407 m^3。黧蒴栲半同胞家系胸径遗传变异系数为13.74％、广义遗传力为0.7404;树高遗传变异系数为13.74％,广义遗传力为0.7150;材积遗传变异系数为35.36％,广义遗传力为0.7539。表明黧蒴栲半同胞家系胸径、树高变异较小,受较强遗传控制,材积变异较大,也受较强遗传控制,通过一定强度的选择,能获得较高的遗传增益。