Browsing by Author "Barry Goldfarb, Committee Co-Chair"

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Adventitious Rooting and Physiology of Stem Cuttings of Loblolly Pine
(2005-04-13) LeBude, Anthony Vincent; Farrell C. Wise, Committee Member; Barry Goldfarb, Committee Co-Chair; John Frampton, Committee Member; Frank A. Blazich, Committee Co-Chair
Vegetative propagation by stem cuttings can be used to multiply improved seedlings of timber species before deployment for reforestation. Before full scale deployment of rooted stem cuttings can be accomplished on an operational level, however, various obstacles need to be overcome. Among these obstacles are development of rooted cutting production systems and effective control of the rooting environment to stimulate adventitious root formation. Therefore, two separate series of experiments were conducted to develop protocols for clonal propagation of loblolly pine (Pinus taeda L.) by stem cuttings. The first series of experiments were conducted to test the efficacy of two containerized production systems on rooting percentage, root system morphology, and first year field growth of rooted stem cuttings of loblolly pine. The second series of experiments focused on the effect of the rooting environment on adventitious root formation to define a propagation protocol with broad application that stimulates rooting among several rooting environments. In the first series of experiments, three studies were conducted to test adventitious rooting of juvenile hardwood (dormant) or softwood (succulent) stem cuttings of six unrelated full-sib families of loblolly pine in various sizes of Jiffy® Forestry Peat Pellets or Ray Leach Conetainers™ and the subsequent effect on first year field growth after outplanting. Controls in all experiments were Ray Leach Super Cells filled with a medium of 2 peat : 3 perlite (v/v). After adventitious rooting in the greenhouse and 12 months of field growth, all plants, with the exception of plants produced in one Jiffy pellet size, were shorter than the controls and had less root dry weight (DW) and shoot DW. Results suggest that preplant root DW is an important predictor of first year field performance. Therefore, cuttings rooted in pellets may need to be transplanted to a nursery bed for further root growth and development prior to field planting. Rigid plastic containers remain a viable production system because cuttings rooted consistently, had large root mass, and plants were of commercial size after 1 year of field growth. In the second series of experiments, six studies were conducted. Four studies investigated the influence of cutting water potential (Ψcut) on rooting of juvenile dormant and succulent stem cuttings of loblolly pine propagated under varying substrate water potentials (Ψsub) and volumes of mist application (mist levels). In the first two studies, mist level and Ψsub contributed to the Ψcut of nonrooted stem cuttings. In the second two studies, when Ψsub was held constant across various mist treatments, mist level contributed strongly to Ψcut. In the first two studies, Ψsub affected rooting percentage when mist was suboptimal or excessive; otherwise, mist had a stronger effect than Ψsub on rooting percentage. For all four studies, cuttings rooted best when experiencing moderate water deficits (- 0.5 to - 1.2 MPa) during the period of adventitious root formation. Results demonstrate that monitoring the physiological status of stem cuttings during adventitious rooting can provide important information for controlling the rooting environment. The final two studies of the second series of experiments investigated the relationships between mist application, vapor pressure deficit (VPD), Ψcut, and rooting percentage of dormant or succulent stem cuttings of loblolly pine. In addition, net photosynthesis at ambient conditions (Aambient) and stomatal conductance (gs) of succulent stem cuttings were measured during adventitious root formation to determine their relationship to rooting percentage. Dormant stem cuttings rooted ≥ 80% when mean daily VPD between 1000 and 1800 HR ranged from 0.60 to 0.85 kPa. Although rooting percentage was related to Ψcut and gs, and Aambient was related to Ψcut and gs, rooting percentage of succulent stem cuttings was not related to Aambient. Using VPD as a control mechanism for mist application during adventitious rooting of stem cuttings of loblolly pine might increase rooting percentages across a variety of rooting environments.
Primary Productivity and Forage Quality of Gingko Biloba in Response to Elevated Carbon Dioxide and Oxygen - An Experimental Approach to Mid-mesozoic Paleoecology
(2006-11-15) Decherd, Sara Maurine; Dale Russell, Committee Member; Mary Schweitzer, Committee Member; Elisabeth Wheeler, Committee Member; Barry Goldfarb, Committee Co-Chair; Reese Barrick, Committee Co-Chair
Atmospheric composition was unique during the Late Jurassic and Early Cretaceous Periods (˜180-90 mya) due to concurrent elevations of CO₂ and O₂. Experimental methodology, an under-utilized technique in paleoecology, is used to address the physiological responses of Ginkgo biloba seedlings to these conditions. Experimental results have implications to Mid-Mesozoic paleoecology. Plants were exposed to these atmospheric treatments in hyperbaric chambers: Control: 1 atm pressure, 370 ppm CO₂, and 20.9% O₂ CO2: 1.25 atm pressure, 2000 ppm CO₂, and 20.9% O₂ CO2&O2: 1.25 atm pressure, 2000 ppm CO₂, and 30% O₂ Gas exchange parameters were measured after 24-Hour and 35-Day exposure to evaluate photosynthetic rate and primary productivity. G. biloba photosynthesis was stimulated by CO₂, but experienced photosynthetic down-regulation after 35 days. Elevated O₂ did not decrease photosynthetic rate. The concentrations of protein, lignin, sugar, and starch, and the C:N ratio and non-structural to structural carbohydrate ratio of experimental G. biloba leaves were measured to assess foliage quality. Nutritive content was reduced while digestibility was increased in response to elevated CO₂ and O₂. Observed changes in G. biloba suggest mid-Mesozoic primary productivity could have been increased 200-300% over control levels; plant growth rate and fecundity may have increased. Changes in foliar quality could have stimulated herbivore and detritivore biomass and affected foraging strategies during the mid-Mesozoic. Stomatal density and index values of experimental leaves were compared with gas exchange data and stomatal values from mid-Mesozoic Ginkgo fossils to determine if stomatal frequency is a proxy for photosynthesis in fossil and shed leaves. Stomatal frequency correlated with conductance but not photosynthesis. Experimental and fossil values did not compare favorably. Stomatal density and index are inappropriate proxies for photosynthetic rate. This study used experimental techniques to examine G. biloba physiological responses to atmospheric conditions that existed during the distant past. The use of experimental methods for paleoecological investigation is a powerful technique.
Production System Influences the Survival and Morphology of Rooted Stem Cuttings of Loblolly Pine (Pinus taeda L.) and Sweetgum (Liquidambar styraciflua L.)
(2006-05-15) Gocke, Matthew Harrison; Frank Blazich, Committee Member; John Frampton, Committee Member; Barry Goldfarb, Committee Co-Chair; Daniel J. Robison, Committee Co-Chair
Forest planting stock must be capable of high rates of survival and good field performance to justify the expense of reforestation efforts. Seedling grading standards have improved the quality of forest planting stock and have increased expectations for survival and field growth of out-planted forest seedlings. For many tree species, rooting stem cuttings provides an alternative means of producing planting stock to that of conventional seedling propagation. Use of rooted stem cuttings (rooted cuttings) in forestry has many potential advantages for both research and operational applications. However, to realize these benefits, it is important that high quality rooted cuttings are produced to enable field performance on par with seedlings of the same species and similar provenance. Developing specific grading standards for rooted cutting planting stock, therefore, is critical for successful field performance, and, is a topic of increasing interest for clonal forestry of particular species. Grading standards for rooted cuttings may differ from those of seedlings, because of potential biological differences and increased production costs for rooted cuttings. Furthermore, various production systems exist capable of producing high quality rooted cutting planting stock and may require individual grading standards. Loblolly pine and sweetgum, to a lesser degree, are two commonly out-planted forest tree species in the southeastern United States. Seedling grading standards exist for both species in this region. Increased interest in clonal propagation of loblolly pine and sweetgum requires development of rooted cutting grading standards to ensure high rates of survival and good field performance. Two studies conducted in 2000 and 2001 investigating rooted cutting production systems for loblolly pine and sweetgum are described in the following two chapters. The effects of a transplant, a containerized, and a direct-stick production system on morphological characteristics of loblolly pine rooted cuttings were evaluated in the first chapter. Morphological comparisons were made among the various stock types tested. In the second chapter, feasibility and morphological effect of a transplant, a containerized, and a direct-stick rooted cutting production system were evaluated for sweetgum. Semi-hardwood (SH) stem cuttings of sweetgum were tested in all three production systems with special emphasis placed on the presence of new shoot growth following rooting. Hardwood (H) stem cuttings of sweetgum were also rooted in a direct-stick system in an outdoor nursery bed to test the reported ability of this cutting type to produce new shoot growth in the same season as rooting. Rooted cutting morphology varied among clone and production system for both loblolly pine experiments. By the second loblolly pine experiment, over 90% of the rooted cuttings produced in the systems tested met acceptable seedling grading standards, including the second cycle (May sticking). Results of this study demonstrated that all three production systems evaluated were capable of producing high quality planting stock and that two full production cycles can be obtained in one growing season in the containerized and transplant systems. All four production systems evaluated in the sweetgum study produced rooted cuttings. Morphological measurements varied among these same rooted cuttings according to production system. The transplant and containerized systems produced a large number of rooted cuttings with high rates of survival and large root systems. The SH direct-stick system produced rooted cuttings with sizeable root systems, but proved more sensitive than the other systems tested. A SH direct-stick system requires a back up irrigation system and a secondary power source to be effective. The H direct-stick production system was the only system to produce rooted cuttings exhibiting substantial shoot growth during the first growing season. Some of these rooted cuttings also developed extensive root systems, but survival was low.
Variation of Wood Density Traits in Rooted Cuttings and Seedlings of Loblolly Pine
(2003-12-31) Cumbie, William Patrick; Tim Mullin, Committee Member; Barry Goldfarb, Committee Co-Chair; Ilona Peszlen, Committee Member; Bailian Li, Committee Co-Chair
Wood samples were collected from 10-year-old loblolly pine (Pinus taeda L.) rooted cuttings and seedlings from nine full-sib families resulting from a 3x3 factorial mating design. The field design consisted of two sites with six blocks per site in a randomized complete block design. In the spring of 2001, 12 mm increment cores were taken from approximately 1600 trees, and measurements of height and diameter were taken at the age of 10 ½ years. No significant differences were found between rooted cuttings and seedlings for specific gravity or growth traits, but sites significantly differed for growth traits. Significant family variation was found for both growth and specific gravity. Genetic parameters were estimated for wood specific gravity and growth traits for both seedlings and rooted cuttings. Heritabilities for specific gravity were generally high, and estimates from rooted cuttings were higher than from seedlings. Specific gravity was found to be negatively correlated with height. Clones were less variable than full-sib seedlings for specific gravity. These results suggest that gains in specific gravity could be made in breeding programs through the use of clonal testing during breeding and the deployment of superior clones. Wood strips from the increment cores were then measured using x-ray densitometry. Seedlings and rooted cuttings did not differ significantly for overall latewood density, earlywood density or latewood percentage of the whole core, but overall wood density did differ significantly based on seven growth rings. Half-sib and full-sib loblolly pine families did not display significant variation, but clones within families differed significantly in wood density, latewood density, and latewood percentage, indicating the greater potential for gains from clonal selection. Heritabilities for composite ring density traits were found to be moderate to high, indicating the potential for gains in wood density through selection of families or clones. Individual ring analysis revealed that the wood density of rings 1-4 was highly correlated with wood density through ring 7, suggesting that selection of juvenile wood density could be made at an early age.