October Glory Research Articles

Effects of Different Amounts of Codominant Stem Subordination on the Growth and Aesthetics ofAcer rubrum‘October Glory’

AbstractBackgroundCodominant stems are a common condition of concern on landscape trees. Understanding the impact of varying degrees of stem reduction can assist practitioners in making informed pruning decisions.MethodsTo determine this, a single reduction or removal cut was made on each pair of codominant stems on medium-agedAcer rubrum‘October Glory’ at approximately 25%, 50%, 75%, and 100% of the diameter relative to the basal diameter at the shared union or left as nonpruned controls. Changes in stem diameter ratio, trunk diameter growth, sprout production, wound closure, and aesthetics were documented for 4 years starting in 2020.ResultsStem diameter ratio was significantly reduced in codominant stems pruned to a relative diameter of 50% or 75% after a single growing season. The 75% treatment reduced growth for 2 growing seasons. There were no significant differences in change of stem diameter ratio with any treatment after 3 growing seasons. Larger pruning cuts resulted in the growth of more sprouts and more exposed wood after 3 years. Aesthetics of trees following pruning were acceptable for nonpruned, 25%, and 50% treatments in all years but were rated as not acceptable or moderately acceptable for 75% and 100% treatments after 2 growing seasons. Trees with the 75% treatment became aesthetically acceptable after 3 growing seasons.ConclusionsPruning codominant stems ofA. rubrum‘October Glory’ with a cut that is 50% or 75% the diameter of the basal diameter at the shared union is appropriate at reducing stem diameter ratio, minimizing exposed wood, and maintaining overall aesthetic appearance after 2 to 3 years.

Resistance of Red Maple and Freeman Maple Cultivars to Phytopythium vexans, a Causal Agent of Root and Crown Rot Disease.

Phytopythium root rot caused by Phytopythium vexans is an emerging threat to red maple and Freeman maple production that seriously impacts plant growth, aesthetic, and economic values. This study reports on the resistance of red maple and Freeman maple cultivars against root rot disease caused by P. vexans. Rooted cuttings were received from a commercial nursery and planted in 3-gallon containers. For each cultivar, six plants were inoculated by drenching 300 ml/plant of P. vexans suspension, prepared by blending two plates of 10-day-old P. vexans culture/liter sterile water. An equal number of plants remained noninoculated and were drenched with 300 ml of sterile water. Two trials were conducted for 4 months in the greenhouse during the summer of 2023. Plants were evaluated for growth, physiology, Phytopythium root rot severity (0 to 100% of roots affected), and pathogen reisolation frequency. Out of seven cultivars, Somerset had the lowest Phytopythium root rot severity and pathogen reisolation frequency. Cultivars Autumn Blaze, Brandywine, and October Glory were highly susceptible to P. vexans, whereas Sun Valley, Summer Red, and Celebration were found to have a partial resistance to P. vexans. Cultivars Autumn Blaze, Brandywine, and October Glory had significantly lower chlorophyll content, net photosynthesis, and stomatal conductance compared with the other three cultivars under pathogen inoculation. Phytopythium root rot reduced plant height, width, total plant, and root fresh weight. The disease severity was negatively correlated with width, chlorophyll content, net photosynthesis, and stomatal conductance. These results can aid growers and landscapers in developing effective P. vexans management strategies.

First Report of Bacterial Leaf Spot of Red Maple Caused by Pseudomonas syringae pv. syringae in Tennessee.

Red maple (Acer rubrum L.) is an economically important ornamental nursery plant grown for its aesthetic value. In May 2022, field and container-grown red maple 'October Glory' plants exhibited severe leaf spots in a commercial nursery in Warren Co., Tennessee. Leaf spots were brown-to-black color with a yellow halo (Fig. 1a). Disease severity was about 40% of leaf area and incidence was 60-70% of 10,000 plants. Symptomatic leaf tissues were surface sterilized with 0.525% sodium hypochlorite for 1 min and washed twice with sterilized water. Bacterial colonies, cream colored and circular with smooth margins, were obtained on King's B (KB) and nutrient agar media after 3 days of incubation at 28°C. Bacteria were gram-negative and fluorescent on KB under UV light. The biochemical and physiological test results were negative for cytochrome C oxidase, pectolytic activity on potato slices, and arginine dehydrolase, but positive for gelatin liquefaction, aesculin hydrolysis, and levan production. The BIOLOG test was positive for the utilization of D-galactose, D-galacturonic acid, D-galactonic acid lactone, D-gluconic acid, and was negative for the utilization of β-methyl-D-glucoside, N-acetyl-D-glucosamine, α-hydroxybutyric acid, D-glucose-6-phosphate, α-keto-butyric acid, and α-keto-glutaric acid. To confirm the bacterial identity, total genomic DNA was extracted using DNeasy PowerLyzer Microbial Kit directly from pure cultures (strains FBG1662 and FBG4230). The small subunit ribosomal RNA (16S rRNA), RNA polymerase sigma factor (rpoDp and rpoDs), citrate synthase (gltA), DNA gyrase (gyrB) genes were amplified and sequenced by primers 8F/1492R (Galkiewicz et al. 2008), rpoDpF/R, rpoDsF/R, gltAF/R, and gyrBF/R (Sarkar and Guttman 2004), respectively. The sequences of the two strains (GenBank accession nos. 16S: OP962145 and OP948281; rpoDp: OP998258 and OP957300; rpoDs: OP998259 and OP957299: gltA: OP998256 and OP957301; gyrB: OP998257 and OP957302) were >99% similar (100% coverage) to the complete genome of Pseudomonas syringae pv. syringae (CP026568) in the NCBI database. A phylogenetic analysis was performed and confirmed the identity using concatenated sequences of gltA, gyrB, rpoDp, rpoDs, and 16S of P. syringae pv. syringae and other closely related taxa retrieved from GenBank (Fig. 2). Based on morphological and molecular identification, both bacterial strains were identified as P. syringae pv. syringae. Pathogenicity test was conducted by spray inoculation of ten one-year-old red maple 'October Glory' with bacterial suspension (107 CFU/ml) using bacterial strain FBG4230. Ten plants were sprayed with sterilized water as control. All plants were covered with clear plastic for 24 h and incubated in a greenhouse at 21 to 23°C, 70%RH, 16-h photoperiod. At seven days after inoculation, brown-to-black leaf spots surrounded by yellow halo were developed on all inoculated plants (Fig. 1b), while the control plants remained symptomless. The bacterium was re-isolated from the inoculated plants and it was 100% identical to P. syringae pv. syringae using biochemical tests as well as sequence analysis. P. syringae has been reported pathogenic in red maple causing leaf spot in Oregon (Malvick and Moore, 1988). To our knowledge, this is the first report of bacterial leaf spot caused by P. syringae pv. syringae in red maple in Tennessee. Identification of this bacterial pathogen on red maple is crucial in developing timely management practices.

Cover crop usage for the sustainable management of soilborne diseases in woody ornamental nursery production system

Cover crops represent a potential tool for suppression of soil borne diseases in woody ornamental nursery production, which can cause significant economic losses. Field experiments were conducted in 2019 and 2020 to explore the effects of a cover crop and the timing of cover crop disturbance on soilborne disease suppression. Soils from red maple (Acer rubrum ‘October Glory’) plantations grown with or without a cover crop [crimson clover (Trifolium incarnatum)] were sampled following senescence of the cover crop. Greenhouse bioassays were conducted using red maple cuttings on inoculated (with Rhizoctonia solani, Phytopythium vexans or Phytophthora nicotianae) and non-inoculated field soils. Plant height, total and root fresh weight were measured, and the roots were assessed for disease severity on a 0 to 100% root damage scale. Pathogen recovery was assessed by culturing root pieces (~1 cm length) on oomycetes or Rhizoctonia semi-selective media. Soil samples were analyzed for organic matter, nitrogen, phosphorus, potassium, pH and Pseudomonad population count. A minimal effect of cover crop disturbance timing (late fall or early spring) was found on disease suppression. Cover crop usage reduced disease severity and pathogen recovery in red maple field soils. Plants grown in cover cropped soil had greater total, root and aboveground fresh weight compared with those from non-cover cropped soil, but plant height was not affected. Cover crops increased soil organic matter and total nitrogen in 2020. Pseudomonad populations were higher when cover crops were used. The results suggest that cover crops can reduce soilborne disease in woody ornamentals.

Species and season affect response of container-grown shade trees to pre-plant root modifications

Container-grown shade trees make up an increasing proportion of nursery stock, yet arborists and urban foresters are often concerned about root defects associated with trees grown in smooth-sided containers, such as circling roots, persisting in the landscape post-transplant. The objective of this study was to determine the effect of root modifications (shaving or bare-rooting) at planting on establishment, survival, and growth of container-grown Acer rubrum L. ‘October Glory’, Liriodendron tulipifera L. ‘Fastigiatum’, and Platanus x acerifolia (Aiton) Willd. ‘Bloodgood’. Trees were planted on two dates (May and July) in 2018 and evaluated for two growing seasons. Modifying roots before planting resulted in increased occurrence of leaf scorch for L. tulipifera and A. rubrum trees. Nearly all trees bare-rooted before planting in July had severe die-back. Survival was excellent (>75 %) for all A. rubrum and P. x acerifolia trees planted in May regardless of treatment. Survival for L. tulipifera trees that were bare-rooted in May was 50 %; all L. tulipifera trees that were bare-rooted in July died. Bare-rooting increased predawn leaf water potential (Ψw) immediately after planting. However, Ψw did not differ among root treatments for the rest of 2018 and throughout 2019. This suggests that trees with modified root systems achieved a functional equilibrium by adjusting leaf area to reduce whole-tree water loss. Root biomass outside the original root-ball did not differ among root modification treatments two years post-transplant. However, bare-rooting reduced the proportion of circling roots compared to control trees for all species. Shaving root systems reduced circling roots compared to the control for L. tulipifera and P. x acerifolia trees. For practitioners interested in trialing these techniques, we advise performing root modifications in the dormant season and avoiding species known to be difficult to transplant bareroot.

Identification and Chemical and Biological Management of Phytopythium vexans, the Causal Agent of Phytopythium Root and Crown Rot of Woody Ornamentals.

Soilborne diseases caused by pathogens such as Phytophthora, Rhizoctonia, Fusarium, Verticillium, and Pythium species are the most important diseases of woody ornamentals. Ginkgo (Ginkgo biloba) and red maple (Acer rubrum 'October Glory') plants grown in containers and fields in Tennessee showed root and crown rot symptoms with dark brown to black lesions in 2017 and 2018. The objective of this research was to isolate and identify pathogens affecting ginkgo and red maple plants in Tennessee nurseries and to develop fungicide/biofungicide management recommendations for nursery producers. Isolations were made from the infected roots. Several Phytophthora-like colonies with spherical zoospores, filamentous to globose oogoni, and whitish mycelium were isolated on V8-PARPH medium. To confirm identity, total genomic DNA was extracted, followed by sequence analysis of the internal transcribed spacer regions, large subunit of nuclear rRNA, and cytochrome c oxidase subunits I and II of mitochondrial DNA. Based on morphological and molecular analysis, Phytopythium vexans was described as a causal agent of crown and root rot from the infected ginkgo and red maple plants. To complete Koch's postulates, a pathogenicity test was performed by drenching 100 ml of V8 agar medium slurry of Phytopythium vexans inoculum on 1-year-old potted ginkgo plant root systems as well as red maple October Glory. Necrotic lesion development was observed in the root system 45 days after inoculation and Phytopythium vexans was reisolated from the roots of both ginkgo and red maple. All control ginkgo and red maple plants remained disease free and no pathogen was reisolated. In addition, the efficacy of fungicides, biofungicides, fertilizer, and host plant defense inducers (traditionally recommended for management of oomycete diseases) for control of Phytopythium crown and root rot was evaluated on ginkgo and red maple October Glory seedlings in greenhouse and field trials. Fungicides such as Empress Intrinsic, Pageant Intrinsic, Segovis, and Subdue MAXX were effective in both greenhouse and field trials, and the biofungicide Stargus reduced disease severity caused by pathogen Phytopythium vexans on ginkgo and red maple plants in greenhouse trials. These results will help nursery producers make proper management decisions for newly reported Phytopythium crown and root rot disease of ginkgo and red maple plants.

Physiological response and resistance of three cultivars of Acer rubrum L. to continuous drought stress

Red maple (Acer rubrum L.) is a fast-growing tree of medium height that is indigenous to the eastern United States and southern Canada. The tree furnishes reasonably strong, close-grained wood that is used extensively for inexpensive furniture, in the manufacture of baskets and crates, for mine props, railroad ties, and fuel wood. Many cultivars have been selected, of which almost all are selections for leaf color characteristics. In this study, three cultivars of red maple (Acer rubrum ‘October Glory’, Acer × freemanii ‘Jeffersred’, and Acer rubrum ‘Brandywine’) were selected to compare their physiological response and resistance to continuous drought stress. Before the experiment, two-year-old seedlings were grown at respective day/night temperatures of 25/18°C and 70%/80% RH without water limitation. The drought treatment was initiated by ceasing water supply until the seedlings showed visible signs of wilting. Drought is a common environmental stress that severely limits plant growth and development. Plants have evolved many mechanisms to adapt to environmental stresses via changes at the physiological, morphological, and molecular levels. In the present study, nine physiological indices, namely concentration of proline, soluble protein, and soluble sugar, activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), malondialdehyde (MDA) concentration, relative chlorophyll concentration, and relative conductivity of cell membranes, were measured to investigate the tolerance mechanism of red maple during the whole drought stress. Water deficit caused a progressive spread of tissue damage, as indicated by the physiological indices monitored, which was always observed first in the young leaves. October Glory experienced severe damage, whereas injury to Brandywine developed more slowly and was less severe, and Jeffersred showed an intermediate level of injury. A significant increase in the levels of osmoregulatory substances was observed in seedlings of all cultivars. Soluble protein and soluble sugar contents showed the same trends, namely a decrease after a rapid transient increase, whereas proline contents showed no significant changes during the drought-stress treatment. Osmoregulatory responses to drought stress of Jeffersred and Brandywine were initiated from the 6th day of treatment, whereas in October Glory responses were observed from the 13th day of treatment. October Glory showed the best osmoregulatory capability of the three cultivars. The activities of SOD and CAT initially increased, and thereafter rapidly decreased, in response to drought stress, whereas POD activity showed the opposite trend. Brandywine showed the most active antioxidant system in which activities of SOD, CAT, and POD were higher than those of the other cultivars throughout the experiment. Antioxidant activity of Jeffersred was higher than that of October Glory, in which only POD activity was maintained at a high level. Continuous drought damaged the cell membrane systems of seedlings, with gradual increases in relative membrane conductivity and MDA concentrations of cells closely associated with the duration of drought stress. Relative membrane conductivity and MDA concentration did not differ significantly between Jeffersred and Brandywine, whereas in October Glory both indices increased significantly at advanced stages of drought stress (P<0.05). Among the three cultivars, damage to the cell membrane system was most severe in October Glory over the duration of the experiment. Chlorophyll concentration decreased gradually with increasing duration of drought stress, but significant variation in response among the cultivars was observed; chlorophyll concentration was most stable in ‘Jeffersred’, whereas October Glory showed the most dramatic loss of chlorophyll and Brandywine showed an intermediate response. Chlorophyll loss with increasing duration of drought stress was consistent with the damage observed to the cell membrane system. Combining the membership function with the physiological observations for assessment of the drought resistance of the three red maple cultivars, we concluded that the relative drought stress resistance of the cultivars was Brandywine>Jeffersred>October Glory.

Carbon Footprint and Related Production Costs of Pot-in-Pot System Components for Red Maple Using Life Cycle Assessment

Component input materials and activities of a model pot-in-pot (PIP) production system were analyzed using life cycle assessment methods. The impact of each component on global warming potential (GWP; kilograms of CO2-equivalent), or carbon footprint, and variable production costs was determined for a 5 cm caliper Acer rubrum L. ‘October Glory’ in a #25 container. Total greenhouse gas emissions (GHG) of inputs and processes at the nursery gate for a defined model system were 15.317 kg CO2e. Carbon sequestration weighted over a 100-year assessment period was estimated to be 4.575 kg CO2, yielding a nursery gate GWP of 10.742 kg CO2e. The major contridbutors to the GWP at the nursery gate were the substrate, production container, the 1.8 m (6 ft), branched, bare root liner, PIP system installation, and fertilization while the liner and production container also contributed significantly to the variable costs. Input materials and labor constituted about 76 and 21% of variable costs, respectively. Unlike field production systems, equipment use in PIP production accounted for only 13% of GHG emissions and 2% of variable costs.

3种北美红枫对持续高温干旱胁迫的生理响应机制

PDF HTML阅读 XML下载 导出引用 引用提醒 3种北美红枫对持续高温干旱胁迫的生理响应机制 DOI: 10.5846/stxb201303070370 作者: 作者单位: 西南大学,西南大学,西南大学,西南大学,西南大学,西南大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目(31170546);重庆市应用开发计划项目(cstc2014yykfB80015);国家农业科技成果转化项目(2011GB23600019);西南大学生态学重点学科"211工程"建设经费资助;中央高校基本科研专项重点项目(XDJK2014B026) Physiological response mechanism of three kinds of Acer rubrum L. under continuous high temperature and drought stress Author: Affiliation: Southwest University,Southwest University,Southwest University,Southwest University,Southwest University,Southwest University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对3种北美红枫幼苗进行持续高温干旱处理,通过测定幼苗渗透调节物质含量、保护酶活性、细胞质膜差别透性、丙二醛含量及叶绿素相对含量等生理生化指标和形态特征的变化,揭示了3种北美红枫幼苗对持续高温干旱胁迫的生理适应机制.研究发现,持续高温干旱处理2 d,植物叶片中的叶绿素、可溶性蛋白含量及超氧化物歧化酶、过氧化物酶、过氧化氢酶活性均有显著下降,十月光辉和秋火焰叶片开始受到热伤害,而酒红仍然生长良好.处理4-6 d时,叶片中仅可溶性蛋白含量变化不显著,其余生理指标均有显著变化:脯氨酸含量和电导率均持续显著上升,丙二醛含量呈下降趋势,此时植物体自身的生理调节机制开始发挥作用.处理6 d后,秋火焰整株叶片枯黄,十月光辉和酒红叶片的受害指数约为70%.处理10 d时,叶片中丙二醛、脯氨酸含量和电导率均达到最大值,3种北美红枫均整株枯死.3种北美红枫对持续高温干旱环境的耐受性具有一定差异,利用隶属函数的方法对试验测定的9个生理指标进行综合评价,发现秋火焰的耐受性最差,十月光辉次之,酒红的耐受性最强,这与其受害指数的变化情况是一致的. Abstract:Red maple (Acer rubrum L.), originated in North America, is one of the Aceraceae cultivated species. Red maple has high ornamental value for its beautiful treelike and gorgeous leaf color. Recently, many scholars have done researches about it in order to make more widespread in China. However, those studies are limited to breeding cultivation technology and color change mechanisms of leaves, while the studies of red maple's physical response mechanisms to high temperature have not been reported. High temperature will affect the physiological growth of plants, and it may also influence colorful-leaf plants' leaf color expression. While most cities in southern China get high temperature in summer, the climate has largely limited the introduction of the red maple. In order to explore physiological adaptive mechanisms of the red maple to adverse environments, continuous high temperature and drought stress was applied to three kinds of red maple (Acer rubrum L.) seedlings, including October Glory, Jeffersred and Brandywine. Measurements included contents of osmoregulation substance, activity of protective enzyme, cell membrane permeability, and malonaldehyde (MDA) content and relative amount of chlorophyll in the plant leaves and seedlings morphological characters. The results showed that after two days of the treatment, chlorophyll and soluble protein contents, and superoxide dismutase (SOD), peroxide enzyme (POD) and catalase enzyme (CAT) activities of plant leaves significantly decreased respectively, and the leaves of October Glory and Jeffersred began to be damaged, while those of Brandywine were still in good condition. After four to six days, there were significant changes in the physiological indices of the three species except for the contents of soluble protein. In the meantime, the contents of proline (Pro) and conductivity were keeping increasing while the contents of MDA showed a decline tendency, indicating that the plant biological controlling mechanisms began to function. Later, all the leaves of Jeffersred turned to yellow, and the injury index of the rest two species was approximate 70% respectively. The contents of MDA and Pro, and conductivity were at maximum and all the leaves in the three species died ten days after the treatment began. The results indicated that the resistances to continuous high temperature of the three species used in the experiment were different. According to a comprehensive evaluation based on subordinate function of fuzzy mathematics, Brandywine was the best among the three species in heat-resistance, compared with a lower heat-resistance in October Glory, and the lowest resistance in Jeffersred. This result is consistent with injury index. 参考文献 相似文献 引证文献

Life cycle assessment of a field-grown red maple tree to estimate its carbon footprint components

Purpose This study analyzes the interrelated components in the production of a 5-cm caliper, field-grown, spade-dug Acer rubrum ‘October Glory’ tree in terms of their contributions to the carbon footprint, global warming potential (GWP), of this balled and burlapped product during production and its complete life cycle.

Evaluation of a Single Application of Neonicotinoid and Multi-Application Contact Insecticides for Flatheaded Borer Management in Field Grown Red Maple Cultivars

Abstract Two trials evaluated insecticides for flatheaded borer control and effect on red maple (Acer rubrum L.) cultivar growth over 4 years. Chrysobothris femorata (Olivier) was the only species reared from borer damaged maples during the study. Soil-applied systemic insecticides (acephate, imidacloprid, clothianidin, dinotefuran, and thiamethoxam) and trunk-applied contact insecticides (chlorpyrifos and bifenthrin) were tested. In the 2005 trial, a one-time drench of Allectus (imidacloprid + bifenthrin) or Discus (imidacloprid + cyfluthrin) provided 2 to 4 years of protection with ‘Autumn Flame’ and ‘Franksred’ from C. femorata. Soil-applied experimental imidacloprid tablets prevented borer damage in the third and fourth post-treatment years, but were not as effective as imidacloprid drenches in the first two years. Soil applied acephate tablets, chlorpyrifos (Dursban 4E) trunk sprays, or untreated control plants had borer damage each year, which totaled up to 41.7% damage by year 4 in ‘Autumn Flame’. Trunk diameter growth and tree canopy size was greater with Discus drench or imidacloprid tablet treatments than other treatments. In the 2006 trial, drenches of Allectus, Discus, or Safari 20SG (dinotefuran) applied in May and Discus or Arena 50WDG (clothianidin) drenches applied in March provided complete protection from C. femorata the first year in ‘Fairview Flame’, ‘Franksred’, and ‘October Glory’. Discus (March) drench provided four years of complete protection among the three cultivars, while other neonicotinoid drenches had 3.7–6.3% (Arena March), 3.7–12.5% (Arena May), 0–6.3% (Discus May), 0–10.3% (Safari), and 12.5–20.5% (Flagship) total damage. Ineffective treatments included an experimental imidacloprid gel (7.4–18.8% damage), acephate tablets (18.5–75.0%), Onyx Pro Insecticide (5.1–18.8%), Dursban 2E (11.1–31.3%), one imidacloprid tablet (15.4–43.8%), or untreated plants (32.1–41.0%). This study demonstrates a single application of some neonicotinoid treatments can provide multi-year C. femorata prevention, increased maple trunk growth, and provide borer protection superior to trunk sprays.

Exploring the importance of within-canopy spatial temperature variation on transpiration predictions

Models seldom consider the effect of leaf-level biochemical acclimation to temperature when scaling forest water use. Therefore, the dependence of transpiration on temperature acclimation was investigated at the within-crown scale in climatically contrasting genotypes of Acer rubrum L., cv. October Glory (OG) and Summer Red (SR). The effects of temperature acclimation on intracanopy gradients in transpiration over a range of realistic forest growth temperatures were also assessed by simulation. Physiological parameters were applied, with or without adjustment for temperature acclimation, to account for transpiration responses to growth temperature. Both types of parameterization were scaled up to stand transpiration (expressed per unit leaf area) with an individual tree model (MAESTRA) to assess how transpiration might be affected by spatial and temporal distributions of foliage properties. The MAESTRA model performed well, but its reproducibility was dependent on physiological parameters acclimated to daytime temperature. Concordance correlation coefficients between measured and predicted transpiration were higher (0.95 and 0.98 versus 0.87 and 0.96) when model parameters reflected acclimated growth temperature. In response to temperature increases, the southern genotype (SR) transpiration responded more than the northern (OG). Conditions of elevated long-term temperature acclimation further separate their transpiration differences. Results demonstrate the importance of accounting for leaf-level physiological adjustments that are sensitive to microclimate changes and the use of provenance-, ecotype-, and/or genotype-specific parameter sets, two components likely to improve the accuracy of site-level and ecosystem-level estimates of transpiration flux.

(141) Leaf Abscisic Acid Accumulation in Response to Substrate Water Content: Variation Among Acer rubrum L. Genotypes

Quantitative differences in leaf abscisic acid (ABAL) among four cultivars of red (Acer rubrum L.) and one Freeman maple (Acer × freemanii E. Murray) were investigated. This study tested the hypothesis that ABAL concentration can be used to compare the effects of water stress on the gas exchange response of five different maple cultivars, including four red maple genotypes, `Summer Red', `October Glory', `Autumn Flame', and `Franksred' (Red Sunset), as well as one hybridized Freeman maple genotype, `Jeffersred' (Autumn Blaze). Cloned genotypes of red and Freeman maple were subjected to two treatments: 1) irrigated daily to container capacity or 2) irrigation withheld for one drought and recovery cycle. Leaf abscisic acid concentration, gas exchange, and whole-tree sap flow measurements were conducted under both conditions. Over the course of the drought stress and recovery phase, net photosynthesis (Anet), stomatal conductance (gs), and transpiration (E) declined as ABAL and instantaneous water use efficiency (A/gs) increased. This study found that ABAL tracked gs and that stomatal responsiveness to substrate moisture deficit is likely mediated by ABA accumulation in leaf tissue. This research demonstrates a leaf-level physiological response to substrate volumetric water content that appears to depend on ABAL concentration. In addition, the evidence in this study indicates that ABAL may be used as a potential surrogate for the gs response to substrate water stress and could become part of a cultivar drought tolerance selection strategy for red and Freeman maple.

Leaf Abscisic Acid Accumulation in Response To Substrate Water Content: Linking Leaf Gas Exchange Regulation with Leaf Abscisic Acid Concentration

Quantitative differences in leaf abscisic acid (ABAL) among four cultivars of red maple (Acer rubrum L.) and one freeman maple (Acer ×freemanii E. Murray) cultivar were investigated. This study tested the hypothesis that ABAL concentration can be used to compare the effects of water stress on the gas exchange response of five different maple genotypes, including four red maple cultivars [`Summer Red', `October Glory', `Autumn Flame', and `Franksred' ('Red Sunset')] and one hybridized freeman maple cultivar ['Jeffersred' ('Autumn Blaze')]. Two-year-old cloned genotypes of red maple and freeman maple were subjected to two treatments: irrigated daily to container capacity or irrigation withheld for one drought and recovery cycle. Leaf abscisic acid concentration, gas exchange, and wholetree sap flow measurements were conducted under well-watered and drought stress conditions. Over the course of the drought stress and recovery phase, net photosynthesis (Anet), stomatal conductance (gs), and transpiration (E) declined as ABAL and instantaneous water use efficiency (A/gs) increased. Until severe water stress conditions were prominent, water use was higher in `Summer Red' as compared to `October Glory'. This study found that ABAL tracked gs and that stomatal responsiveness to substrate moisture deficit is likely mediated by ABA accumulation in leaf tissue. This research demonstrates a leaf level physiological response to substrate volumetric water content that appears to depend on ABAL concentration. In addition, the evidence in this study indicates that ABAL may be used as a potential surrogate for the gs response to substrate water stress and could become part of a cultivar drought tolerance selection strategy for red maple and freeman maple.

Diversity and abundance of leafhopper species (Homoptera: Cicadellidae) among red maple clones

A survey was conducted in the 2001 growing season to examine the leafhopper diversity and abundance among trees of 17 red maple (Acer rubrum) clones. Yellow sticky traps were used to qualify and quantify the number of aerial leafhoppers from 1 May 2001 until 4 September 2001. A total of 45 species from eight different leafhopper subfamilies, for a total of 6055 individuals, were considered in this study. The mean number of leafhoppers collected, mean species richness, diversity and evenness were significantly lower on traps of trees for ‘October Glory’ than for the other clones. Yet, none of the leafhopper species dominated the weekly samples. Species similarity among clones ranged from 56 to 90%. No two clones had complete similarity. ‘Franksred’ and trees of a controlled cross between ‘October Glory’ × ‘Autumn Flame’ shared the highest degree of species similarity, while clones from PA, USA and RI, USA were the least similar. The development of new clones did not create new pest problems, but suppressed populations of damaging pests, and maintained the diversity of low abundance species.

Genotypic Variability in Photosynthesis, Water Use, and Light Absorption among Red and Freeman Maple Cultivars in Response to Drought Stress

Cultivars of red (Acer rubrum L.) and Freeman maple (Acer ×freemanii E. Murray) are popular ornamental plants which are commonly placed in a variety of landscapes. To date, little information quantifies the capacity to tolerate and recover from drought among cultivars of red and Freeman maple. The objective of this study was to compare the effects of water stress on the physiology of five different maple cultivars of marketable size including four red maple genotypes, `Summer Red', `October Glory' (October Glory), `Autumn Flame', and `Franksred' (Red Sunset), as well as one hybridized Freeman maple genotype, `Jeffersred' (Autumn Blaze). Two-year-old cloned genotypes of red and Freeman maple were subjected to two treatments: irrigated daily to container capacity or irrigation withheld for one drought and recovery cycle. Light absorption, gas exchange, and chlorophyll fluorescence measurements were conducted under well-watered and drought stress conditions that approached 0.070 m3·m-3. Compared to well-watered conditions, drought stress conditions of 0.090 m3·m-3 had a significant main effect that reduced the amount of light absorption in four of the five genotypes. Additionally, absorption among genotypes was different under both well-watered and water stress conditions. Over the course of drought stress and a recovery phase, net photosynthesis and stomatal conductance were different among genotypes. Maximum photosystem II (PSII) efficiency of dark-adapted leaves (Fv/Fm) was lowered by the water stress condition. The efficiency of excitation capture by open PSII reaction centers (Fv`/Fm') was variable among genotypes. Photochemical quenching was higher in Autumn Blaze, October Glory, and `Summer Red' under drought conditions, which corresponded with a low degree of closure of PSII centers. Additionally, the fraction of excess excitation energy was also lower. Lastly, water deficit caused an increase in PSII efficiency in all genotypes except Autumn Blaze. This research demonstrated physiological variation among commercially available red and Freeman maple genotypes that may be selected for drought tolerance based on site moisture characteristics.

Arbuscular Mycorrhizal Assessment of Ornamental Trees Grown in Tennessee Field Soils

Mycorrhizal symbiosis, a natural association between roots and certain soil fungi, can improve growth and increase stress resistance of many nursery crops. Field soils of four middle Tennessee and two eastern Tennessee nurseries were surveyed for their mycorrhizal inoculum potential (MIP), phosphorus (P) and potassium (K) concentrations, and soil pH. Arbuscular mycorrhizal (AM) fungi, which colonized seedlings of a Sorghum bicolor trap-crop, were recovered from all soils. Tissue samples were taken from young roots of three economically important tree species grown in nursery field soils: red maple (Acer rubrum L. `October Glory'), flowering dogwood (Cornus florida L. `Cherokee Princess'), and Kwanzan cherry (Prunus serrulata Lindl. `Kwanzan'). AM fungi, regardless of soil type, soil pH, or P or K concentration, had colonized young roots of all three species. Unless interested in establishing exotic mycorrhizae, ornamental nursery producers in Tennessee do not need to supplement field soils with these beneficial fungi.

Chilling and Heat Unit Levels Affect Foliar Budbreak of Selected Red and Freeman Maple Cultivars

The effects of six levels of chilling (temp &lt;7°C) on foliar budbreak of red maple (Acer rubrum) cultivars October Glory® and 'Franksred' (Red Sunset®) and Freeman maple (A. ´ freemanii) cultivar 'Autumn Fantasy' were evaluated in a study conducted from December 14, 1999, to April 7, 2000. October Glory had a greater minimum chilling hour requirement to initiate budbreak than 'Autumn Fantasy' and 'Franksred' (Red Sunset). However, once optimal chilling had been satisfied (near 600 hours), October Glory required fewer heat units than the other cultivars to reach 20% and 25% budbreak. For example, estimates for heat units required to reach 25% budbreak for October Glory were less than half that required for 'Autumn Fantasy' and 'Franksred' following 1,200 hours of chilling. Chilling was a determining factor in foliar budbreak for all cultivars, and with all three cultivars, increasing chilling produced greater budbreak percentages and the rate at which budbreak was initiated. All cultivars required fewer heat units for budbreak as chilling increased. All cultivars required over 1,700 heat units to initiate budbreak after 200 hours of chilling, but only 780 to 970 heat units after 600 hours and between 200 and 400 following 1,000 hours of chilling. Information from this and future studies may be used to facilitate the development of models for regional planting recommendations based on the amount chilling received in a given location. Calculated r2 values indicated the models provided a good fit to the data for all cultivars.

Performance of Red Maple Selections in Southern Georgia

In 1991, a cooperative project with the U.S. National Arboretum in Washington, D.C., was initiated in Tifton, Ga. (USDA hardiness zone 8a) to evaluate red maples (Acer rubrum L.) potentially suitable for the coastal plain region of the southeastern U.S. Greatest annual height growth across all cultivars over 6 years was for `Alapaha', a seedling selection from southern Georgia with annual height growth of 35 inches (88.0 cm), and several seedling selections from northern Florida with annual height increases in excess of 33 inches (86.0 cm). Selections showing the least average annual height growth were NA-56024 and NA-57772 (`Red Rocket'). For commercially available cultivars, the most dependable for fall color in Tifton was `October Glory'®. In addition, two new selections from the National Arboretum have also shown excellent fall color—`Somerset' and `Brandywine'.

Growth Periodicity for Container-Grown Red and Freeman Maple Cultivars in AHS Heat-Zone 8

Abstract Growth patterns of seven red maple (Acer rubrum L.) and three Freeman maple (Acer x freemanii E. Murray) cultivars grown in containers in Alabama were evaluated using monthly destructive harvests. The effectiveness of a growth modeling technique not previously described is demonstrated using the data presented for both the Freeman maple (red maple xsilver maple interspecific cross) and red maple categories. Freeman maple cultivars ‘Armstrong’, ‘Celzam’ (Celebration™), and ‘Jeffersred’ (Autumn Blaze™); and red maple cultivars ‘Autumn Flame’, ‘Fairview Flame’, ‘Landsburg’ (Firedance™), ‘Franksred’ (Red Sunset™), ‘Olson’ (Northfire™), ‘Northwood’, and ‘October Glory®’ were studied. Uniform liners of each cultivar were planted in 9.1-liter (#3) containers in March 1996. More than 75% of seasonal height and diameter growth was complete for most cultivars before mid-August, while only 25% of root growth had occurred by the end of August. The remaining 75% of root growth occurred from August through November. The greatest overall growth (based on height, diameter, and root growth increase) was for ‘Autumn Flame’ and ‘October Glory®’, both red maple cultivars; and Freeman maple cultivars ‘Celzam’ and ‘Jeffersred’. The least overall growth (based on height, diameter, and root growth increase), was for red maple cultivars ‘Northwood’ and ‘Landsburg’.