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Martin P.n. Gent - One of the best experts on this subject based on the ideXlab platform.
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Persistence of triazole growth retardants on stem elongation of Rhododendron and Kalmia
Journal of Plant Growth Regulation, 1997Co-Authors: Martin P.n. GentAbstract:Triazole growth retardant chemicals may inhibit stem elongation of woody ornamental species for several years after application. Potted plants of large-leaf Rhododendron catawbiense and Kalmia latifolia were treated with a single spray application of paclobutrazol or uniconazole in the 2nd year from propagation. They were transplanted into the field the next spring. The elongation of stems was measured in the year of application and in the next 2–4 years. Treatments with a wide range of doses were applied in 1991, 1992, or 1995. For all except the most dilute applications, stem elongation was retarded in the year after application. At the highest doses, stem growth was inhibited for 2 years after application. The results were fit to a model of growth regulator action which assumed that stem elongation was inversely related to the amount of growth regulator applied. For paclobutrazol, the dose per plant that inhibited stem elongation half as much as a saturating dose was tenfold that for uniconazole, about 0.5 and 0.05 mg, respectively. For both chemicals, the dose-response coefficient decreased exponentially with time after application, with an exponential time constant of about 2 year−1. A dose of growth regulator which reduced stem elongation by half immediately after application would only inhibit 12% of stem elongation the next year. However, a tenfold greater dose would result in less than half the stem elongation of untreated plants in the next year.
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Long-term Effects of Triazol Growth Regulators on Stem Elongation of Rhododendron and Kalmia
HortScience, 1997Co-Authors: Martin P.n. GentAbstract:The persistence of effects of paclobutrazol or uniconazol on stem elongation was determined for several years after large-leaf Rhododendron and Kalmia latifolia were treated with a single-spray application of these triazol growth-regulator chemicals. Potted plants were treated in the second year from propagation, and transplanted into the field in the following spring. The elongation of stems was measured in the year of application and in the following 2 to 4 years. Treatments with a wide range of doses were applied in 1991, 1992, or 1995. For all except the most-dilute applications, stem elongation was retarded in the year following application. At the highest doses, stem growth was inhibited 2 years following application. The results could be explained by a model of growth regulator action that assumed stem elongation was inversely related to amount of growth regulator applied. The dose response coefficient for paclobutrazol was less than that for uniconazol. The dose that inhibited stem elongation one-half as much as a saturating dose was about 0.5 and 0.05 mg/plant, for paclobutrazol and uniconazol, respectively. The dose response coefficient decreased exponentially with time after application, with an exponential time constant of about 2/year. The model predicted a dose of growth regulator that inhibited 0.9 of stem elongation immediately after application would continue to inhibit 0.5 of stem elongation in the following year.
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Paclobutrazol or uniconazol applied early in the previous season promotes flowering of field-grown Rhododendron and Kalmia
Journal of Plant Growth Regulation, 1995Co-Authors: Martin P.n. GentAbstract:Field-grown large leaf Rhododendron and Kalmia latifolia were treated with one of three concentrations of paclobutrazol or uniconazol in April, June, or August in the second year from propagation. The elongation of stems was measured as was the number of flower buds initiated. Spray applications in April or June increased flowering at the lowest concentrations tested; 4 mg · L−1 paclobutrazol and 1.5 mg · L−1 uniconazol. Flowering was induced in cultivars that normally did not flower, and the number of flower buds per plant was increased in cultivars that normally flowered. All treatments that induced flowering also reduced stem elongation. Spray application in August failed to enhance flowering. At the concentrations tested, uniconazol was more effective than paclobutrazol in increasing the number of flower buds and reducing stem elongation of Rhododendron. For Kalmia, there was less response to the concentration of growth retardant, and the two chemicals enhanced flowering equally.
Kevin L. Griffin - One of the best experts on this subject based on the ideXlab platform.
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Leaf phenology and seasonal variation of photosynthesis of invasive Berberis thunbergii (Japanese barberry) and two co-occurring native understory shrubs in a northeastern United States deciduous forest
Oecologia, 2007Co-Authors: Kevin L. Griffin, W. S. F. SchusterAbstract:Early leafing and extended leaf longevity can be important mechanisms for the invasion of the forest understory. We compared the leaf phenology and photosynthetic characteristics of Berberis thunbergii , an early leafing invasive shrub, and two co-occurring native species, evergreen Kalmia latifolia and late leafing Vaccinium corymbosum , throughout the 2004 growing season. Berberis thunbergii leafed out 1 month earlier than V. corymbosum and approximately 2 weeks prior to the overstory trees. The photosynthetic capacity [characterized by the maximum carboxylation rate of Rubisco ( V _cmax) and the RuBP regeneration capacity mediated by the maximum electron transport rate ( J _max)] of B. thunbergii was highest in the spring open canopy, and declined with canopy closure. The 2003 overwintering leaves of K. latifolia displayed high V _cmax and J _max in spring 2004. In new leaves of K. latifolia produced in 2004, the photosynthetic capacity gradually increased to a peak in mid-September, and reduced in late November. V. corymbosum , by contrast, maintained low V _cmax and J _max throughout the growing season. In B. thunbergii , light acclimation was mediated by adjustment in both leaf mass per unit area and leaf N on a mass basis, but this adjustment was weaker or absent in K. latifolia and V. corymbosum . These results indicated that B. thunbergii utilized high irradiance in the spring while K. latifolia took advantage of high irradiance in the fall and the following spring. By contrast, V. corymbosum generally did not experience a high irradiance environment and was adapted to the low irradiance understory. The apparent success of B. thunbergii therefore, appeared related to a high spring C subsidy and subsequent acclimation to varying irradiance through active N reallocation and leaf morphological modifications.
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Seasonal variation of temperature response of respiration in invasive Berberis thunbergii (Japanese barberry) and two co-occurring native understory shrubs in a northeastern US deciduous forest
Oecologia, 2007Co-Authors: Cheng-yuan Xu, W. S. F. Schuster, Kevin L. GriffinAbstract:In the understory of a closed forest, plant growth is limited by light availability, and early leafing is proposed to be an important mechanism of plant invasion by providing a spring C “subsidy” when high light is available. However, studies on respiration, another important process determining plant net C gain, are rare in understory invasive plants. In this study, leaf properties and the temperature response of leaf respiration were compared between invasive Berberis thunbergii , an early leafing understory shrub, and two native shrubs, Kalmia latifolia , a broadleaf evergreen and Vaccinium corymbosum , a late-leafing deciduous species, in an oak-dominated deciduous forest. The seasonal trend of the basal respiration rates ( R _0) and the temperature response coefficient ( E _0), were different among the three shrubs and species-specific negative correlations were observed between R _0 and E _0. All three shrubs showed significant correlation between respiration rate on an area basis (20°C) and leaf N on an area basis. The relationship was attributed to the variation of both leaf N on a mass basis and leaf mass per area (LMA) in B. thunbergii , but to LMA only in K. latifolia and V. corymbosum . After modeling leaf respiration throughout 2004, B. thunbergii displayed much higher annual leaf respiration (mass based) than the two native shrubs, indicating a higher cost per unit of biomass investment. Thus, respiratory properties alone were not likely to lead to C balance advantage of B. thunbergii . Future studies on whole plant C budgets and leaf construction cost are needed to address the C balance advantage in early leafing understory shrubs like B. thunbergii .
W. S. F. Schuster - One of the best experts on this subject based on the ideXlab platform.
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Leaf phenology and seasonal variation of photosynthesis of invasive Berberis thunbergii (Japanese barberry) and two co-occurring native understory shrubs in a northeastern United States deciduous forest
Oecologia, 2007Co-Authors: Kevin L. Griffin, W. S. F. SchusterAbstract:Early leafing and extended leaf longevity can be important mechanisms for the invasion of the forest understory. We compared the leaf phenology and photosynthetic characteristics of Berberis thunbergii , an early leafing invasive shrub, and two co-occurring native species, evergreen Kalmia latifolia and late leafing Vaccinium corymbosum , throughout the 2004 growing season. Berberis thunbergii leafed out 1 month earlier than V. corymbosum and approximately 2 weeks prior to the overstory trees. The photosynthetic capacity [characterized by the maximum carboxylation rate of Rubisco ( V _cmax) and the RuBP regeneration capacity mediated by the maximum electron transport rate ( J _max)] of B. thunbergii was highest in the spring open canopy, and declined with canopy closure. The 2003 overwintering leaves of K. latifolia displayed high V _cmax and J _max in spring 2004. In new leaves of K. latifolia produced in 2004, the photosynthetic capacity gradually increased to a peak in mid-September, and reduced in late November. V. corymbosum , by contrast, maintained low V _cmax and J _max throughout the growing season. In B. thunbergii , light acclimation was mediated by adjustment in both leaf mass per unit area and leaf N on a mass basis, but this adjustment was weaker or absent in K. latifolia and V. corymbosum . These results indicated that B. thunbergii utilized high irradiance in the spring while K. latifolia took advantage of high irradiance in the fall and the following spring. By contrast, V. corymbosum generally did not experience a high irradiance environment and was adapted to the low irradiance understory. The apparent success of B. thunbergii therefore, appeared related to a high spring C subsidy and subsequent acclimation to varying irradiance through active N reallocation and leaf morphological modifications.
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Seasonal variation of temperature response of respiration in invasive Berberis thunbergii (Japanese barberry) and two co-occurring native understory shrubs in a northeastern US deciduous forest
Oecologia, 2007Co-Authors: Cheng-yuan Xu, W. S. F. Schuster, Kevin L. GriffinAbstract:In the understory of a closed forest, plant growth is limited by light availability, and early leafing is proposed to be an important mechanism of plant invasion by providing a spring C “subsidy” when high light is available. However, studies on respiration, another important process determining plant net C gain, are rare in understory invasive plants. In this study, leaf properties and the temperature response of leaf respiration were compared between invasive Berberis thunbergii , an early leafing understory shrub, and two native shrubs, Kalmia latifolia , a broadleaf evergreen and Vaccinium corymbosum , a late-leafing deciduous species, in an oak-dominated deciduous forest. The seasonal trend of the basal respiration rates ( R _0) and the temperature response coefficient ( E _0), were different among the three shrubs and species-specific negative correlations were observed between R _0 and E _0. All three shrubs showed significant correlation between respiration rate on an area basis (20°C) and leaf N on an area basis. The relationship was attributed to the variation of both leaf N on a mass basis and leaf mass per area (LMA) in B. thunbergii , but to LMA only in K. latifolia and V. corymbosum . After modeling leaf respiration throughout 2004, B. thunbergii displayed much higher annual leaf respiration (mass based) than the two native shrubs, indicating a higher cost per unit of biomass investment. Thus, respiratory properties alone were not likely to lead to C balance advantage of B. thunbergii . Future studies on whole plant C budgets and leaf construction cost are needed to address the C balance advantage in early leafing understory shrubs like B. thunbergii .
Paul E. Cappiello - One of the best experts on this subject based on the ideXlab platform.
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Lowest Survival Temperature (LST) Estimations in Kalmia, Viburnum, and Magnolia by Controlled Freezing
HortScience, 1997Co-Authors: John F. Wachter, Paul E. CappielloAbstract:Stems of 38 varieties of Kalmia latifolia, 33 varieties of Viburnum, and 45 varieties of Magnolia were screened for low-temperature tolerance on eight dates during the winters of 1995–96 and 1996–97. Terminal 6- to 8-cm stem cuttings were shipped overnight on ice to Orono, Maine, and processed immediately upon arrival. Cuttings were subjected to a controlled freezing regime with a lowest test temperature ranging from –31°C to –42°C. Following freezing, stems were incubated for 5 to 14 days at 21°C and evaluated for injury. Lowest survival temperatures (LST) for each variety were estimated as the lowest temperature at which 100% of stems were undamaged. Varieties of Viburnum dentatum, V. lantana, V. opulus, and V. trilobum were rated as consistently very cold-tolerant, with LSTs of at least –36°C on all test dates. All V. plicatum var. tomentosum varieties showed inconsistent survival and LST estimations. Midwinter LST estimates in Kalmia latifolia showed 40% of the tested varieties remained undamaged at or below –36°C. Ten percent of K. latifolia varieties tested were damaged at –24°C or warmer, with the remaining varieties having LSTs somewhere between –24°C and –40°C. Varieties of Magnolia showed inconsistent survival with LSTs estimated for only 5% of those tested. Direct comparisons by variety, test date and source will be discussed with emphasis on consistent LST estimation. Varieties of K. latifolia, Viburnum, and Magnolia best suited for use in northern landscapes will also be discussed.
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LOWEST SURVIVAL TEMPERATURE (LST) ESTIMATES FOR Kalmia latifolia (L.) AS AFFECTED BY NUCLEATION/SEEDING TREATMENTS
HortScience, 1996Co-Authors: John F. Wachter, Paul E. CappielloAbstract:Terminal stem cuttings of Kalmia latifolia were collected from wild plants (Milford, N.H.) on 12 Nov. and transported on ice to Orono, Maine, for analysis. Samples were processed as follows: 1) stems wrapped in dry cheesecloth; 2) stems wrapped in moist cheesecloth; and 3) stems seeded with crushed ice and wrapped in moist cheesecloth. Prepared samples were subjected to freezing tests to a low temperature of –36C. Following two weeks of incubation at 21C, samples were evaluated for leaf, petiole, stem, and vegetative bud damage. Evaluation of frozen samples revealed: 1) stem tissue remained undamaged to –36C; 2) leaf damage was inconsistent across all handling methods, with no clear LST estimate, and ice seedinggenerally resulted in increased tissue damage; 3) LSTs for vegetative buds and petiole bases were –18C and –15C, respectively, and both yielded definitive and consistent results across all treatments. The results indicate bud and petiole tissue to be the best to use for future studies on LST estimates in Kalmia latifolia.
David R. Mcmullin - One of the best experts on this subject based on the ideXlab platform.
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New 1,3-benzodioxin-4-ones from Synnemapestaloides ericacearum sp. nov., a biosynthetic link to remarkable compounds within the Xylariales.
PLOS ONE, 2018Co-Authors: Joey B. Tanney, Justin B. Renaud, J. David Miller, David R. McmullinAbstract:Surveys of foliar endophytes from the Acadian forest region over the past three decades have identified numerous phylogenetically diverse fungi producing natural products toxic to forest pests and diseases. The life histories of some conifer endophytes can be restricted to plant foliage or may include saprotrophic phases on other plants tissues or even alternate hosts. Considering the potentially broad host preferences of conifer endophytes we explored fungi isolated from understory species and their metabolites as part of an ongoing investigation of fungal biodiversity from the Acadian forest. We report a hitherto unidentified Xylariomycetidae species isolated from symptomatic Labrador tea (Rhododendron groenlandicum) leaves and mountain laurel (Kalmia latifolia) collected in coastal southern New Brunswick, Canada. Morphological and phylogenetic evidence demonstrated the unknown species was a novel Synnemapestaloides (Sporocadaceae) species, described here as Syn. ericacearum. A preliminary screening assay indicated that the culture filtrate extract of the new species was potently antifungal towards the biotrophic pathogen Microbotryum violaceum, warranting an investigation of its natural products. Two natural products possessing a rare 1,3-benzodioxin-4-one scaffold, synnemadoxins A-B (1-2), and their postulated precursor, synnemadiacid A (3), were characterized as new structures and assessed for antimicrobial activity. All isolated compounds elicited in vitro inhibitory antifungal activity towards M. violaceum at 2.3 μg mL-1 and moderate antibiotic activity. Further, the characterization of synnemadoxins A-B provided a perspective on the biosynthesis of some related 1,3-benzodioxin-4-ones produced by other fungi within the Xylariales.
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Synnemapestaloides ericacearum.
2018Co-Authors: Joey B. Tanney, Justin B. Renaud, David J. Miller, David R. McmullinAbstract:A, C, E. Leaf spots and acervuli on Rhododendron groenlandicum (DAOM 745782). B, D, F. Coalescing leaf spot and acervuli on Kalmia latifolia (DAOM 867445, holotype), triangular acervuli in F. G. Acervulus with intact host cuticle. H. Acervulus with ruptured host cuticle. I–K. Conidiophores and conidia, arrows denoting conidiogenous cells exhibiting obvious successive percurrent extensions. L–M. Conidia. Scale bars: G–M = 10 μm.
