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Genotypic variation and horticultural potential of Alnus maritima [Marsh.] Nutt. (seaside alder), a large shrub or small tree found naturally in only three small, disjunct populations, have not been studied. We examined effects of population of origin and environment on seed germination and the growth and morphology of seedlings. Our first germination experiment showed that 6 weeks of cold stratification applied to half-siblings from Oklahoma optimized germination at 73.2%. When this treatment was applied to multiple half-sib seed sources from all populations in a second experiment, seeds from Oklahoma had a higher germination percentage (55%) than seeds from both Georgia (31.4%) and the Delmarva Peninsula (14.7%). A third experiment showed that growth of seedlings increased with increasing irradiance intensity up to 258 μmol·m–2·s–1, and survival and growth of seedlings from Oklahoma varied with root media. In a fourth experiment, multiple groups of half-siblings from all three populations were grown in one environment to compare variation in growth and morphology within and among populations. Leaves of Oklahoma seedlings were longer (12.8 cm) and more narrow (2.15 length: width ratio) than leaves of seedlings from Georgia (12.0 cm long, ratio = 1.76) and the Delmarva Peninsula (11.6 cm long, ratio = 1.86). Seedlings from Oklahoma and Georgia had a higher growth rate (180.7 and 160.0 mg/day, respectively) than did seedlings from Delmarva (130.1 mg/day), while Oklahoma and Delmarva seedlings were more densely foliated (0.72 and 0.64 leaves and lateral shoots per cm of primary stem, respectively) than those from Georgia (0.46 per cm). These differences indicate both divergence among the three disjunct populations and potential to exploit genetic variation to select horticulturally superior A. maritima for use in managed landscapes.

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Alnus maritima (Marsh.) Nutt. (seaside alder) is a rare, woody-plant species with potential for use in managed landscapes. Information on the propagation and production of this species is not available. Our objective was to evaluate the use of softwood cuttings to propagate A. maritima, with emphasis on how indole-3-butyric acid (IBA), plant provenance, and time of collection affect cutting survival, rooting percentage, the number of roots produced, and their length. Propagation trials were conducted with cuttings from seven trees on the Delmarva Peninsula (Eastern Shore of Maryland and southern Delaware) and seven trees in Oklahoma. Cuttings from mature plants in both provenances were collected on 14 June and 23 Aug. 1998; wounded; treated with IBA at 0, 1, or 8 g·kg-1; and placed under intermittent mist in a greenhouse for 9 weeks. Use of IBA at 8 g·kg-1 caused a greater rooting percentage (68%), root count (7.2), and root length (39.2 mm) than did the other IBA rates when applied to cuttings from Oklahoma in June, but IBA had little effect on cuttings from the Delmarva Peninsula. Across IBA treatments, rooting of cuttings from Oklahoma (55% in June and 12% in August) was greater than the rooting of cuttings from Delmarva (27% in June and 3% in August). Cuttings from Oklahoma had greater survival, callus development, root length, and root count than did cuttings from the Delmarva Peninsula during June and August trials. Averaged over IBA treatments and provenances, cuttings collected on 14 June rooted more frequently (41%) than did cuttings collected 23 Aug. (8%). We conclude that softwood cuttings from mature plants are an effective way to multiply clones of A. maritima, particularly when cuttings are collected early in the season and treated with IBA at 8 g·kg-1.

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Desiccation damage in ornamental plant species is of particular concern to the nursery and landscape industry. Species in two genera, Acer and Alnus, display fundamental differences in how drought affects leaves. The same soil moisture content that causes foliar desiccation and abscission in Alnus maritima (Marsh.) Nutt. (seaside alder) causes neither response in Acer rubrum L. (red maple). Understanding molecular mechanisms associated with plant response to drought stress can be an im portant factor in developing strategies for improved sustainability in urban landscapes. Our objective was to characterize expression of drought-induced dehydrin genes in leaves of `Red Sunset' red maple (desiccation-resistant) and seaside alder (desiccation-sensitive) in response to dehydration and rehydration. Potted cuttings grown in a glasshouse were subjected to four cycles of drought and rehydration. Stomatal conductance and volumetric moisture content of rooting medium were used to determine when drought cycles ended. During the second and fourth cycles, leaves were sampled for RNA and protein extraction. Dehydrin probes were generated from genomic DNA of both species by using PCR with primers designed from conserved regions in dehydrin genes. Southern blot analyses revealed the presence of dehydrin genes in seaside alder and red maple genomes. Reverse transcriptase (RT)-PCR was used to isolate desiccation-induced dehydrin cDNAs from total RNA extracted from drought-stressed leaves. The cDNA clones show 61% to 66% identity at the nucleic acid level with dehydrin genes of soybean, sunflower, radish, and potato. Accumulation of dehydrin transcripts and proteins in leaves in response to dehydration and rehydration are being studied through northern and western blot analyses, respectively. Our results may lead to a rapid screening technique for seedlings with improved mechanisms of drought resistance.

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Alnus maritima [Marsh.] Nutt. (seaside alder) is a rare, North American species with strong potential for use in managed landscapes. Information on the propagation and production of this species is not available. Our objective was to evaluate the potential for using softwood cuttings to propagate A. maritima, with emphasis on how IBA and plant provenance affect rooting success. Propagation trials were conducted with cuttings from seven trees native to the Delmarva Peninsula and seven trees from Oklahoma. Cuttings from both provenances were collected on 14 June and 23 Aug. Cuttings were wounded; treated with 0, 1, or 8 g/kg IBA; and placed under intermittent mist in a greenhouse for 9 weeks. The highest percentage of rooting (67.9) was achieved for the Oklahoma provenance by using 8 g/kg IBA in June. Across IBA treatments, rooting of cuttings from Oklahoma, 54.8% (June) and 12.4% (August), was higher than rooting of cuttings from Delmarva, 27.1% (June) and 3.1% (August). IBA at 8 g/kg caused a higher rooting percentage than the other IBA rates at both times of the season. More cuttings collected 14 June rooted (41%) than those collected 23 Aug. (7.7%) over IBA treatments. Another experiment involved cuttings from one juvenile, greenhouse-grown seedling from Oklahoma that showed 100% rooting with both 1 and 8 g/kg IBA. Shoot growth appeared more vigorous on rooted cuttings from these juvenile stems than on plants derived by rooting mature tissue collected in nature. We conclude that using softwood cuttings can be an effective way to multiply clones of A. maritima, particularly when stock plants are juvenile and cuttings are treated with IBA.

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Traits associated with drought resistance vary with provenance of hard maples (Acer sp.), but the stability of differences ex situ and over time is unknown. We compared growth, dry-matter partitioning, leaf anatomy, and water relations of seedlings from central Iowa, eastern Iowa, and the northeastern United States over 2 years. Some seedlings from each of the three provenances were used as well-irrigated controls. The remaining seedlings were drought-stressed and irrigated based on evapotranspiration. Across irrigation treatments, plants from Iowa had shorter stems and higher specific weight of lamina, root: shoot dry-weight ratios, and root: lamina dry-weight ratios than did plants from the northeastern United States when treatments began. Biomass partitioning did not differ based on provenance after irrigation treatment for 2 years, but leaves from central Iowa had a higher specific weight, and their abaxial surfaces had more stomates and trichomes, than did leaves from the Northeast. Drought stress reduced conductance only in plants from central Iowa. Across provenances, drought stress reduced stomatal frequency, surface area of laminae, and dry weights of laminae and roots, and increased root: shoot dry-weight ratio. Leaf water potential of plants subjected to drought was lower at predawn and higher at midday than that of control plants. Drought did not cause osmotic adjustment in leaves. We conclude that the stability of foliar differences among provenances of hard maples validates using these traits as criteria for selecting ecotypes for use in managed landscapes prone to drought.

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Use of subirrigation to root stem cuttings was compared to using mist, and effects of fertilization during subirrigation were determined. All cuttings of Dendranthema ×grandiflorum (Ramat.) Kitamura `Charm' and Coleus ×hybridus Voss. rooted, but misted D. ×grandiflorum `Charm' had a higher mean root mass than subirrigated cuttings. Percentage rooting and mean root mass of subirrigated Acer rubrum L. `Franksred' were 95% and 321 mg, whereas mean root mass of the 21% of cuttings that rooted with mist was 38 mg. Percentage cuttings with callus, mean callus diameter, rooting percentage, and mean root mass of Syringa retuculata (Blume) Hara were 77%, 124 mm, 21%, and 52 mg with subirrigation and 45%, 63 mm, 0%, and 0 mm with mist. Subirrigation with <7 mol N/m3 improved rooting of Impatiens hawkeri Bull. `Celebration Bright Scarlet' and A. rubrum `Franksred'. Subirrigation can replace mist, and effects of fertilizer in subirrigation solution vary among taxa.

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Amur maackia (Maackia amurensis Rupr. & Maxim.) is a nodulating leguminous tree with potential for increased use in cities and in the dry, cold climates of the upper Midwest and Great Plains of North America. There has been little research on nutritional requirements and production methods of this species. We determined the effect of growth medium and form of applied N on seedling growth. Amur maackia attained 3.3-times more dry mass in a medium of 5 peat: 3 perlite: 2 soil (by volume) and in coarse 1 vermiculite: 1 coarse perlite (v/v) than in three soil-less mixes that contained large proportions of composted bark. When seedlings were grown in an aerated nutrient solution, dry mass after 5 weeks was similar regardless of whether \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} , \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} , or a combination of these was supplied. But, leaf N content was 1.3-times greater in plants grown in a solution that contained at least 50% \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} compared to plants provided with all \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{-}\) \end{document} . Plants grown in solution with 750 μm N had 1.8-times more dry mass than those grown in solution with 3.75 μm N. Seedlings grown for 70 days in 5 peat: 3 perlite: 2 soil (by volume) attained the greatest dry mass when fertilized with Excel all purpose fertilizer that contained N at 10.8 mol·m–3, or with a nutrient solution that contained N at a 1.5 μm, at least half of which was \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} . For container-grown Amur maackia, we recommend using a soil-based medium and providing N as either all \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} or as a mixture of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NH}_{4}^{+}\) \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{NO}_{3}^{{\bar{{\cdot}}}}\) \end{document} .

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Its more westerly native range and apparent xeromorphic foliar traits have led to speculation that black maple (Acer nigrum Michx.f.) is more drought resistant than sugar maple (Acer saccharum Marsh.). We examined differences in morphology and anatomy of leaves of trees of these species indigenous near the 43°N latitude in the midwestern and eastern United States. Leaves were collected during July, Aug., and Sept. 1995, from 10 trees in each of 24 sites at longitudes of 71°W in Maine to 94°W in Iowa. Density of trichomes on abaxial surfaces and lamina surface area showed quadratic relationships with longitude and were greatest for leaves from westerly sites in Iowa. The percentage of total lamina surface area partitioned in the two most basipetal lobes increased linearly with longitude. Abaxial surfaces had 6 to 960 trichomes/cm2, lamina surface area was 28 to 176 cm2, and surface area partitioned in basipetal lobes was 5% to 9%. A quadratic regression function related increases in trichome density to decreasing mean annual rainfall at collection sites. Specific leaf mass ranged from 3.5 to 7.6 mg·cm–2 and did not relate to longitude. Scanning electron microscopy showed leaves throughout the range had similar trichome morphology, and light microscopy is being used to examine variation in leaf anatomy and stomatal traits.

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Hydroponic culture of tree seedlings is commonly used to study root biology; however, we have found that species differ in their responses to this practice. Responses of 2-week-old seedlings of Amur maackia (Maackia amurensis Rupr. & Maxim.) and black locust (Robinia pseudoacacia L.) to 1%, 5%, 10%, 25%, 50%, and 100% Hoagland solution #1 were determined over 5 weeks. Dry mass of black locust increased with increasing solution concentration up to 50%. For Amur maackia, dry mass was highest in 5% solution, and dry mass declined by ≈50% in 50% solution. Purpling, chlorosis, and necrosis occurred on leaves of Amur maackia in solutions ≥10%, and symptom severity increased with solution strength. Amur maackia leaf ion content increased dramatically with increasing solution strength; for instance, leaf P content increased 688% as solution strength increased from 5% to 50%. No symptoms occurred on Amur maackia grown in a soil-based medium and irrigated with 50% solution. These data indicate that black locust can be grown hydroponically using standard methods. However, growth of Amur maackia is inhibited at high solution concentrations, suggesting a sensitivity to the availability of ions, and perhaps an enhanced ability to sequester ions from its media.

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Tolerance of shade, flooding, drought, and nutrient-poor substrate is desirable among ornamental plants installed in managed landscapes. Many attractive native taxa have not been evaluated for their resistance to environmental stressors. We assessed Florida corkwood (Leitneria floridana Chapman) in its natural habitat in four disjunct populations in the United States and tested the physical and chemical properties of the soil at the study sites. Measures at all sites were made within two weeks in late June, 2003. Leaf area, plant height, length of new shoots, and the rate of photosynthesis were higher among plants receiving more than 600 μmol·m-2·s-1 of photosynthetically active radiation (PAR) compared to plants that occurred where maximum PAR was lower. Soil texture ranged from clay loam to fine sand, and soil pH across sites was 4.5 to 6.6. Concentration of nitrate-nitrogen, phosphorus, and potassium ranged from 3 to 75 mg·L-1, 7 to 11 mg·L-1, and 3 to 64 mg·L-1, respectively. Bases of plants in Florida were submersed in water, while soil moisture percentages in Missouri and Texas were 6 to 30. The apparent tolerance of L. floridana to shade, low and high soil moisture, and nutrient-poor soil in native habitats indicates that it could be used in a wide range of managed landscapes. Its capacity to adapt to shade may permit the use of L. floridana as an understory species in managed landscapes, but stewards of natural areas may need to maintain open sites within its native habitat to allow expansion of populations. Because this assessment of L. floridana included native populations across the natural range of the species, our results are uniquely suited for both horticultural and ecological interpretation and application.

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