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  • Author or Editor: Alden M. Townsend x
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Abstract

Variation analysis showed significant variation among red maple (Acer rubrum L.) progenies grown from seed collected throughout the species’ natural range with respect to height, diameter, autumn color, winter injury, earliness of flusing and cessation of growth. Northern progenies showed slowest growth, most reddish autumn color, earliest flushing and budset, and least winter injury. Most traits were significantly correlated with several geographic and climatic variables, and genetic and phenotypic correlations among traits indicated that multiple-trait selection could be effective.

Open Access

Abstract

Six tree species were subjected to 0, 2000, 4500, and 7000 ppm NaCl in a hydroponics system. Flowering dogwood (Cornus florida L.) and American sycamore (Platanus occidentalis L.) showed the most foliar injury, followed by pin oak (Quercus palustris Muenchh.), honeylocust (Gleditsia triacanthos L.), eastern white pine (Pinus strobus L.), and Japanese pagoda tree (Sophora japonica L.). Height growth and dry weight increase of sycamore and dogwood, and dry weight of eastern white pine were significantly reduced by salt treatment. Dry weights of pin oak, Japanese pagoda tree, and honeylocust were unaffected. Chloride generally accumulated in higher concentrations in the leaves than in the stems, whereas Na showed the opposite pattern. Concentration of Cl in the stem was better correlated with species’ sensitivity to salt than were Cl and Na in the leaves, or Na in the stem. Although stem concentrations of N, P, Mn, Fe, B, and Zn did not change significantly with salt treatment in any of the 6 species, leaf concentrations of all of these elements did change significantly in one or more species. Manganese and Cu increased with salt in the leaves or stems of several sensitive species, but stayed stable in the tolerant species. Frequency of changes in concentrations of essential elements in response to salt occurred as often in the salt-tolerant as in the salt-sensitive species.

Open Access

Abstract

Significant interspecific and intraspecific variation was demonstrated in the rate of foliar sorption of ozone at a concentration of 0.20 ppm. White oak and white birch leaves removed the largest quantities per hour on both a per-g and per-dm basis. Red maple and white ash were the least efficient; coliseum maple, sugar maple, redvein maple, Ohio buckeye, and sweetgum were intermediate in rate of ozone removal. Differences in ozone uptake also were significant among 4 seed-source progenies of red maple. A group of seedlings from Pennsylvania demonstrated higher rates of sorption than progenies from Maine, Minnesota, and Alabama. Although significant, the differences among the red maple progenies were not as great as differences in ozone uptake rate among most species. Sorption rates by white birch seedlings increased linearly with increasing ozone concentration from 0 to 0.80 ppm. Red maple seedlings showed a linear increase in sorption rate from 0 to 0.50 ppm; from 0.50 to 0.80 ppm, ozone uptake rate continued to increase with increases in concentration, but not linearly. During a continuous 8-hr fumigation at 0.20 ppm, the rate of foliar uptake of ozone by white birch seedlings decreased only 5%. Removal of ozone by red maple foliage dropped rapidly after 6 hours of continuous exposure, and after 8 hours the rate had decreased to 40% of the original rate.

Open Access

The suitability of container-grown clones of red maple, Acer rubrum L., as a host to the potato leafhopper, Empoasca fabae Harris (Homoptera: Cicadellidae), under different fertilization regimes was determined, and compared to different freeman maple cultivars (A. ×freemanii E. Murray). Three clonal selections of red maple (USNA numbers 56026, 59904, and 55410), and three freeman maple cultivars (55892 `Indian Summer', 67256 `Jeffersred' [trademark Autumn Blaze], and 55890 `Armstrong') were potted in 7.6-L containers, fertilized with either 0, 3.3, or 6.6 g/pot of calcium nitrate and used in experiments. When given a choice, female leafhoppers laid more eggs on leaves of red maple clone 56026 than on leaves of clone 59904, with oviposition linearly increasing on both clones with increases in the fertilization level applied to the trees. Yet, when female leafhoppers were confined to leaves using organza sleeve cages, oviposition increased linearly as fertilizer level increased, without a significant clonal effect. Oviposition did not differ among freeman maple cultivars, nor was it influenced by the fertilizer level applied to the freeman maple trees. Nymphs had the lowest odds of surviving to adulthood when reared on the freeman maple `Jeffersred', but highest when reared on red maple 59904. Red maple 59904 had the fastest growth rate while red maple 55410 had the slowest. Leaf initiation and expansion in red maple 56026 was significantly slower than in the other selections. Leaf development of these three red maple clones was significantly accelerated by the application of fertilizer, regardless of level. The maple selections differed in their mean amounts of foliar macronutrients and micronutrients, which related to the fertilizer level applied to trees. Unfertilized trees had the highest C to N ratio, which decreased as fertilizer level applied to trees was increased. This study showed that fertilization improved the performance of the potato leafhopper on previously nonpreferred maple selections, and that the foliar nutrient content and C to N ratio could be used as indicators of tree susceptibility to insect attack under different growing conditions.

Free access

Artificial cross-pollinations were carried out among seven species of Celtis L. (C. bungeana Blume, C. koraiensis Nakai, C. laevigata Willd., C. occidentalis L., C. reticulata Torr., C. sinensis Pers., and C. tenuifolia Nutt.) to test the potential for interspecific hybridization in Celtis breeding. AFLP profiles were used to assess the ancestry of progeny. Hybrids formed very rarely among these seven species of Celtis: only two interspecific hybrids were obtained. Self-pollination occurred occasionally in non-emasculated trees. AFLP analysis yielded false paternal markers at a very low frequency, likely due to DNA methylation differences. Plants with unexpected paternal markers were confidently distinguished from hybrids by calculating the probability of obtaining the observed number of paternal markers by chance. The study clearly demonstrated the importance of using large numbers of markers.

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A survey was conducted in the 2001 growing season to determine the leafhopper species composition, abundance, richness, diversity, and evenness among trees of three elm (Ulmus sp.) cultivars, two U.S. National Arboretum (USNA) seedling selections of U. szechuanica Fang, and two USNA seedling selections of U. bergmanniana Schneid. in a mixed stand. 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 4,523 individuals, belonging to 39 species within seven leafhopper subfamilies, were trapped. The weekly mean number of leafhoppers collected was significantly higher on traps from `Patriot', followed by `Frontier' and `Prospector', than on traps from the USNA seedling selections. Although the weekly mean species richness for `Prospector' was lower than the other two cultivars, the three cultivars had higher mean species richness than the USNA seedling selections of U. szechuanica and U. bergmanniana. Diversity among cultivars was higher than among the USNA seedling selections. Ulmus bergmanniana 68983 and U. szechuanica 68986 shared the highest percentage of species similarity, while `Frontier' and U. szechuanica 68991 were the most dissimilar. Of the species collected, Agallia quadripunctata, Empoasca fabae and Graphocephala versuta were the most abundant. The other species were mostly rare based on their low abundance. Scaphoideus luteolus, the only confirmed vector of elm yellows in North America, was found among the elm cultivars only. Yet, the Cicadellinae leafhoppers that are vectors of Xylella fastidiosa, the causal agent of bacterial leaf scorch, were found among both the cultivars and USNA seedling selections. Such data could allow for the screening and selection of elms resistant to economically important leafhoppers.

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Little is known about drought stress resistance of Freeman maples (Acer ×freemanii E. Murray), which are hybrids of red maples (A. rubrum L.) and silver maples (A. saccharinum L.). The objective of our study was to measure plant growth and leaf water relations of `D.T.R. 102' (Autumn Fantasy), `Celzam' (Celebration), and `Marmo' Freeman maples subjected to drought. Plants grown from rooted cuttings were subjected to four consecutive cycles of water deficit followed by irrigation to container capacity. Average stomatal conductance at container capacity for all cultivars was 255 mmol·s-1·m-2 in the first drought cycle and 43 mmol·s-1·m-2 during the fourth drought cycle. Predawn and midmorning leaf water potentials of droughted plants at the end of the fourth drought cycle were 1.16 and 0.82 MPa more negative than respective values for control plants. Osmotic potential of leaves at full turgor was -1.05 MPa for controls and -1.29 MPa for droughted plants, indicating an osmotic adjustment of 0.24 MPa. Root and shoot dry mass and leaf area were reduced similarly by drought for all cultivars, while Celebration exhibited the least stem elongation. `Marmo' treated with drought had the lowest root-to-shoot ratio and the greatest ratio of leaf surface area to root dry mass. Autumn Fantasy had the lowest ratio of leaf area to stem xylem diameter. Specific leaf mass of drought-stressed Autumn Fantasy was 1.89 mg·cm-2 greater than that of corresponding controls, whereas specific masses of Celebration and `Marmo' leaves were not affected by drought. Leaf thickness was similar among cultivars, but leaves of droughted plants were 9.6 μm thicker than leaves of controls. This initial characterization of responses to drought illustrates variation among Freeman maples and suggests that breeding and selection programs might produce superior genotypes for water-deficient sites in the landscape.

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We determined transpiration rate, survival, and rooting of unmisted, softwood cuttings of `Autumn Flame' red maple (Acer rubrum L.) and `Indian Summer' Freeman maple (Acer ×freemanii E. Murray). Effects of perlite at 24, 30, and 33 °C were assessed to determine whether responses of cuttings would be consistent with cultivar differences in resistance to root-zone heat previously shown with whole plants. During 7 d, cutting fresh mass increased by ≈20% at all temperatures for `Autumn Flame' red maple, but fresh mass of `Indian Summer' Freeman maple decreased by 17% and 21% at 30 and 33 °C, respectively. The percentage of cuttings of `Indian Summer' that were alive decreased over time and with increasing temperature. Transpiration rate decreased during the first half of the treatment period and then increased to ≈1.1 and 0.3 mmol·m-2·s-1 for `Autumn Flame' and `Indian Summer', respectively. Mean rooting percentages over temperatures for `Autumn Flame' and `Indian Summer' were 69 % and 16%, respectively. Mean rooting percentages at 24, 30, and 33 °C over both cultivars were 74%, 29%, and 25%, respectively. Over temperatures, mean root count per cutting was 41 and seven, and mean root dry mass per cutting was 4.9 and 0.4 mg, for `Autumn Flame' and `Indian Summer', respectively. Use of subirrigation without mist to root stem cuttings was more successful for `Autumn Flame' than for `Indian Summer'. Temperature × cultivar interactions for cutting fresh mass and the percentage of cuttings remaining alive during treatment were consistent with previous evidence that whole plants of `Autumn Flame' are more heat resistant than plants of `Indian Summer'. Mass and survival of stem cuttings during propagation in heated rooting medium may serve as tools for screening for whole-plant heat resistance among maple genotypes.

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Freeman maples (Acer × freemanii E. Murray) are marketed as stress-resistant alternatives to red maples (Acer rubrum L.), but few data from direct comparisons of these species are available. As a first step in comparing the stress resistance of red maple and Freeman maple, responses to drought were studied in Acer × freemanii `Autumn Fantasy', `Celebration', and `Marmo'. Plants grown from rooted cuttings were treated by withholding irrigation through four drought cycles of increasing severity that were separated by irrigation to container capacity. Drought reduced shoot dry mass, root dry mass, and height growth by 64%, 43%, and 79%, respectively, over all cultivars. Predawn leaf water potential was reduced by 1.16 MPa over all cultivars, and stomatal conductance data indicated water use was more conservative over all root-zone moisture contents after repeated cycles of drought. Specific mass of drought-stressed leaves increased by 25% for `Autumn Fantasy', and microscopy to determine leaf thickness and cellular anatomy is ongoing. `Autumn Fantasy' also had the lowest ratio of leaf surface area to xylem diameter, and `Autumn Fantasy' and `Celebration' had higher ratios of root to shoot mass than `Marmo'. Pressure-volume curve analysis revealed osmotic potential of drought-stressed plants at full turgor was 0.24 MPa more negative than controls, and droughted plants had a greater apoplastic water percentage than controls. Although osmotic adjustment during drought was similar among cultivars, differences in specific mass of leaves and in ratios of transpiring and conducting tissues suggest cultivars of Freeman maple vary in resistance to drought in the landscape.

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We compared two putative Freeman maples [`Jeffersred', (Autumn Blaze ®) and `Indian Summer'] and five red maples [`Franksred' (Red Sunset ®), `Autumn Flame', `PNI 0268' (October Glory®), `Fairview Flame', and unnamed selection 59904] for effects of flooding on stomatal conductance. A method for quantifying changes in leaf color that occurred on flooded plants also was developed. Potted plants grown from rooted cuttings in a greenhouse were subjected to 75 days of root-zone inundation (flood treatment) or were irrigated frequently (control treatment). Across genotypes, stomatal conductance of flooded plants initially increased by about 20% and then fell to and was sustained below 50 mmol·s–1·m–2. Stomatal conductance of flooded plants of `Indian Summer' decreased to 20 mmo·s–1·m–2 after 8 days of inundation, and two of three flooded `Indian Summer' plants died during treatment. Other genotypes required at least twice this time to display a similar reduction in stomatal conductance, indicating `Indian Summer' may be particularly flood sensitive. Intensities of red, green, and blue color at a consistent interveinal position were analyzed with Visilog software by using scanned leaf images of the youngest fully expanded leaf of each plant in both treatments. A genotype × irrigation interaction existed for the ratio of green to red intensity. This method provided numerical data that corresponded well to differences among genotypes we observed visually. For example, while flooding did not alter the color of `Autumn Flame' leaves, the ratio of green to red was three times greater for controls of Autumn Blaze® than for the flooded plants of this cultivar.

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