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Abstract
The American elm, Ulmus americana L., has proven itself to be particularly well adapted to urban environments. Unfortunately, Dutch elm disease, caused by the fungus Ceratocystis ulmi (Buism.) C. Moreau, has limited use of this species. The ‘Pioneer’ hybrid elm is a product of a USDA program to develop disease resistant elm clones which can be planted as substitutes for American elm.
Abstract
The ‘Homestead’ elm is a new disease resistant cultivar developed at the USD A Nursery Crops Research Laboratory in Delaware, Ohio. It shows promise for planting as a street, highway, or landscape tree.
A recycling nutriculture system was redesigned to improve growth and flowering of Tagetes erecta L., cv., Inca Yellow in four media; loose rockwool (RW), coal bottom ash (CBA), pinewood peelings (PWP) and CBA:PWP (1:1, v/v). Three nutricycle frequencies of 12, 6 and 4 per 12 hour light period were set with a nutricycle duration of 5 minutes. Volume, height and fresh and dry weights of marigolds in CBA, PWP and CBA: PWP were comparable to that of marigolds in RW. Flower diameters of plants in CBA, PWP and CBA:PWP were increased and days to harvest decreased compared to plants in RW. Plants in CBA: PWP increased in fresh weight compared to CBA or PWP plants. No interaction occurred between media and nutricycle frequency at 12 or 4 cycles per 12 hours; however a malfunctioning timer caused prolonged flooding of plant root zones at the 6 cycle setting. This resulted in decreased plant volume and fresh and dry weights at this frequency. These results show that growth and flowering of marigolds in CBA and PWP comparable with that in RW can be achieved with more than 1 nutricycle frequency.
Freeman maples (Ace×freemanii E. Murray) are marketed as stress-resistant alternatives to red maples (Acer rubrum L.). Our objective was to compare two cultivars of Freeman maple [`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 and water deficit on plant growth, biomass partitioning, stomatal conductance, and leaf osmotic potential. Plants grown from rooted cuttings in containers were subjected to three consecutive cycles during which root-zone water content decreased to 0.12, 0.08, and 0.02 m3·m–3, respectively. Additional plants were flooded for 75 days, while plants in a control treatment were irrigated frequently. Stomatal conductance immediately before imposing drought and after three drought cycles did not differ among genotypes and averaged 220 and 26 mmol·s–1·m–2, respectively. Differences in stomatal conductance after recovery from the first drought cycle and at the end of the second drought cycle did not vary with species. Drought reduced estimated leaf osmotic potential similarly for all genotypes; means for drought-stressed and control plants were –1.92 and –1.16 MPa, respectively. Freeman maples had a higher mean root: shoot weight ratio and a lower leaf surface area: root dryweight ratio than did red maples. Across genotypes, stomatal conductance of flooded plants initially increased by ≈20% and then fell to and remained below 50 mmol·s–1·m–2. Stomatal conductance of `Indian Summer' decreased to ≈20 mmol·s–1·m–2 after 8 days of flooding, indicating that this cultivar may be particularly sensitive to root-zone saturation.
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.
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.
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.
`Inca Yellow' marigolds (Tagetes erects L.) were planted in polyethylene bags containing coal bottom ash (CBA), pine wood peelings (PWP), a mixture of 1 CBA: 1 PWP (v/v), and loose Grodan rockwool (RW) and grown in a circulating nutriculture system. Three fertigation frequencies of 12, 6, or 4 cycles per 12-hour light period were set with a duration of 5 minutes each. Flower diameters of marigolds grown in CBA, PWP, and CBA-PWP exceeded flower diameters of RW-grown marigolds, and days from planting to harvest were less in CBA and CBA-PWP than in the other two media. There was no interaction between medium and fertigation frequency. Foliar analysis showed no significant differences in plant elemental composition among root media or fertigation frequencies. Postharvest PWP water extracts contained higher P levels than extracts of other media, and CBA-PWP water extracts contained higher K, Ca, and Mg. In the CBA-PWP mixture, decomposition products from PWP may have increased P volubility and solubilized the K, Ca,-and Mg-in CBA.