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  • Author or Editor: Frank A. Blazich x
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Catawba rhododendron (Rhododendron catawbiense Michx.) seedlings of two provenances, Johnston County, N.C. (35°45′N, 78°12′W, elevation = 67 m), and Yancey County, N.C. (35°45′N, 82°16′W, elevation = 1954 m), were grown in controlled-environment chambers for 18 weeks with days at 18, 22, 26, or 30C in factorial combination with nights at 14, 18, 22, or 26C. Seedlings of the higher-elevation provenance generally exhibited higher net leaf photosynthetic rates (PN)s than those from the lower elevation at all temperature combinations. Thus, it appears seedlings of the high-elevation provenance possess greater relative thermotolerance, expressed as net photosynthesis, than the low-elevation provenance. Eighty-seven days after initiation (DAI) of the experiment, PN showed a quadratic response to increasing day temperature, with the maximum occurring at 22C, whereas PN decreased linearly with increasing night temperature. At 122 DAI, PN increased linearly with increasing day temperature with nights at 22 and 26C. Highest PNs were at 30/22C and 26/22C. Carbohydrate export increased with increasing day temperature, whereas the response to night temperature was minimal. High levels of nonstructural carbohydrates occurred at thermoperiods (22/22C and 26/22C) that optimize seedling growth. However, definitive trends relating seedling growth to PNs, leaf carbohydrate levels, or to the amount of carbohydrate exported from the leaves were difficult to generalize due to numerous day × night interactions.

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The length of time between transplanting and subsequent new root initiation, root growth rates, and root growth periodicity influences the ability of woody ornamentals to survive transplanting and become established in the landscape. Research was conducted to compare root growth of a difficult-to-transplant species, Kalmia latifolia L. (mountain laurel), to that of an easy-to-transplant species, Ilex crenata Thunb. (Japanese holly), over the course of 1 year. Micropropagated liners of `Sarah' mountain laurel and rooted stem cuttings of `Compacta' holly were potted in 3-L containers. Plants were grown in a greenhouse from May to September, at which time they were moved outside to a gravel pad, where they remained until the following May. Destructive plant harvests were conducted every 2 to 4 weeks for 1 year. At each harvest, leaf area, shoot dry weight (stems and leaves), root length, root area, and root dry weight were determined. Throughout the experiment, shoot dry weight and leaf area were similar for the two species. New root growth of `Compacta' holly and `Sarah' mountain laurel was measurable 15 and 30 days after potting, respectively. Root length and root area of `Sarah' mountain laurel increased during May through December but decreased during January through May. Root length and root area of `Compacta' holly increased linearly throughout the course of the experiment. Final root: shoot ratio of `Sarah' mountain laurel was one-ninth that of `Compacta' holly. Results suggest that poor transplant performance of mountain laurel in the landscape may be related to its slow rate of root growth.

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Seven concentrations of indole-3-butyric acid (IBA), seven concentrations of 1-naphthaleneacetic acid (NAA), and a nonauxin control were tested over three growth stages to determine their ability to promote adventitious rooting of stem cuttings from 3- and 4-year-old stock plants of virginia pine (Pinus virginiana Mill.). Cuttings were harvested September 2000 (semi-hardwood), February 2001 (hardwood), June 2001 (softwood), and October 2001 (semi-hardwood), treated with auxin concentrations ranging from 0 to 64 mm and placed under intermittent mist in a greenhouse. Rooting percentage, percent mortality, number of primary roots, total root length, root symmetry, root angle, and root diameter were assessed following 16 weeks. Growth stage affected every rooting trait measured except root symmetry and diameter. Auxin type affected total root length and root diameter, while auxin concentration affected every rooting trait except root angle. The highest predicted rooting percentages (46%) occurred when semi-hardwood cuttings were collected in September 2000 and treated with 7 mm auxin. Cuttings collected within the same growing season (2001) exhibited the highest predicted rooting percentage (33%) when softwood cuttings were treated with 6 mm auxin. Semi-hardwood cuttings rooted in 2001 produced the greatest number of roots and root lengths. Root diameter was significantly greater when NAA rather than IBA was applied, especially at higher concentrations.

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Seven concentrations of IBA and seven concentrations of NAA plus a nonauxin control were tested over three growth stages to determine their effectiveness in promoting adventitious root formation on stem cuttings taken from 3- and 4-year-old stock plants of Fraser fir [Abies fraseri (Pursh) Poir.]. Cuttings were prepared in March (hardwood), June (softwood), or November (semi-hardwood) 2001, treated with auxin concentrations ranging from 0 to 64 mm, and placed under mist. Rooting percentage, percent mortality, number of primary roots, total root length, root system symmetry, and root angle were recorded after 16 weeks. Growth stage and auxin concentration significantly affected every rooting trait except root angle. NAA significantly increased the number of primary roots and total root length. However, auxin type did not significantly affect rooting percentage or percent mortality. The highest rooting percentages (99%) occurred when softwood cuttings were treated with 5 mm auxin, however, semi-hardwood cuttings also rooted at high percentages (90%) and had no mortality when treated with 14 mm auxin. Regardless of auxin type, the number of primary roots and total root length varied in similar patterns across concentration, although, NAA tended to induce a greater response. To root Fraser fir stem cuttings collected from 3- and 4-year-old stock plants, it is recommended that a concentration of 5 mm NAA should be used on softwood cuttings and 14 mm IBA on semi-hardwood cuttings. Chemical names used: indole-3-butyric acid (IBA); 1-naphthaleneacetic acid (NAA).

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Eight taxa of Salvia L., representing broad geographic origin and diversity within the genus, were grown under long day conditions for 36 d at 15-h days of 20, 25, 30, 35, or 40 °C and 9-h nights of 15 or 25 °C. Taxa of European origin displayed broader tolerance to high day temperatures (DTs) with the lowest relative reduction in growth and net photosynthesis (Pn) occurring at DTs 30 °C or greater compared with those native to North and South America. Salvia splendens Sell. ex Roem. & Schult. (scarlet sage) was particularly intolerant of high temperatures with all plants dying at days of 40 °C. All plants of S. nemorosa L.‘Ostfriesland’ (‘Ostfriesland’ wood sage), S. pratensis L. (meadow sage), and S. × sylvestris L. ‘Mainacht’ (‘May Night’ salvia) survived at days of 40 °C with no visual signs of injury, whereas all other taxa except S. splendens exhibited stunted, contorted growth with foliar chlorosis and necrosis at 40 °C. Day temperature exerted the primary effect on top growth, root growth, and Pn of all taxa. Night temperature effects were significant for some taxa but were of less importance than day temperature.

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Uniconazole was applied as a foliar spray at 0, 90, 130, 170, or 210 ppm to rooted stem cuttings of `Spectabilis' forsythia (Forsythia xintermedia Zab.) potted in calcined clay. Uniconazole resulted in higher total leaf chlorophyll (chlorophyll + chlorophyll,) concentration and a decreased ratio of chlorophyll a: b. Stomata1 density of the most recently matured leaves increased linearly with increasing uniconazole concentration 40, 60, and 100 days after treatment (DAT). The number of stomata per leaf (stomata1 index) increased linearly with increasing concentration of uniconazole throughout the initial 100 DAT. Uniconazole suppressed stomata1 length at all sampling dates and the level of suppression increased with increasing concentration of uniconazole from 20 to 100 DAT. Stomata1 width was suppressed by uniconazole at 40 DAT. Leaves developed after uniconazole application had higher levels of net photosynthesis when measured 55, 77, and 365 DAT. Stomata1 conductance for uniconazole-treated plants was higher compared to nontreated control (0 mg·liter-1) plants when measured 49, 55, 77, and 365 DAT. Initiation of secondary xylem for stem tissues of uniconazole-treated plants was suppressed and expansion of xylem vessel length and width was less. Secondary phloem tissues of stems from uniconazole-treated plants contained larger numbers of phloem fibers having smaller cross sectional areas than phloem fibers of controls. Chemical name used: (E)-1-(p-Chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-01 (uniconazole).

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Containerized seedlings of eastern redcedar (Juniperus virginiana L.) were fertilized weekly for 175 days with a solution containing 50 ppm P, 150 ppm K, and either 0, 5, 10, 20, 40, 80, 160, 320, or 640 ppm N. Plant height, stem diameter, and shoot and root dry weights increased asymptotically with applied N; 640 ppm N diminished response. Growth after 175 (height, stem diameter) and 180 (shoot and root dry weights) days was optimal (90% of maximum) at N concentrations of 115, 155, 230, and 105 ppm, respectively, 1.5% foliar N optimized height growth. Foliar concentrations of N, P, and K increased in treated plants over the duration of the experiment, while Ca, Mg, and Mn decreased or remained constant. Starch concentration of fertilized plants decreased sharply after initiation of the experiment, but controls showed little change during the first 120 days. Sucrose concentration remained constant over the summer but increased sharply in late fall. At 180 days, foliar concentrations of starch, sucrose, hexose, N, P, K, and B increased asymptotically with applied N; concentrations of Ca, Mg, and Mn decreased.

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