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Jesse R. Quarrels and Steven E. Newman

A leaching frame was constructed to detect residual plant growth regulators in media. The table was 0.9 × 1.8 m and designed to hold 40 10-cm diameter by 30-cm PVC cylinders. Each cylinder was cut lengthwise in half and resealed with duct tape. Rooted cuttings of `Freedom' poinsettias were planted into each cylinder using two media combinations: 2 vermiculite: 2 peat moss: 1 pine bark and 2 vermiculite: 1 peat moss: 2 pine bark (by volume). Four growth regulator treatments were applied to the medium two weeks after transplanting: control, 0.25 mg paclobutrazol, 0.25 mg uniconazole, and 0.125 mg paclobutrazol applied as spike. After plant growth was recorded, the cylinders were removed and sliced lengthwise. Snapdragon plugs were then transplanted into the medium along the length of the cylinder to determine if any residual paclobutrazol remained. Paclobutrazol and uniconazole reduced stem length. The presence of pine bark in the media reduced the effect of the plant growth regulators.

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Jesse R. Quarrels and Paul G. Thompson

An experiment was conducted to determine the rate and frequency of irrigation needed for optimum yield in sweetpotato (Ipomoea batatas (L.)Lam). A line source irrigation system was used to provide continuously increasing amounts of water at each irrigation. The physiological responses of sweetpotato to water application were measured. There was an increase in leaf water potential with increasing rates of irrigation. Leaf diffusive resistance decreased as total water rate increased to 76% of pan evaporation (Epan) and then increased with higher rates of irrigation. Marketable yields increased as total water rate increased to 76% of Epan and then decreased rapidly with higher irrigation rates. Water relations measurements indicated that reduction in yield with higher amounts of water application was due to low soil oxygen content.

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Jesse R. Quarrels and Steven E. Newman

Greenhouse studies of cut flower snapdragons (Antirrhinum majus L.) using two night air and two root-zone temperatures were conducted to determine the effects on growth and quality of four cultivars in two response groups [`Cheyenne' and `Rainier White' (group II) and `Tampico' and `Potomac' (group III)]. The group II cultivars were the earliest to harvest, but at the expense of quality. Grades of first, extra, and fancy only were harvested. Group III cultivars were harvested with all grades; first, extra, fancy and special. Group II cultivars generally had weaker stems and were of lower dry weight. Night air temperature had the greatest effect on days to harvest. Harvest date was reduced more than 14 days, but at the expense of quality and dry weight. Root-zone heating decreased quality of the group II cultivars at either night air temperature. but reduced quality of the group Ill cultivars only at high night temperatures. Root-zone heat and high night air temperature reduced the number of days to harvest, also at the expense of quality. The majority of high quality stems were from group Ill cultivars harvested from rooms with low night temperatures without root-zone heat.

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Steven E. Newman and Jesse R. Quarrels

Many nurseries are using the pot-in-pot (PNP) system to grow trees in containers. This system protects the roots from temperature extremes and prevents tipping. PNP is not without problems, trees with vigorous roots may escape the container and root into the external soil making harvest difficult. PNP has no effect on root circling. Our objective was to determine if a polypropylene fabric disk treated with either trifluralin or copper placed in the bottom of a container would prevent root circling. Cercis canadensis and Quercus shumardii seedlings were grown in 19 liter polyethylene containers with eight root control treatments, which included trifluralin or copper impregnated polypropylene fabric disks placed in the bottom of the containers. Ttifluralin treatments, BioBarrier and trifluralin impregnated fabric, had few roots in the bottom of the containers. Of the copper treatments, Spinout® impregnated fabric was the only copper treatment that had any effect on root development in the bottom of the containers.

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Steven E. Newman' and Jesse R. Quarrels

The objective of this study was to determine the influence of uniconazole and calcium applied as a drench or foliar spray to `Gutbier V-14 Glory' poinsettias'. Uniconazole was drenched into half of the plants at 6 mg/pot. Calcium was applied weekly as either a spray, drench, or a combination of both at 350 ppm Ca. Uniconazole reduced plant height, bract dry weight, and plant dry weight. Bract dry weight from plants not treated with uniconazole and received calcium as a spray was less than from those plants that received either no supplemental calcium or calcium as a drench. Calcium improved the appearance of plants treated with uniconazole.

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Steven E. Newman and Jesse R. Quarrels

The objective of this study was to determine the influences of 8 commercial media, 4 peat-based and 4 pine bark-based, on the effects of uniconazole applied as a media drench to `Gutbier V-14 Glory' poinsettias. The peat-based media were Baccto Grower's Mix, Baccto High Porosity Professional, Baccto High Porosity Professional with Bacctite, and Baccto Rockwool Mix. The pine bark-based media were Metro 300, 360, 500, and 700. Uniconazole was applied to plants grown in each media at 5 rates (0, 2, 4, 6, and 8 mg · 15 cm por1).

Uniconazole effectively reduced plant height and width, bract dry weight, and bract number in all media. Plants grown in the Metro products, however, tended to be larger than those grown in the Baccto products. Bract size and number, plant weight, width and height were greatest in Metro 360. The rockwool mix produced the smallest plants. Plants grown in the peat-based media were more sensitive to uniconazole drenches. Plants grown in Metro 360 were the least sensitive to uniconazole drenches.

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Jesse R Quarrels and Steven E. Newman

A study was conducted to determine the effects of pine bark grind size and pine bark levels on the activity of two growth regulators on poinsettia Two bark grinds (≤ 6 mm and >10 mm) were used with four media combinations within each grind: vermiculite:bark:peat moss at 2:0:3, 2:1:2, 2:2:1, and 2:3:0 (by volume). Two growth regulators, paclobutrazol and uniconazole, were applied at 0, 0.125, and 0.250 mg/15 cm container in 250 ml water. Two poinsettia cultivars, `Freedom' and `Gutbier V-14 Glory', were planted September 2, 1993, pinched September 16, and growth regulators applied September 30. There were five single plant replications for each treatment. Stem length and bract area were effected by bark grind, bark level, growth regulator, and growth regulator rate. Plants treated with uniconazole had the shortest stems and the least bract area. Plants grown in the smaller grind and at higher bark levels were less effected. Plants treated with paclobutrazol had longer stems than those treated with uniconazole.

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Julia L. Lamb, Jesse R. Quarrels, and Steven E. Newman

Kenaf (Hibiscus cannabinus L.) is a member of the Malvaceae family cultivated primarily for its bast fibers. The objective of this study was to evaluate kenaf fiber core as a substitute for vermiculite in a sphagnum peat moss-based medium. Rooted cuttings of Dendranthema x grandiflora were planted into 1 liter pots containing six sphagnum peat moss-based media modified with fine or coarse, fresh or aged kenaf core and/or vermiculite. The media were (by volume): 5 peat: 5 vermiculite: 0 kenaf, 5 peat: 4 vermiculite-1 kenaf; 5 peat: 3 vermiculite: 2 kenaf; 5 peat: 2 vermiculite: 3 kenaf; 5 peat-1 vermiculite: 4 kenaf; and 5 peat: 0 vermiculite: 5 kenaf, Dolomite was added at five rates 0, 1.5, 3, 4.5, and 6 kg/m3. Gypsum was added to each medium combination to provide equal calcium levels for all treatments. The medium with no kenaf grew the tallest plants. Kenaf that was aged and finely ground produced plants similar in height to controls. Fresh kenaf was detrimental to plant growth. Dolomite ameliorated the fresh kenaf effect slightly.

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Steven E. Newman, Jesse R. Quarrels, Jacobo Cáceres, and William E. Batson

Poinsettia growers generally apply fungicide drenches to circumvent any potential problems corn soil-borne pathogens. This involves a considerable expense in chemical purchase and exposes the handler to risk. A potential biological control organism in commercial production is Gliocladium virens and is being marketed under the trade name GlioGard. This fungal organism is pathogenic towards other fungi including Rhizocotonia solani and Pythium. Two cultivars of poinsettia `Freedom' and `Gutbier V-14 Glory' were planted into Metro 366 medium, half colonized with 0.9 kg·m-3 GlioGard and half not. Half of the rooted cuttings were planted at the standard depth and half planted deep (3 cm). No additional fungicide treatment was made. Those plants transplanted normally without GlioGard had 70-85% survival where those treated with GlioGard had 75-95% survival.