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  • Author or Editor: Roy A. Larson x
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Abstract

Plants of ‘May Shoesmith’ chrysanthemum (Chrysanthemum morifolium Ramat.) were grown in controlled environment chambers at optimal (16°C) and sup-optimal night temperatures. Reduced night temperatures were imposed for all or part of the night cycle. Number of days to flowering was delayed as night temperature decreased from 16° or as duration of reduced temperature during each diurnal cycle was increased. Compared to plants grown at a continuous 16° night temperature, plants grown at 10° for 9 or 10½ hours each night (with the remaining hours at 16°) had greater stem diameter, were taller and had flowers with greater diameter and fresh weight. Number of nodes was not affected.

Open Access

Abstract

‘Paul Richter’ tulips were forced in controlled environment chambers at 26/22, 22/18, and 18/14°C day/night temperatures using high and reduced light intensity and short and long daylengths. Photoperiod had no influence on growth or flowering. Reduced light intensity with the coolest temperature treatment significantly increased the forcing period. Increased forcing temperatures had the greatest impact on plant growth, resulting in reduced Plant flower length, and forcing period. In a second experiment, ‘Paul Richter’ was forced in controlled environment chambers under 8 combinations of day/night temperatures from 18 to 26° day and from 14 to 22° night. The warmer day or night temperatures decreased the forcing period. Plant height was increased with increasing day temperatures, but decreased with increasing night temperature. Flower length decreased with increasing day or night temperatures. First internode length was increased with increasing day temperature but decreased with increasing night temperature, with the exception of a slight increase at a day temperature of 18°. Last internode length was increased only slightly with increasing night temperature. Flower longevity and total length were decreased slightly by increased forcing temperatures.

Open Access

Abstract

Influence of temperature, media and concentration of ancymidol (α-cyclopropyl-α-[p-methoxyphenyl]-5-pyrimidine-methanol) on the growth and flowering of selected cultivars of Chrysanthemum morifolium were studied. As day/night temperature increased or decreased from 22/18°C length of time required for the plants to come into flower increased. Stem elongation and leaf area decreased while fresh weight increased as temperatures decreased from 30/26° to 18/14°. Ancymidol applied at a concentration of 0.25 mg/pot of aqueous drench was sufficient to control height of plants grown in most media except pine bark humus. Incorporation of river sand, greenhouse soil or Ca(OH)2 into pine bark humus increased ancymidol's effectiveness. Increasing growth regulator concentration also resulted in adequate height control for plants grown in pine bark humus.

Open Access

Abstract

α-Cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol) applied to inherently tall-growing chrysanthemum cultivars controlled ht at concn of 62 mg/liter (0.06 mg/15 cm pot) when applied as a foliar spray, and 0.12 mg/15 cm pot when applied as a soil drench. An thesis was delayed in plants treated with high concn of the growth retardant but flower size and no., and node no. were unaffected.

Open Access

Dikegulac, dikegulac + GA4+7, BA, and Promalin (GA4+7 + BA) were evaluated as lateral shoot-inducing agents on greenhouse forcing azalea, Rhododendron cultivars Gloria and Prize. The addition of GA4+7 (1000 or 2000 mg.L-1) to a commercial rate of dikegulac (3900 mg.L-1) did not effectively increase plant diameter or leaf width compared to plants sprayed with dikegulac alone. The combination of dikegulac and GA4+7 (3900 + 2000 mg.L-1, respectively) was more phytotoxic than dikegulac alone. Foliar sprays of BA and Promalin at 1000 and 2000 mg.L-1 and 1000 and 1816 mg.L-1, respectively, did not increase lateral shoot count. Neither the addition of GA4+7 to dikegulac nor the use of Promalin is a viable alternative to dikegulac application for inducing lateral branch development of dikegulac-sensitive cultivars. Chemical names used: Na 2,3:4,6-Bis-0-(l-methylethylidene)-α-L-xylo-2-hexulofuranosonic acid (dikegulac), (lα,2β,4aα,4bβ,10β)-2,4a,7-trihydroxy-l-methyl-8-methylenegibb-3-ene-l,10-dicarboxylic acid l,4a-lactone (GA4+7),N-(phenylmethyl)-lH-purin-6-amine (BA), and Promalin [1:1 (wt/wt) GA4+7 and BA].

Free access

Abstract

Dormant budded plants of ‘Gloria’ azaleas (Rhododendron obtusum, Planch) and ‘Merritt Supreme’ hydrangeas [Hydrangea macrophylla (Thunb.) Ser.], and vegetative summer stock of ‘Gloria’ azaleas, were treated with various rates of chlorimuron, imazaquin, oxyfluorfen, and chloramben. Chlorimuron minimally injured both greenhouse crop species, but 0.14 kg a.i./ha was necessary to provide >70% preemergence control of the broadleaf weed species in peat-based or bark-based soilless media. Large crabgrass [Digitaria sanquinalis (L.) Scop.], redroot pigweed (Amaranthus retroflexus L.), Pennsylvania bittercress (Cardamine pensylvanica Muhl. ex. Willd.), common chickweed [Stellaria media (L.) Vill.], yellow woodsorrel (Oxalis stricta L.), and creeping woodsorrel (Oxalis corniculata L.) were the weed species tested. Imazaquin provided excellent control of all weed species at 0.56 kg a.i./ha for 14 weeks, but was phytotoxic to vegetative azaleas in both growing media. No difference in damage was detected when applications were made immediately after repotting and pinching or after 1 month of growth. Oxyfluorfen provided excellent control of all weed species for 4 weeks at 2.2 kg a.i./ha and, on all species except chickweed, for 14 weeks at 4.5 kg a.i./ha with no phytotoxicity to azaleas or hydrangeas for media drench applications. Chloramben drench and foliar spray applications at 6.7 kg a.i./ha injured vegetative azaleas regardless of application time. Foliar and drench applications of chloramben at 3.4 kg a.i./ha produced slight to moderate injury on vegetative azaleas. More injury resulted when applications were delayed until 4 weeks after pinching. Chloramben was not toxic to either dormant-budded species. Chemical names used: 2-((4[4-chloro-6-methoxypyrimidine-2yl)amino carbonvl]amino sulfonyl))benzoic acid, ethyl ester (chlorimuron); 2-[4,5-dihydro-4-methyl-4-(1-methyl-ethyl)-5-oxo-1H-imidazol-2yl]-3-quinolinecarboxylic acid (imazaquin); (2-chIoro-l-(3-ethoxy-4-nitrophenoxy)-4-(trifIuoromethyl) benzene (oxyfluorfen); 3-amino-2,5-dichloro-benzoic acid (chloramben).

Open Access

Experiments were designed to determine if the combination of 6-benzyl adenine + gibberellic acid 4+7 can promote increased lateral shoots of desirable number and length on azaleas (Rhododendron simsii Planch.). The use of dikegulac-sodium with the addition of GA4+7 was also investigated to determine if GA4+7 could overcome decreased plant height and diameter caused by dikegulac application. Treatments were applied by spraying 204 ml·m-2 to pinched plants of mean diameter and mean height of 16 and 13 cm, respectively, potted in 1.3 liter plastic containers. Shoot number, plant height and plant diameter were measured 9 weeks after application for the commercially prominent cvs. `Gloria' and `Prize'. Preliminary results indicate that 2100 mg·l-1 ai BA + 2100 mg·l-1 ai GA4+7 increases number of lateral shoots. Initial results suggest the addition of 2100 mg·l-1 ai GA4+7 to 3900 mg·l-1 ai dikegulac overcomes inhibition of internodal elongation induced by dikegulac alone. Further studies will determine the effectiveness of Promalin (N-(phenylmethyl)-1H-purine-6-amine + GA4+7, 1:1) as a pinching agent on azaleas.

Free access

Experiments were designed to determine if the combination of 6-benzyl adenine + gibberellic acid 4+7 can promote increased lateral shoots of desirable number and length on azaleas (Rhododendron simsii Planch.). The use of dikegulac-sodium with the addition of GA4+7 was also investigated to determine if GA4+7 could overcome decreased plant height and diameter caused by dikegulac application. Treatments were applied by spraying 204 ml·m-2 to pinched plants of mean diameter and mean height of 16 and 13 cm, respectively, potted in 1.3 liter plastic containers. Shoot number, plant height and plant diameter were measured 9 weeks after application for the commercially prominent cvs. `Gloria' and `Prize'. Preliminary results indicate that 2100 mg·l-1 ai BA + 2100 mg·l-1 ai GA4+7 increases number of lateral shoots. Initial results suggest the addition of 2100 mg·l-1 ai GA4+7 to 3900 mg·l-1 ai dikegulac overcomes inhibition of internodal elongation induced by dikegulac alone. Further studies will determine the effectiveness of Promalin (N-(phenylmethyl)-1H-purine-6-amine + GA4+7, 1:1) as a pinching agent on azaleas.

Free access

Abstract

Moisture retention data were collected for five porous materials: soil, phenolic foam, and three combinations of commonly used media components. Two mathematical functions were evaluated for their ability to describe the water content–soil moisture relationship. A cubic polynomial function with linear parameters previously used on container media was compared to a closed-form nonlinear parameter model developed to describe water conductivity in mineral soils. In most tests for precision, adequacy, accuracy, and validation, the nonlinear function was superior to the simpler power series. The nonlinear function provides an excellent tool for describing the water content for media with widely varying physical properties.

Open Access

Abstract

Handling and preparing growing media can have pronounced effects on the “intensity variables” bulk density and equilibrium volume wetness through changes in pore size distribution. These changes in turn affect the container “capacity variables”: the absolute amounts of medium, air, and water in a container. A nonlinear moisture retention function was combined with container geometry in an equilibrium capacity variable (ECV) model that provided accurate predictions of total porosity, container capacity, air space, unavailable water, available water, and solid fraction for several container-medium combinations.

Open Access