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- Author or Editor: Roy A. Larson x
- Journal of the American Society for Horticultural Science x
Abstract
Three gibberellins; GA3, GA4, GA7; and abscisic acid (ABA) from the shoot tips of greenhouse grown ‘Gloria’ azaleas, Rhododendron sp.L., were tentatively identified using column chromatography, gas-liquid chromatography, and Rumex leaf senesence bioassay. Growth regulators were quantitatively estimated biweekly from 6 weeks after shoot tip removal until anthesis.
GA3 levels remained nominal for the normal commercial treatment until after plants were returned to 19°C from the 9° cooler. Endogenous GA3 levels then peaked at 0.6 μg/bud at anthesis. GA4 levels remained fairly constant for all treatments and times at 0.1 μg/bud. GA7 levels remained fairly constant below 2 μg/bud except in the cold-treated plants when endogenous GA7 levels peaked at 0.6 μg/bud at the time that plants were removed from the cooler.
ABA levels were similar until 24 wks. from pinch when the levels dropped to undetectable levels in cold-treated plants and increased in treatments not given a cold treatment by peaking at 0.1 μg/bud at 28 wks. from pinch.
Of the commercially available gibberellins that were monitored, GA7 seemed to be the best treatment for chemically overcoming flower bud dormancy in azalea.
Abstract
Periodic shaking increased the resistance of potted poinsettia (Euphorbia pulcherrima Klotzsch ex. Willd., cv. Annette Hegg Diva) plants to mechanically induced leaf epinasty, but this resistance was lost within 24 hours of discontinuing the shaking. Bending petioles, not their reorientation in the gravitational field, caused increased ethylene production by excised petioles. Foliar sprays containing 40 μm cycloheximide, which were applied 24 hours before the plants were sleeved for 24 hours, completely prevented mechanically induced leaf epinasty, but were phytotoxic to the bracts.
Abstract
Flower bud development was ascertained by biweekly dissections of shoot apices, until bud color was apparent. Satisfactory results were obtained when plants were given 3 weeks at 2 or 9°C, followed by 3 applications of GA3 at 250 ppm. The results were less satisfactory when attempts were made to completely substitute GA3 for the cool temp requirement to break dormancy.
Abstract
Vegetative growth, flower bud initiation, and early flower development of ‘Red American Beauty’ azaleas were enhanced at temp of 30-26°, 26-22°, 30-22°, 26-18°, and 22-18°C. Earliest flowering occurred following temp of 22-18°, 22-14°, and 18-14°C. The 4°C difference between day and night temp resulted in plants superior in quality to those exposed to an 8° difference.
Abstract
Foliar sprays of either 10 mM aminoethoxyvinylglycine or 3 mM silver ions applied 24 hours before potted poinsettia plants (Euphorbia pulcherrima Klotzsch ex. Willd., cv. Annette Hegg Diva) were sleeved for 24 hours, significantly reduced the development of leaf epinasty after removal of the sleeves.
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.
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.
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.
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).
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.