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- Author or Editor: David W. Burger x
Nodes from field-grown coppice regrowth and mature trees of Eucalyptus sideroxylon were cultured on a modified Murashige and Skoog medium containing BAP and NAA. BAP (2-4 μm) and NAA (0.5-1.0 μm) were most effective in promoting axillary shoot proliferation from coppice and adult tissues. IBA was more effective than NAA in stimulating the formation of adventitious roots from in vitro-derived shoots. Plantlets from tissue culture were easily transferred to the greenhouse environment. Chemical names used: N6-benzylaminopurine (BAP); 1-naphthaleneacetic acid (NAA); 1H-indole-3-butanoic acid (IBA).
The temperatures of liquid volumes (10–4000 ml) were monitored with solid-state temperature probes during autoclaving cycles of an automated steam sterilizer. Accurate measurements of the time required for the liquid volumes to reach the sterilizing temperature (121°C) were made. The effects of preheating solutions to be autoclaved and enclosing materials in autoclavable plastic bags were determined. Liquid volumes between 10 and 4000 ml differed in the time required to reach 121° by 40 min. Preheating solutions before autoclaving slightly reduced the time required to reach sterilizing temperatures. Enclosing materials in autoclavable bags substantially increased the time required to reach 121°.
Comparisons were made between a commercially available, solar-activated mist control device (Weather Watcher®) and time clocks to determine their relative effectiveness, usefulness, and water-use characteristics on a greenhouse mist propagation bench. Coleus cuttings produced more roots per cutting and had greater average root lengths under Weather Watcher-controlled mist than those cuttings on a mist bench controlled by time. Paulownia cuttings produced the same number of roots under solar- or time-activated mist; however, the average root length was greater under Weather Watcher control. Mist benches controlled by the Weather Watcher used only one-third the water used by benches controlled by a time clock.
Hydroponic and aeroponic methods have been used to study the propagation and growth of plants (1, 2, 4). A combination of these two methods of liquid culture, aero-hydroponics, has been developed (3). Known as the Ein Gedi System (EGS), this aerohydroponics method incorporates the advantages (buffered nutrient capacity of hydroponics and water oxygenation of aeroponics) of both types of liquid culture. The objective of this study was to compare aero-hydroponics (EGS) and solid media for cutting propagation with and without overhead mist.
The role of N metabolism in organogenesis and growth was studied using tobacco pith callus. Callus was cultured on a solid medium containing 10 μM (1.75 mg/l) IAA and 2 μM (0.43 mg/l) kinetin for 56 days. In the growth experiment, ratios of NH4 +-N to NO3 --N (0:60, 20:40, 30:30, 40:20 and 60:0 mM) were supplied by (NH4)2 SO4 and KNO3. Callus and media were analyzed for inorganic N. Callus supported by 30:30 and 40:20 media removed the highest amounts of NH4 +-N and NO3 --N from the media and exhibited organogenesis. Final dry weight was greatest in callus supported by the 30:30 medium. In the organogenesis experiment, the transfer history of the inoculum source affected N uptake, organogenesis and growth. Inorganic N was supplied by NH4NO3 and KNO3 -. The net uptake of NH4 +-N and NO3 --N was lower in shoot-forming than in root-forming and non-organogenic callus subculture from 7-day-old stock cultures. The final pH of the medium supporting shoot-forming callus was lowest. Growth, on a dry weight basis, was lowest in shoot-forming callus. Callus subculture from 60-day-old stock cultures formed no shoots.
Cuttings of Ficus benjamina L. and Chrysanthemum × morifolium(Dendranthema grandiflora tzvelev.) were rooted in aero-hydroponics to study the effect of dissolved oxygen concentrations in the range of 8 mg·liter. (ambient saturation) to 0 mg·liter−1. The results of this study indicate that dissolved oxygen is essential to root formation and root growth. Woody (Ficus) and herbaceous (Chrysanthemum) cuttings responded similarly. Lowering the dissolved oxygen concentration increased the time required to form adventitious roots, reduced rooting percentages, reduced numbers of roots formed per cutting, and reduced average root lengths. Comparisons between stirred and unstirred water suggested the development of an area of depleted oxygen concentration (boundary layer) at the stem-water interface on cuttings immersed in unstirred water. Cuttings in water stirred constantly rooted sooner and formed more roots than did those in unstirred water. Maximum rooting occurred in misted (high dissolved oxygen concentrations) sections of cuttings suspended in the aero-hydroponics chambers. Chemical name used: potassium salt of lH-indole-3-butyric acid (K-IBA).
Twelve species of woody ornamentals were grown in containers in Riverside and Davis, Calif., to determine plant water use and compare crop coefficients (Kc) calculated with reference evapotranspiration (ET) from local weather stations (ETcim) or atmometers (ETatm). Water use, Kcatm, and Kccim differed by species, location, and month of the year. Raphiolepis indica (L.) Lindl., Pittosporum tobira (Thunb.) Ait., Juniperus sabina L., and Photinia ×fraseri Dress. were the highest water users in Riverside and Arctostaphylos densiflora M.S. Bak., Juniperus, Cercis occidentalis Torr., and Pittosporum used the highest amount of water in Davis, when averaged over the 20-month study period. Rhamnus californica Eschsch., Prunus ilicifolia (Nutt.) Walp., and Cercocarpus minutiflorus Abrams. were among the lowest water users in both locations. Although plant water use fluctuated considerably between individual sampling dates, the relative ranking of species water use in each location changed very little over the study period. During periods of high winds, ETcim may not provide an accurate reference for container crops. Kc values fluctuated seasonally from as much as 1 to 4.7 for high water users, while values were stable for low water users and also for Buxus microphylla japonica Rehd. & E.H. Wils., an intermediate water user. During periods of low ET, especially in fall and winter, Kc values were artificially high and failed to correspond to the plants' low water use. Kc values for low water users seem to be useful to estimate water requirements over an extended period of time, whereas general Kc values seem to have limited value for plants with high water demand and need to be modified for different growth stages and growing locations.
Seeds of Citrus sinensis (L.) Osbeck cv. Valencia obtained from trees grown in north-central California would not germinate when fruit was harvested during the early part of the season (November 1978). Seeds from November-harvested fruit stored at 3 to 4°C for 21 days germinated 100%. A similar germination response to low temperature was obtained when seeds from fruit harvested April 1980 (exposed to only 103 hours below 3 to 4°) were treated for 3 weeks at 3 to 4°. Treatment with gibberellic acid (GA3) induced about 55% germination in seeds from non-cold-treated fruit. Germination rates for seeds from cold-treated fruit were found to increase when the seeds were presoaked in GA3 or germinated at high temperature.
Fruit of ‘Ruby Red’ grapefruit (Citrus paradisi Macf.) were treated postharvest with sodium-o-phenylphenate (SOPP), benomyl, imazalil, and etaconazole and stored under ambient conditions or were treated with SOPP, imazalil, and etaconazole and stored at 12°C. Imazalil and etaconazole were as effective as benomyl under ambient conditions and were more effective than SOPP under refrigerated conditions; 85% of the stem-end-rot was caused by Phomopsis citri (Fawc).
Treeshelters were used for the nursery production of Cedrus deodara Loud. (deodar cedar), Quercus ilex L. (holly oak), and Magnolia grandiflora L. (southern magnolia) trees growing in 19-liter containers. Air temperature, relative humidity, and CO, concentration were higher inside the treeshelters than outside. Trees grown inside treeshelters were 74% to 174% taller than trees grown without shelters. Trunk caliper of Magnolia and Quercus was not affected, however, for Cedrus trees caliper was larger for trees grown without a shelter. Upon removal of the shelter, Cedrus trees were incapable of supporting their own weight. Lateral branch development was inhibited and leaf senescence was greater with Magnolia trees grown in a shelter. Quercus trees grown in shelters were ready to be transplanted into the landscape. Water use was similar for trees grown with or without shelters. Trees grown in shelters had lower root fresh weights.