Seedlings of Anigozanthos manglesii D. Don responded positively to watering and fertilization when the night temperature was 12° to I5°C; at higher temperatures, these factors caused seedling death. Cold treatment (10°C for 17 hours a day for a month) of seedlings prior to planting stimulated growth, new fan production, and flower yield. Temperatures below 10° promoted flower differentiation, whereas cultivation at higher temperatures reduced flower yield. Illuminating plants at night from 2200 to 0200 HR did not affect flower yield when plants were grown at relatively low temperatures, but it did reduce yields when they were grown in a heated greenhouse.
Powdery mildew in euonymus (Euonymus japonica Thunh.) plants, caused by Oidium euonymi-japonica (Arcang.) Sacc., was controlled by applying various polymer coatings or an aqueous solution of sodium or potassium bicarbonate plus horticultural Sun Spray (SS) Ultra Fine Oil 1% (v/v) to plant foliage. The combined treatment (bicarbonate + oil) was more effective than either of the two materials alone. The results indicate that sodium or potassium (but not ammonium) bicarbonate solutions mixed with SS seems to be a useful biocompatible fungicide for controlling powdery mildew in euonymus plants. Some of the polymer coatings effectively reduced disease levels when applied immediately after the symptoms first appeared.
Tissue culture plantlets of Saintpaulia ionantha and Peperomia grisco-argenta were grown for 120 days in growth boxes placed in a greenhouse. The filtercovered tops of the boxes were sloped facing south, the direction of the sun, while the walls were constructed of white styrofoam board Four types of light filters covered the frames. Two blue celluloid sheets were used to alter the sunlight spectrum: one filtered out the red (B + FR), and the other removed most of the red and far-red, FR (B - FR). Two polyethylene films were formulated as light filters and diffusers: one scattered all the transmitted light and decreased the R: FR ratio (W), while the other was neutral in respect to the sunlight spectrum and did not cause light scattering (A). Vegetative growth of Saintpaulia plants was enhanced under the light-diffusing filters, resulting in higher fresh weight and larger leaves. Saintpaulia plants flowered first under the W filter, then the A filter, and last under the B + FR filter; no flowering occurred in the absence of FR light (B - RR). There was no significant difference in the development of Peperomia plants grown under the different filters. The results are discussed in relation to plant adaptation to various environments.
Potted Cordyline terminalis L. `Prins Albert', a foliage plant, was treated with foliar sprays or growth medium drenches of paclobutrazol for plant growth control. Paclobutrazol effectively reduced shoot length measured 4 months following application, the drench being more effective than the spray. Application of paclobutrazol at 200 ppm by either method gave a desirable compact and marketable product. Drench applications at 1000 ppm promoted side-shoot formation. Leaf morphology was altered from an elongated to a more oval form as the paclobutrazol concentration increased, but leaf count was not affected by paclobutrazol, except for the highest drench concentration, which reduced leaf count by 10%. Chemical name used: β– [(4-chlorophenyl)methyl] –α– (1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Antitranspirants (‘Vapor Gard’ and ‘Wilt Pruf’) effectively controlled powdery mildew on Hydrangea macrophylla Thunb. and Lagerstroemia indica Nana. A 2% antitranspirant emulsion was sufficient to suppress the pathogen’s development without causing visible phytotoxic effect or plant growth inhibition. The antitranspirants were as effective, and in some cases more effective (‘Vapor Gard’), than the systmic triazole fungicide ‘Tilt’ in controlling the disease. Hydrangea and dwarf Lagerstroemia (crapemyrtle) are grown commercially as flowering pot plants. Disease-free plants are required. Powdery mildew (Erisiphe polygoni DC) often causes severe damage on greenhouse-grown hydrangea. This fungus usually appears 1st on the lower leaf surface, where it produces a white, loose, cottony mycelium. Yellowish or purple-white blotches with mycelium also can be observed on the upper surface of the leaf. When the disease develops under favorable environmental conditions, the symptoms cover not only the entire leaf surface but also the bud clusters and flowers (11). Various fungicides control powdery mildew under greenhouse conditions.
Stock plants of Pelargonium zonale `Empress' were grown for 130 days on coarse tuff medium in a greenhouse. Four N concentrations (50, 100,200, and 400 mg N/liter) and three NO3-: NH4+: ratios (70:30, 60:40, and 40:60) were applied. The development of mother plants, production of cuttings, and the recovery of applied N were measured. Number of cuttings was not affected by any treatments except for the low N concentration. The proportion of absorbed N was higher than that of water in the plants treated with 50 or 100 mg N/liter, while those fertilized with 200 or 400 mg N/liter absorbed more water relative to N uptake. Nitrogen recovery efficiency decreased from 70% to 10% for the 50- to 400-mg N/liter treatments, respectively. Percentage of applied N lost by leaching (30% to 70%), and N that could not be accounted for (0.5% to 20%), increased with increasing N concentration and NH4+ percentage in the solution. The minimum concentration to be used in fertilization of Pelargonium mother plants is 100 mg N/liter. Optimal N supplied ranged between 100 and 200 mg N/liter.
Ocean spray carried by wind was determined from soil and leaf analysis, determination of salt content in the atmosphere, and meteorological data to be the main cause for the destruction of vegetation along the Mediterranean coast of Israel. An overhead sprinkling system, which was activated when the wind speed reached a critical level, prevented plant damage.
The cultivation of a wide range of ornamental plants in a closed hydrosolaric greenhouse was studied. The hydrosolaric greenhouse was composed of a solar energy harvesting system and a hydroponic system. Energy collected by the greenhouse air from the sun during the day was conserved in the growth solution, which released it during the night. This system was able to maintain the air temperature 6 C above the outdoor temperature during the night. Relative humidity ranged between 85 and 100%, thus providing a favorable environment for tropical foliage plants. Philodendron bipinnatifidum Schott, Gardenia jasminoides Ellis, Ficus benjamina L., F. lyrata Warb., Anthurium andreanum Lind and Brassaia actinophylla Endl. produced under this system were of excellent quality.