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- Author or Editor: J. McConnell x
A local ground orchid, Spathoglottis plicata Blume, and coconut, Cocos nucifera L., were used in the classroom to teach seed germination. S. plicata, a common orchid on Guam, was utilized to demonstrate the aseptic culture of seeds under non-sterile conditions. The procedures were done in the classroom without a laminar air-flow cabinet. Nonsterile seeds were sown on growing media which were prepared without autoclaving, but by incorporating sodium hypochlorite into the media. Students had a high rate of success in germinating the orchid seeds without contamination by spraying sodium hypochlorite on the seeds. Different stages of coconut seed development were presented to students by simply cutting coconut in half. Unique features and botanical terms of coconut seed development can be taught throughout the year. Teaching materials on seed germination of the two tropical plants are being developed by print-on-demand methods.
Phalaenopsis species often exhibit light green spots and/or pitting of the upper leaf surface during winter and spring. Results of this study indicate spotting and pitting can be induced by exposure to temperatures of 2°, 4°, and 7°C for 8 hours or less. The spots and/or pitted areas were always found between large vascular bundles. Light green or yellow spots on the leaves were caused by hypertrophied mesophyll cells between the main vascular bundles. Anatomical observations revealed the pitting was due to collapsed mesophyll cells. Severity of response depended on physiological age of the leaf and duration of exposure to the chilling temperature.
Soil drench of (2-chloroethyl)phosphonic acid (ethephon) at 500 or 1000 mg (active ingredient)/25-cm pot, caused prostrate growth habit and fruit set on Ficus benjamina L. grown in full sun or 47% shade. Leaves of sun plants generally had a mesophyll with multiple palisade layers, while shade plants had only limited regions of multiple cells. Ethephon treatments reduced intercellular spaces in palisade and spongy mesophyll cells, particularly near leaf margins. High shoot/root ratios, reduced leaf area, and heavy leaf drop during an interior phase occurred with ethephon treatment, especially plants grown under full sun.
The effect of 0, 250, 1000, 3000, 5000, 7500, 10,000, and 15,000 ppm solution of NaCl:MgCl2 in a 10:1 ratio was determined on Chinese fan palms [Livistona chinensis (Jacq.) R Brown] grown in soil or nutrient solution. Plants grown in soil and drenched weekly with 10,000 ppm ceased growth within 2 months, while palms grown in nutrient solution exhibited a reduced growth rate with increasing salinity levels. Tissue analysis showed increased levels of Na and Mg in plant tissue with increased saline substrate levels, with highest Na and Mg tissue levels in fronds from container-grown palms.
The performance and leaching behavior of six nitrogen fertilizers on bermuda grass were studied under humid tropical conditions. The grass was established in 20 × 36 cm pots filled with 8 cm pea gravel and 28 cm of silica sand. Ammonium nitrate was applied to the turf at monthly rates between 0.25 and 6 lb/1000ft2. Performance was gauged by clipping dry weights, image analysis for greeness, and visual ratings. Leachates were checked for nitrate levels. A rate of 2 lbs/1000ft2 produced quality turf while yielding a minimum of nitrate leaching. Rates of 6 and 4 lb./1000ft2/mo. resulted in the highest readings without an increase in quality. Rates less than 2lb/1000ft2 had leachate nitrate less than 9 ppm but produced turf of unacceptable quality.
Nutralene, Nitroform, sulfur coated urea, IBDU, and AN were applied at a rate of 2 lb./1000ft/mo. The slow-release forms were applied as a 3 month dose. Performance was determined as above and nitrate leaching was monitored by weekly collections. Nutralene, SCU and Nitroform had peak nitrate levels 2 weeks after application, IBDU had peak nitrate levels after 4 weeks. Turf quality diminished at 6 weeks.
A simple and effective method for quantification of leaf variegation was developed. Using a digital camera or a scanner, the image of a variegated leaf was imported into a computer and saved to a file. Total pixels of the entire leaf area and total pixels of each color within the leaf were determined using an Adobe Photoshop graphics editor. Thus, the percentage of each color's total pixel count in relation to the total pixel count of the entire leaf was obtained. Total leaf area was measured through a leaf area meter; the exact area of this color was calculated in reference to the pixel percentage obtained from Photoshop. Using this method, variegated leaves of ‘Mary Ann’ aglaonema (Aglaonema x), ‘Ornate’ calathea (Calathea ornate), ‘Yellow Petra’ codiaeum (Codiaeum variegatum), ‘Florida Beauty’ dracaena (Dracaena surculosa), ‘Camille’ dieffenbachia (Dieffenbachia maculata), and ‘Triostar’ stromanthe (Stromanthe sanguinea) were quantified. After a brief training period, this method was used by five randomly selected individuals to quantify the variegation of the same set of leaves. The results were highly reproducible no matter who performed the quantification. This method, which the authors have chosen to call the quantification of leaf variegation (QLV) method, can be used for monitoring changes in colors and variegation patterns incited by abiotic and biotic stresses as well as quantifying differences in variegation patterns of plants developed in breeding programs.
Aphelandra squarrosa Nees. plants grown under 250 μmol s−lm−2 photosynthetically active radiation (PAR) were transferred to 265, 737, and 1070 μmol s−1m−2. Stomatal density and number of palisade layers of newly expanded leaves decreased linearly after 2 months, while number of countable chloroplasts per palisade cell increased linearly as light intensity decreased. Number of countable chloroplasts per palisade cell decreased and palisade layers increased in mature leaves transferred to higher PAR levels. Stomatal density and guard cell length in mature leaves did not change. There were nonlinear responses to PAR levels in number of marginal collenchyma cells, leaf thickness, and palisade cell length of immature leaves. Chloroplasts in mature and immature leaves were less discrete and more tightly appressed to anticlinal palisade cell walls as PAR levels increased.
Silvernerve plant (Fittonia verschaffeltii ssp. argyroneura Coem.), a chill-sensitive foliage plant, was subjected to 2°, 5°, and 8° ± 1°C for 0, 2, 4, or 8 hours. Chilling temperatues caused leaf wilt, inflorescence collapse and brown necrotic spots on the foliage. Severity of chill damage increased with temperature reduction and duration.
Light and fertilizer significantly affected light compensation point (LCP) in Ficus benjamina in a 3 × 4 factorial experiment with 0%, 30%, 55% and 80% light exclusion and of 784, 1568 and 2352 kg N+K/ha/year. Increasing shade levels decreased LCP and at each shade level increasing fertilizer rates increased LCP. Fertilizer was less effective than shade in altering LCP. The highest LCP at 0% shade and 784 kg N+K/ha/year was nearly 3 times higher than the lowest LCP at 80% shade and 784 kg N+K/ha/year. Increasing shade and fertilizer levels increased chlorophyll content, plant size and visible quality.
Plant tissue culture instructors face a dilemma when selecting laboratory exercises for large classes. Class size and equipment limitations may require that the exercises be performed without a laminar flow hood. The problem is further complicated when one attempts to choose an exercise to demonstrate adventitious shoot formation. There are few plant species from which suitable tissue explants can be obtained to demonstrate rapid adventitious shoot formation. Problems associated with surface sterilization, extended culture duration, or sporadic shoot regeneration limit the usefulness of most explants for classroom demonstrations.