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- Author or Editor: D. B. McConnell x
Abstract
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.
The effect of four shade levels (47%, 63%, 80%, and 91%) on air temperature was evaluated using 24 arch-shaped, open-ended shadestructures oriented with their longitudinal axis in north–south direction. The mini-shadehouses were 80 × 185 × 80 cm (width × length × height). Six replicates per treatment (shade level) were randomly assigned within the experimental plot. Light levels were measured using Sunceram solar cells. Copper-Constantan thermocouples were installed 60 cm from ground level and 20 cm from the north entrance. The experiment was initiated in July 1994 and terminated in Oct. 1994. Data from 20 consecutive days in August were analyzed. Eighty percent shade had the highest air temperature; however, the average difference between 47%, 63%, and 91% shade was less than 1C. Wind direction and speed affected air temperature with north or south winds correlated with highest temperatures. Analysis of the data shows averaged air temperatures differed by ≤1C for all shade levels. Consequently, these structures may be used for replicated research studies involving plant growth.
Abstract
Aglaonema ‘Silver Queen’ exposed to 4.5°, 13°, or 21°C for 10 hr each night for 1, 3, or 6 nights exhibited visual damage that increased as temperature decreased or as length of exposure increased. Growth index was negatively correlated with length of exposure in growth chambers, but exhibited no response to temperature. Leaf areas of new leaves exhibited reduced values at the lowest temperature and longest durations, but measurements of effusate conductivities, total leaf area, and number of new leaves were not affected by treatments. Microscopic examination of visually damaged leaves showed collapsed epidermal cells, while stem sections of chilled plants had a reduced number of starch grains.
Abstract
Ten-node terminal cuttings of Cordyline terminalis (L.) Kunth ‘Baby Doll’ were placed in solutions of 0, 1, 2, and 3 mg/liter F (from NH4FHF) and placed in growth chambers for 6 days at 18, 24, or 29°C. Increasing temperature and F concentration increased leaf damage. Damage ratings at 3 ppm were over 4 times greater at 29° than at 18°. Mesophyll collapse occurred only after severe epidermal collapse and chloroplast degeneration.
Abstract
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.
Abstract
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.
Abstract
Vibrations of 0.02 gravitational force (g) at 4.1 cycles per second (cps) were applied to Begonia ‘Medora’ and Schefflera arboricola (Hayata) Merrill during 6 days of simulated transit. Vibration caused leaf abscission, necrotic leaf areas, and severed stem tips. Silver thiosulfate (STS), applied as a previbration foliar spray (0, 0.28, 0.56, 1.12, mM silver), increased leaf abscission of begonias but not scheffleras during simulated transit. Ethylene emanation from stem tips of both species increased as STS concentration increased. Ethylene emanation from stem tips was not affected by vibration. During 4 weeks of simulated retail holding, STS decreased begonia leaf abscission.
Abstract
Five plant species [burford holly (Ilex cornuta Lindl. and paxt. ‘Burfordii’) golden-rain tree [Koelreuteria elegans (Seem. A.C. Sm.], ligustrum (Ligustrum japonicum Thunb.), hibiscus (Hibiscus rosa-sinensis L.), and podocarpus (Podocarpus macrophyllus Thunb.)] were arranged in a 5 × 5 × 5 factorial experiment and sprayed with 4 pesticides (dimethoate, dicofol, malathion, oxydemeton methyl) and water alone, as well as 4 chemicals [ancymidol, ethephon, gibberellic acid (GA3)] and water alone. Growth regulators increased pesticide phytotoxicity ratings, whereas the antitranspirant had no effect on phytotoxicity ratings.
Abstract
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.
Tissue culture plugs of Aglaonema `Cory', `Maria', and `Silver Queen' and Dieffenbachia `Panther', `Snowflake', and `Sport Lynn' were potted singly in 15-cm pots and grown in a shaded greenhouse under a photosynthetic irradiance (PI) of 100 mmol·m–2·s–1. Eight months after potting, 27 plants of each cultivar were placed in nine interior evaluation rooms under three different PI levels (three rooms per level): 4, 8, and 16 mmol·m–2·s–1. In addition, three plants of each cultivar were maintained in the original greenhouse for the duration of the experiment. Number of leaves, plant height and width were monitored monthly. Recently matured leaves were removed at 3-month intervals for 9 months for determination of fresh and dry weight, leaf area, and percentage leaf variegation. Variegated leaf area was assessed using digitized leaf images. Interior PI levels affected growth parameters, but the degree of response was cultivar-dependent. Smallest leaves developed on plants grown under 4 mmol·m–2·s–1 and largest leaves developed under 16 mmol·m–2·s–1. Leaf area of Dieffenbachia `Sport Lynn' showed the greatest response and Aglaonema `Maria' the least response to PI levels. Percentage leaf variegation of Dieffenbachia `Snowflake' was least affected and Dieffenbachia `Sport Lynn' was most affected by PI levels. Fresh leaf weight of unit area decreased as PI levels decreased from 16 to 4 mmol·m–2·s–1, however, the decrease in unit area was most pronounced in cultivars that maintained the highest quality ratings. Based on the results of this study, Aglaonema `Maria' and Dieffenbachia `Snowflake' had the most satisfactory interior performance within their respective genera.