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- Author or Editor: David W. Reed x
The effects of cations vs. anions in salinity studies cannot be separated by traditional means. Analysis of mixture experiments allows ionic ef-fects to be analyzed individually by varying proportions of ions without changing their total concentrations. A series of mixture experiments were performed in the greenhouse to determine the effects of the anions bicarbonate, chloride, and sulfate, given a constant and equal concentration of the cation sodium, on vinca `Pacifica Red' grown with different irrigation systems and leaching fractions. In subirrigation, increasing total ion concentrations from 30 to 60 meq/L total ion concentrations (TIC) caused a general decrease in shoot fresh and dry weights, with bicarbonate contributing to the greatest degree of reduction, and sulfate the least. Root dry weight was similarly decreased with increasing TIC, but the differences between individual ion effects were more subtle. SPAD data, an indication of chlorophyll concentration, showed a sharp decrease with increase in bicarbonate, but not with sulfate or chloride. Medium pH increased as TIC increased, being influenced primarily by bicarbonate. Conversely, growing medium EC was influenced most by sulfate and chloride, and least by bicarbonate with increasing TIC. At 30 meq/L TIC, top-watered treatments with a leaching fraction (LF) of 5% generally had reduced shoot and root dry weight without regard to ion species, while a leaching fraction of 35% produced results more similar to those of subirrigation. While medium EC and pH varied with layer and irrigation method, bicarbonate generally affected EC least and pH most.
Greenhouse cultural methods must change rapidly to minimize runoff and to keep pace with environmental regulation aimed at protecting water resources. Two experiments were designed to investigate the effect of N fertilization rate on New Guinea impatiens (Impatiens ×hawkeri) and peace lily (Spathiphyllum Schott) in an ebb-and-flow subirrigation system. Maximum growth response for impatiens was centered around 8-mM N levels as measured by root and shoot fresh and dry weight, height, leaf number, leaf area, and chlorophyll concentration. For peace lily, growth peaked around 10 mM N. Growing medium was divided into three equal layers: top, middle, and bottom. Root distribution favored the middle and bottom layers, and the relative distribution of roots was consistent as N level increased. Soluble salts remained low in middle and bottom layers at N concentrations below 10 mM, but increased significantly for all soil layers at levels above 10 mM. The top layer contained two to five times higher soluble salt levels than in the middle or bottom layers at all N levels. Increased nitrate concentration mimicked increases in soluble salts, while pH decreased as N concentration increased for both impatiens and peace lily.
Introductory horticulture courses are taught in almost every 4 year and 2 year horticulture program across the country, however, purpose, content and approach can vary widely among schools. Survey results will show how different schools use their introductory course (recruiting, foundation, service), class composition, topics most commonly included, textbooks used, standard teaching techniques and new or innovative techniques that have been especially effective.
Greenhouse cultural methods must minimize runoff to keep pace with environmental regulation aimed at protecting water resources. Two experiments were designed to investigate the effect of N fertilization rate on New Guinea impatiens (Impatiens ×hawkeri) and peace lily (Spathiphyllum Schott) in an ebb-and-flow subirrigation system. Maximum growth response for impatiens was centered around 8 mm N levels as measured by root and shoot fresh and dry weight, height, leaf number, leaf area, and chlorophyll concentration. For peace lily, growth peaked at about 10 mm N. Growing medium was divided into three equal layers: top, middle, and bottom. Root distribution favored the middle and bottom layers, and the relative distribution of roots was consistent as N level increased. EC remained low in middle and bottom layers at N concentrations below 10 mm, but increased significantly for all layers at levels above 10 mm. The EC for the top layer was 2 to 5 times higher than in the middle or bottom layers at all N levels. Increased nitrate concentration paralleled increased EC, while pH decreased as N concentration increased for impatiens and peace lily.
The ultrastructural localization of polysaccarides in Malus domestica Borkh. leaf cuticles was investigated by electron microscopy staining. The cuticle/cell wall interface was not stained by ruthenium red or hydroxylamine-ferric chloride, indicating the lack of a distinct pectin layer. The inner region of the cuticle was intensely and uniformly stained by phosphotungstic acid (PTA) and was lightly stained by silver proteinate, indicating the presence of polysaccharides, which in part may be pectin as indicated by staining with ruthenium red. Fibrils in the inner region of the cuticle were not stained by ruthenium red, hydroxylamine-ferric chloride or silver proteinate, but appeared lightly stained by PTA; this suggests by deduction that the fibrils may consist of cutinized cellulose. The outer region of the cuticle was not stained by any of the staining procedures, indicating the lack of polysaccharides.
At either 440 or 145 μEm−2s−1, greater amounts of cuticle, cutin matrix, and wax were formed at 15° than 25°C on leaves of Brussels sprouts (Brassica oleraceae. L., Gemmifera group), but the reverse occurred on leaves of carnation (Dianthus caryophyllus L.). At either 15 or 25°, greater amounts of cuticle, cutin matrix, and wax were formed at 440 than 145 μEm−2s−1 on both species. For Brussels sprouts, at 25°/440 μEm−2s−1 and 25°/145 μEm−2s−1, large parallel wax dentrites covered the leaf surface. At 15°/440 μEm−2s−1, dentrites were smaller and morphologically less elaborate. At 15°/145 μEm−2s−1, epicuticular wax occurred as scattered rods perpendicular to the leaf surface. Carnation epicuticular waxes consistently occurred as rods, but as temperature and/or light intensity decreased, rod length decreased and density increased. There were no changes in internal cuticle ultrastructure of either species in different environments, but cuticle thickness increased as temperature and light intensity decreased. Epicuticular waxes visualized in surface view by scanning electron microscopy (SEM) were extracted by procedures for transmission electron microscopy (TEM) observation.
Solution pH differentially affected the foliar absorption of phosphorus compounds by Chrysanthemum morifolium Ramat cv. Giant #4 Indianapolis White. All phosphates were absorbed readily at pH 2, which was accompanied by necrosis of the treated area of the leaf. Maximum absorption occurred with Na phosphate at pH 3-6, K phosphate at pH 7-10, and NH4 phosphate at all pH values (3-10), whereas Ca phosphate was not readily absorbed. The results could be explained by pH dictating the phosphate form present in solution; solubility, moisture retention, and crystallization on the leaf surface of the predominant phosphate salt were the factors determining the degree of absorption.
Foliar absorption of RbCl, RbNO3 and Rb2SO4 by Chrysanthemum morifolium Ramat. cv. Giant No. 4 Indianapolis White was greatest at pH 2, at which there was considerable leaf damage, but changed little at pH 3-10. Absorption of RbCl was greater than RbNO3 or Rb2SO4 regardless of pH. Absorption of Rb and phosphate as Rb phosphate was minimal at pH 3-6, but was greatly increased at pH 7-10. These results may be explained by the degree of drying and crystallization of the applied compounds on the leaf surface.
Ficus benjamina L. and F. stricta Miguel. were exposed to various concentrations of ethylene gas and ethephon to determine their sensitivity to defoliation. F. stricta was more sensitive to ethephon, whereas F. benjamina was more sensitive to ethylene gas. Plants growing in medium exposed to ethylene gas depleted ethylene from the ambient atmosphere. Double-autoclaving the peat : perlite growing medium prevented ethylene depletion, indicating soil microbes as the source of depletion. Bacterial isolates from the medium depleted ethylene in vitro; fungal isolates did not deplete ethylene. The eight species of bacteria isolated into pure culture depleted 9% to 46% of the ethylene from the flask atmosphere over 5 days, with two Enterobacter spp. and one Pseudomonas sp. being the most effective depleters. Chemical name used: (2-chloroethyl)phosphonic acid (ethephon).
The objective of this study was to quantify the optimum rates of water-soluble phosphorus (P) under constant nitrogen and potassium on the growth of new guinea impatiens (Impatiens hawkeri Bull.) `Paradise Violet' and vinca Catharanthus roseus `Pacifica Red' in soilless media in a recirculating subirrigation system. The experiment was designed so that only phosphate varied between treatments while all other nutrients remained constant. The ammoniacal N to nitrate N ratio was varied to counter balance increases in phosphate. Sodium was used as a counter ion to phosphate at higher concentrations of phosphate; sodium proved to be toxic at concentrations above 6 mm. In the new guinea impatiens experiment, there was a small increase in K due to the use of dibasic K phosphate to buffer pH. All growth parameters measured (height, leaf number, flower number, and shoot fresh and dry weight) showed significant differences with increasing P rate. Depending on the growth parameter measured, quadratic–linear models revealed an optimum P rate of 0.1 to 0.96 mm for new guinea impatiens `Paradise Violet' and 0.45 to 1.25 mm P for vinca `Pacifica Red'. For dry shoot weight, a common measure of optimum plant growth, the optimum P rate was 0.75 mm P for new guinea impatiens `Paradise Violet' and 0.67 mm P for vinca `Pacifica Red'. For flower number, a common measure of floral quality, the optimal P rate was 0.96 mm P for new guinea impatiens `Paradise Violet' and 1.25 mm P for vinca `Pacifica Red'. Electrical conductivity (EC) of the growing media increased significantly with increasing rate of P. At all rates, EC was significantly greater in the top layer than in the bottom and middle layers. The pH of the growing medium did not vary in relation to P concentration.