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Hector R. Valenzuela, Osamu Kawabata and Harry Yamamoto

Methanol sprays reportedly increased yields of several crops in Arizona by 50 to 100 percent (Nonomura and Benson PNAS 89:9794(1992). Reports from other parts of the country have shown conflicting results with regards to the effect of methanol sprays on yields of horticultural crops. Several greenhouse and growth chamber (controlled temperature. day length, and photosynthetic photon flux) experiments were conducted to evaluate the effect of methanol sprays on the growth and productivity of several vegetable crops in Hawaii. Treatment spray solutions consisted of 20-25% methanol, 0.5% low biuret urea. 0.001% chelated iron, and 0.02% surfactant. Control sprays only contained urea, chelated iron, and surfactant. Each experiment consisted of at least 5 weekly methanol sprays. Flowering cabbage, Brassica campestris var. parachinensis, had greater biomass production when sprayed with methanol in the late summer months. Similar results were obtained with choi sum in a 2 by 2 factorial experiment with methanol and water stress treatments. However, choi sum did not respond to methanol treatments in follow-up greenhouse trials. perhaps attributable to the shorter and Overcast days experienced in the fall and winter. Okra, chili pepper, and eggplant showed no response to methanol sprays. Okra showed a trend toward increase yields in response to methanol sprays, but differences were not significant. Follow-up studies in the greenhouse and in the field, which include evaluation of photosynthetic efficiency through chlorophyll fluorescence determinations will be presented.

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Lane Greer and John M. Dole

Six defoliants were applied in fall and tested for their efficacy in preharvest defoliation of fieldgrown curly willow (Salix matsudana `Tortuosa'), american bittersweet (Celastrus scandens), and american beautyberry (Callicarpa americana). Defoliants included acetic acid, chelated copper, crop oil concentrate surfactant (COC), ethephon, dimethipin plus COC, pelargonic acid, and a tap water control. For chelated copper, a concentration of 800 mg·L–1 (ppm) was most effective at promoting defoliation, providing 100% defoliation of american bittersweet and 76% defoliation of american beautyberry. For curly willow and american beautyberry, all concentrations of dimethipin produced good or excellent defoliation. Increasing concentrations of ethephon from 200 to 2500 mg·L–1 increased defoliation from 0% to 67%. Pelargonic acid was not effective at promoting defoliation of woody plants at the concentrations used. In an experiment conducted during spring using containerized curly willow, irrigation was stopped for 0, 3, or 6 days before defoliants were applied, but none of the irrigation treatments promoted defoliation. In a postharvest study using cut curly willow, stems were held in distilled water at 5, 20, or 35 °C (41.0, 68.0, or 95.0 °F) for 1, 3, 5, or 7 days. Holding cut stems of curly willow at 20 °C promoted 68% defoliation, compared to 53% or 28% for 5 or 35 °C, respectively.

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Timothy K. Broschat and Kimberly K. Moore

Zonal geraniums (Pelargonium ×hortorum) from seed and african marigolds (Tagetes erecta), which are known to be highly susceptible to Fe toxicity problems, were grown with I, 2, 4, or 6 mm Fe from ferrous sulfate, ferric citrate, FeEDTA, FeDTPA, FeEDDHA, ferric glucoheptonate, or ferrous ammonium sulfate in the subirrigation solution. FeEDTA and FeDTPA were highly toxic to both species, even at the 1 mm rate. Ferrous sulfate and ferrous ammonium sulfate caused no visible toxicity symptoms on marigolds, but did reduce dry weights with increasing Fe concentrations. Both materials were slightly to moderately toxic on zonal geraniums. FeEDDHA was only mildly toxic at the 1 mm concentration on both species, but was moderately toxic at the 2 and 4 mm concentrations. Substrate pH was generally negatively correlated with geranium dry weight and visible phytotoxicity ratings, with the least toxic materials, ferrous sulfate and ferrous ammonium sulfate, resulting in the lowest substrate pHs and the chelates FeEDTA, FeDTPA, and FeEDDHA the highest pH. The ionic Fe sources, ferrous sulfate and ferrous ammonium sulfate, suppressed P uptake in both species, whereas the Fe chelates did not. Fe EDDHA should be considered as an effective and less toxic alternative for the widely used FeEDTA and FeDTPA in the production of these crops.

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Lane Greer and John M. Dole

Six defoliants were applied in fall and tested for their efficacy in preharvest defoliation of field grown curly willow (Salix matsudana `Tortuosa'), american bittersweet (Celastrus scandens), and american beautyberry (Callicarpa americana). Defoliants included acetic acid, chelated copper, crop oil concentrate (COC), ethephon, dimethipin plus COC, pelargonic acid, and a tap water control. For chelated copper, a concentration of 800 mg·L–1 was most effective at promoting defoliation, providing 100% defoliation of american bittersweet and 76% defoliation of american beautyberry. For curly willow and american beautyberry, all concentrations of dimethipin produced good or excellent defoliation. Increasing concentrations of ethephon from 200 to 2500 mg·L–1 increased defoliation from 0% to 67%. Pelargonic acid was not effective at promoting defoliation of woody plants at the concentrations used. In an experiment conducted during spring using containerized curly willow, irrigation was stopped for 0, 3, or 6 days before defoliants were applied, but none of the irrigation treatments promoted defoliation. In a postharvest study using cut curly willow, stems were held in distilled water at 5, 20, or 35 °C for 1, 3, 5, or 7 days. Holding cut stems of curly willow at 20 °C promoted 68% defoliation, compared to 53% or 28% for 5 or 35 °C, respectively.

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Faissal F. Ahmed, Ahmed M. Akl and Farag M. El-Morsy

During 1995 and 1996, yield and quality of `Banaty' grapes in response to spraying chelated iron and zinc singly or in combination each at 0.025%, 0.05%, 0.1%, 0.2%, or 0.3% was investigated. Each concentration was applied once, twice, three, four, or five times. Results showed that there was a gradual increase in berry set, cluster number, yield, cluster weight, berry weight, total soluble solid sugars, and total anthocyanins with rising concentrations and number of sprays of each fertilizer. Total acidity tended to reduce with such treatment. Combined spray of both fertilizers, particularly at 0.1% four times, gave satisfactory improvement in both quantity and quality of grapes. Spraying at concentrations higher than 0.1% or spraying more than four times failed to show any measurable effect on all of the studied traits. The best results with regard to yield and quality of `Banaty' grapes were obtained on vines that received four sprays of iron and zinc each at 0.1% in chelated form.

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Jake F. Browder, Alexander X. Niemiera, J. Roger Harris and Robert D. Wright

Substrates of container-grown plants are commonly preplant amended with sulfated micronutrients to supply micronutrients. However, the cause for the increased growth may be due to micronutrient addition or other factors such as S addition or substrate acidification. Container-grown pin oak (Quercus palustris Müench) and japanese maple (Acer palmatum Thunb.) seedlings were grown in a 100% pine bark substrate and amended (or not) with one of the following treatments: control (no amendment), Micromax, K2SO4, H2SO4, HCl, chelated micronutrients, elemental S, or CaSO4. After 11 weeks, dry weights of plants in all treatments supplying S were higher than plants receiving no S. Dry weights of plants in all experiments receiving the chelate treatment were not higher than dry weights for control plants. These data indicate that S, not micronutrient application, is a primary cause of increased growth from the addition of sulfated micronutrients. However, it was demonstrated that there are conditions such as higher substrate solution pH (4.1 vs. 5.4), where Micromax may prove advantageous over sulfur alone since it would supply micronutrients as well as S.

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Frank J. Peryea

Postbloom zinc (Zn) sprays are replacing dormant and postharvest sprays as the primary means for applying Zn in commercial apple (Malus ×domestica) orchards. We conducted a multiyear field study comparing the phytoavailability of Zn in 11 commercially available Zn spray products, plus reagent-grade Zn nitrate and a water-sprayed control, applied postbloom at identical Zn concentrations to `Golden Delicious' apple trees. Two sprays were applied per season (mid-May and mid-June), at per-spray rates of either 0.5 lb/acre in 2000 or 1.0 lb/acre in 2001 and 2002. No sprays were applied in 2003 in order to evaluate carry-over effects. The Zn sprays had no effect on fruit number, bitter pit or russeting, or on leaf green color. Zinc concentrations of detergent plus acid-washed leaves (a procedure used to remove surface residues of the Zn sprays) sampled in August and of unwashed winter buds sampled the following January were used as indices of tree Zn status. Leaf Zn concentration generally increased in the order: Zn phosphate < Zn oxide = Zn oxysulfate < chelated/organically complexed Zn ≤ Zn nitrate. There was little consistent difference among chelated and organically complexed Zn products. Leaf Zn concentration varied considerably between seasons, and was not related to Zn application rate. All of the Zn sprays increased leaf Zn concentrations to desirable levels. Because the inorganic Zn-based products typically are substantially less expensive per unit of Zn, it may be less costly and just as effective to use a higher rate of an inorganic Zn product as to use a lower rate of a more expensive chelated or organically complexed Zn product. On the other hand, use of low rates of highly phytoavailable Zn products minimizes release of the nutritionally essential but potentially ecohazardous metal into the environment. There was no detectable lasting effect of the three previous seasons of Zn sprays on leaf Zn in 2003. Similarly, there was no detectable effect in any year of the Zn spray treatments on bud Zn concentration the following winter. These results suggest that the amount of Zn supplied by the sprays at the tested rates was insufficient to promote substantial Zn accumulation within the trees, thereby validating the recommendation for annual application of Zn nutritional maintenance sprays.

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W.F. Campbell, J.L. Anderson and D.R. Walker

Calcium chloride (CaCl2) enhances turgidity and quality of postharvest sour cherry, Prunus cerasus L., fruit. Mechanisms by which plasma membrane (PM) ATPase maintains the electrochemical gradient in cell turgor were studied in isolated PM vesicles isolated from tapwater-, CaCl2- and chelated amino acid-calcium-treated Montmorency sour cherry fruit. Electron microscopy and periodic-chromicphosphotungstic acid staining indicated 85-90% closed PM vesicles. Protein activity associated with the PM was four times higher in both Ca treatments than in untreated cherries. ATPase activity was insensitive to NO3 and NaN3, but inhibited by vanadate, indicating absence or low levels of tonoplast and mitochondrial ATPases. PM vesicles exhibited a pH jump in the presence of acridine orange (A493-530nm). Cherry fruit appeared to have a PM ATPase similar to that of other plant species. Generation of a positive membrane potential across the PM was dependent upon ATP.

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J. Anthony Hopfinger, Donald W. Shaffner and Eric D. Cubberley

Both Cacl2 and Nutrical (a trihydroxyglutarate chelate) were foliarly applied at rates of 1.8 and 5.5 Cacl2/ha/season and 1.5 and 4.5 l/ha/season, respectively. Applications were made starting at shuck split and repeated at 2 week intervals until harvest. Neither calcium treatment had an effect on fruit size and size distribution. Fruit size was directly related to crop load. Calcium chloride application had the most pronounced effect on increasing the red over-color of `Cresthaven' peaches with Nutrical intermediate compared to the control. The high rate of Nutrical increased flesh calcium levels at harvest by 75-100 PPM. Instron Texture Profile Analysis indicated that any calcium treatment significantly increased the hardness of the peach. Nutrical at 4.5 l/ha/season improved hardness 2-fold compared to the controls. The improved hardness was maintained throughout the 6 week storage period.

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Yong-Soo Hwang, D.J. Huber and L.G. Albrigo

Cell wall composition and structure were examined in visually normal (N), granulated (G), and collapsed (VC) juice vesicles of `Marsh Seedless' grapefruit (Citrus paradisi) Macf.). According to gel-filtration data, VC appeared to be associated with a modification of water-soluble (WSP) and chelate-soluble (CSP) pectin molecular weight (Mr); small-Mr pectins increased, whereas large-J4. pectins decreased. The difference in M = of pectins did not appear to be mediated by polygalacturonases. Molecular weight of hemicelluloses did not differ. Granulated vesicles contained about two times more structural polysaccharides (pectins, hemicelhdose, and cellulose) than N vesicles, although hemicellulose and pectin M = modification were absent. Ion-exchange profiles of WSP, CSP, and hemicelhrlose fractions of VC and G vesicles were not different from those of N vesicles. Individual cells in vesicles with G and these vesicles themselves were much larger than those of N vesicles, whereas cells in VC were partially or completely collapsed.