Bract edge burn (BEB) starts as a necrosis on veins near the margins of mature bracts. Typically, BEB first appears at anthesis and symptoms progress over time. In 1993, the incidence of BEB on plants sprayed with sodium silicate (Na2SiO3)—490 ppm Si at weekly intervals during bract development—was compared to unsprayed controls using the cultivar Supjibi. BEB appeared soon after anthesis on unsprayed plants, and, by 309 days post-anthesis, 11.5% of the bracts on unsprayed plants had BEB, but only 0.4% of the bracts on Na2SiO3-treated plants had symptoms. Calcium levels in bract margins were similar (0.194% in both treatments. In 1994, the following spray treatments were applied weekly from 31 Oct. to 5 Dec. (initial anthesis) to the cultivars Supjibi and V-17 Angelika White: CaCl2 (400 ppm Ca), Na2SiO3 (50, 100, 150, or 200 ppm Si), DI H2O (sprayed control), or unsprayed control. Both cultivars developed similar BEB symptoms and responded similarly to all treatments. One week post-anthesis, 5.7% of the bracts on unsprayed plants (averaged for both cultivars) developed BEB and 2.5% of the bracts on sprayed controls developed BEB, but only 0.19% of the bracts on CaCl2- or Na2SiO3-treated plants developed BEB symptoms. By 5 weeks post-anthesis, the incidence of BEB was similar for plants sprayed with CaCl2 and Na2SiO3 at 100, 150, or 200 ppm (1.1%, 6%, 6.7%, and 5.7%, respectively); but higher on sprayed controls (22%), and still higher on unsprayed plants (28.5%).
Richard McAvoy and Bernard Bible
Sophia Kamenidou, Todd J. Cavins and Stephen Marek
Si), five weekly sodium silicate (NaSiO 3 ) foliar applications (50, 100, and 150 mg·L −1 Si), and five weekly KSiO 3 substrate drenches (50, 100, and 200 mg·L −1 Si). The rice husk ash was a natural byproduct with high Si content (Riceland
Jeffrey H. Gillman and David C. Zlesak
Richard J. McAvoy and Bernard B. Bible
Silica sprays (Na2SiO3 or SiO2·nH2O) markedly reduced the incidence and severity of bract necrosis (BN) of Euphorbia pulcherrima Willd. cv. Supjibi Red compared to plants not sprayed with silica. BN has been associated with low Ca concentrations or high K: Ca ratios in tissues of bract margins. Silica had no effect on Ca or K concentrations in bract margin tissues, and BN was not associated with the macro- or micronutrient composition of bract margin tissues. Sixteen days after initial anthesis, nontreated and deionized-water-sprayed poinsettias developed a higher incidence of BN than did plants sprayed with Na2SiO3 or CaCl2. However, sprays of 3.56, 5.34, and 7.12 mm Na2SiO3 were as effective as 9.98 mm CaCl2 sprays in protecting against BN of `Supjibi Red' and `Angelika White' bracts for up to 30 days after initial anthesis. `Supjibi Red' developed a higher incidence of bract necrosis than did `Angelika White', but both cultivars showed a similar response to the treatments and similar symptoms of necrosis. In both cultivars, initial symptoms appeared as small necrotic lesions on bracts at the looped ends of lateral veins that displayed a closed-vein pattern after the plants reached initial anthesis.
Shiow Y. Wang and Gene J. Galletta
The effect of silicon (Si) foliar applications on metabolic changes and powdery mildew infection in strawberry plants were determined. Silicon was used in the forms of potassium (K) and sodium (Na) salts. Foliar sprays containing 0, 250, 500, 750, and 1000 ppm of Si were applied. Strawberry plants showed no difference in response to the K or Na salts of Si during the seven weeks of experimental period. Plants treated with potassium and sodium silicate showed reduced severity of powdery mildew, increased chlorophyll content, and increased plant growth. Potassium and sodium silicate treatments also induced metabolic changes such as an increase in citric acid and malic acid levels, and a decrease in fructose, glucose, sucrose, and myoinositol content. The treated tissues also had higher ratios of (18:2 + 18:3)/18:1 in glycolipids and phospholipids and elevated amounts of membrane lipids in leaves and petioles. These results suggest that Si has beneficial effects on strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.
Susan Switras and Jeffrey Gillman
Syringa vulgaris L. `Montaigne' (French hybrid lilac) and Chionanthus virginicus L. (white fringetree) stock plants were sprayed with two film-forming antitranspirants, Clear Spray and sodium silicate, and one stomate-regulating antitranspirant, atrazine. After 30 days of growth, cuttings were taken from both species. Shoot calipers of antitranspirant-treated lilacs increased at a slower rate than the control lilacs. There were no long-term shoot length changes in lilac due to antitranspirant treatments. Shoots of Clear Spray-treated fringetrees increased in length significantly less than other treatments. Rooting was evaluated once a week from week 3 until 6 weeks after cuttings were taken for lilac and every 2 weeks from week 6 to 12 weeks after sticking for fringetree. All treatments resulted in 80% to 85% rooting in lilac after 6 weeks, but Clear Spray-treated plants rooted more quickly. Fringetree cuttings treated with Clear Spray had a significantly lower rooting percentage (15%) than the other treatments (35% to 50%).
Sophia Kamenidou and Todd Cavins
Silicon (Si) is a nonessential element that has proven to be a beneficial supplement to agricultural crops. In floriculture greenhouse production, soilless substrates have limited Si content and supplements may improve plant quality. The objective of this study was to determine Si sources, rates, and application methods to improve plant quality. Zinnia elegans `Oklahoma Formula Mix', Helianthus annuus `Ring of Fire', and Gerbera `Acapella' were provided potassium silicate (KSiO3) as a media incorporated flakes or weekly drench, sodium silicate (NaSiO3) as weekly foliar spray or ashed rice hulls. Zinnia and Helianthus Si levels were highest in leaf (0.5% to 1.7%), followed by flower (0.3-0.5%) and stem (0.2-0.4%) tissues. Gerbera accumulated lower amounts of Si compared to Zinnia and Helianthus with similar leaf and flower content values ranging from 0.4% to 0.6% with stem values 0.4% Si. Depending on source and rate, several horticultural traits were improved. Zinnia benefits included stem thickness, increase in flower diameter and stem erectness. Helianthus Si supplementation resulted in increased stem thickeness and flower diameter. However, phytotoxicity problems occurred with Si rates above 200 mg·L–1 (SiO2 applied as weekly potassium silicate drench). Gerbera stems thickened with KSiO3 and NaSiO3 applications, but NaSiO3 foliar sprays increased stem length, flower diameter and resulted in earlier flowering.
Andrew G. Reynolds, Margaret Cliff, Douglas A. Wardle and Marjorie King
Eighty-five cultivars, selections and clones of winegrapes (Vitis) from European breeding and selection programs were evaluated between 1993–95 in a randomized completeblock experiment. These included selections from Alzey, Freiburg, Geilweilerhof, Geisenheim, Weinsberg, and Würzburg (Germany); Hungary; and the former USSR. Vines were grown under an organic management regime that included sodium silicate sprays for powdery mildew (Uncinula necator) control and oil + detergent for insect control but with little to no nitrogen or other nutritional inputs. The Weinsberg cultivars Heroldrebe and Helfensteiner showed promise viticulturally and sensorially as alternatives to `Pinot noir'. Cultivars from Geisenheim (`Gm 7117-10' and `Gm 7117-26') and Würzburg (`Cantaro' and `Fontanara') appeared promising as `Riesling' alternatives; many displayed similar sensory characteristics to `Riesling', along with reasonable viticultural performance. Cultivars selected at Alzey (`Faberrebe'), Freiburg (`Nobling'), and Weinsberg (`Holder') displayed sensory characteristics superior to the standard cultivar Müller-Thurgau, with very intense muscat, pear, fig, and spicy aromas and flavors. Several muscat-flavored Hungarian white wine cultivars appeared to be superior viticulturally and sensorially to the standard `Csabagyongye'; these included `Kozma Palne Muscotaly', `Zefir', and `Zengo'. Miscellaneous red wine cultivars that showed promise included Geilweilerhof cultivar Regent, and Hungarian selections Kozma 55 and Kozma 525. Vine yields decreased substantially in the 3-year evaluation period, primarily due to lack of nitrogen. Many of these cultivars appeared to be highly adaptable to viticultural regions where cold winters and low heat units during fruit maturation presently restrict cultivar choices.
Richard McAvoy and Bernard Bible
Bract necrosis (BN) first appears at anthesis, and symptoms become more numerous and severe with time. Previously, we reported that 3.6 mm sodium silicate (Na2SiO3) sprays, applied during bract development, were as effective as 10 mm CaCl2 sprays at suppressing BN on `Supjibi' and `Angelika White', but only for several weeks after initial anthesis. While applying Na2SiO3 during bract development dramatically suppressed BN (7.2% of bracts with BN 46 days after anthesis vs. 33.4% for untreated plants), applying Na2SiO3 after anthesis is ineffective (35.7% BN). In 1995, suppression of BN was evaluated on `Supjibi' plants sprayed with similar concentrations (2 or 4 mm) of Na2SiO3 and CaCl2; treatments were compared to unsprayed poinsettias, or plants sprayed with either deionized (DI) water, 4 mm SrCl2, 4 mm NaCl, 4 mm MgCl2, or a solution of Na2SiO3 plus CaCl2 (1 or 2 mm each). At harvest (38 days after initial anthesis), 40.6% of the bracts on unsprayed plants and 35.8% of the bracts on DI water sprayed plants had BN. In contrasts, only 5.3% of the bracts on the 4 mm CaCl2 treated plants and 5.9% of the bracts on 4 mm Na2SiO3 treated plants had BN. Plants sprayed with 4 mm SrCl2 or the combination of 2 mm Na2SiO3 plus 2 mm CaCl2 developed BN on 7.8% and 9.2% of bracts, respectively. NaCl and MgCl2 sprays (4 mm) were not as effective (29.6 and 26.4% BN) as Ca, Si, or Sr sprays at suppressing BN over the duration of this study.
Qi Chai, Xinqing Shao and Jianquan Zhang
period ( Liu et al., 2009 ). Treaments. The experiment consisted of six treatments including a control (no salinity and no Si amendment) and Si amendment at 0, 0.24, 0.48, 0.72, and 0.96 g Si/kg soil levels under salinity stress. Sodium silicate used as a