H 2 O was studied using an infinite dose diffusion system ( Bukovac and Petracek, 1993 ). In this system, 3 H 2 O diffusion was followed from a donor solution containing FeCl 3 (pH 2.6) through an interfacing ES into a water receiver of pH values
Holger Weichert, Stefanie Peschel, Moritz Knoche, and Dieter Neumann
G. J. Keever and J. S. Jacobson
Greenhouse-grown plants of Zinnia elegans Jacq. were exposed to simulated sulfuric acid rain 30 minutes per day twice a week for 6 weeks at pH 2.8, 4.0, and 5.6. Injury occurred primarily to older, mature leaves and cotyledons at pH 2.8 and 4.0 and to ray flowers at pH 2.8. Plants supplied with higher levels of Hoagland’s nutrient solution grew more rapidly, contained greater quantitities of foliar K, P, and Ca, and exhibited more foliar injury after exposure to acidic simulated rain (SR). Dry weight of plants given full-strength nutrient solution (highest level) was depressed at pH 2.8 and increased at pH 4.0 relative to pH 5.6. Loss of 86Rb by leaching from foliage was significantly increased at pH 2.8, but no differences in total foliar content of K, P, and Ca were detected.
Philip L. Forsline, Robert J. Dee, and Richard E. Melious
In a greenhouse experiment, Malus hupehensis (Pamp.) Rehd. seedlings were treated weekly with simulated acid rain solutions ranging from pH 2.25 to pH 7.0. Necrotic lesions developed on leaves at pH 2.25 and pH 2.50 immediately after the first application at the 8-node stage. Following the 9th weekly application on seedlings with 23 to 26 nodes, lesions developed at pH levels up to 3.25. At final destructive harvest, 20% of the leaf area at pH 2.25 and 8% of the leaf area at pH 2.50 was injured. Significant growth reduction occurred at these 2 pH levels. Regression analysis indicated extensive growth inhibition at <pH 3.0, no growth inhibition around pH 3.5, some inhibition between pH 4.5 and pH 5.6, and normal growth at pH 7.0 in comparison to the unsprayed control. Growth was negatively correlated with lesion formation at 3 destructive harvest dates. Relative growth rates were reduced only at pH 2.25 and pH 2.50 and reduction in the unit leaf rate was also observed. Lesion development continued to increase on the basal leaves through the 6th weekly application but leveled off during the final applications. Negative correlations of photosynthesis rate to lesion percentage and dry weight to lesion percentage were observed.
Philip L. Forsline, Robert C. Musselman, Walter J. Kender, and R. J. Dee
Mature ‘McIntosh’, ‘Empire’, and ‘Golden Delicious’ apple trees (Malus domestica Borkh.) were sprayed with simulated acid rain solutions in the pH range of 2.5 to 5.5 at full bloom in 1980 and in 1981. In 1981, weekly sprays were applied at pH 2.75 and pH 3.25. Necrotic lesions developed on apple petals at pH 2.5 with slight injury appearing at pH 3.0 and pH 3.5. Apple foliage had no acid rain lesions at any of the pH levels tested. Pollen germination was reduced at pH 2.5 in ‘Empire’. Slight fruit set reduction at pH 2.5 was observed in ‘McIntosh’. The incidence of russetting on ‘Golden Delicious’ fruits was ameliorated by the presence of rain-exclusion chambers but was not affected by acid rain. With season-long sprays at pH 2.75, there was a slight delay in maturity and lower weight of ‘McIntosh’ apples. Even at the lowest pH levels no detrimental effects of simulated acid rain were found on apple tree productivity and fruit quality when measured as fruit set, seed number per fruit, and fruit size and appearance.
Molly Felts, Renee T. Threlfall, John R. Clark, and Margaret L. Worthington
cartridge (30 × 4.5 mm) was used for a guard column. The columns were maintained at 65 °C by a temperature control unit. The mobile phase consisted of a pH 2.28 solution of sulfuric acid and water with a resistivity of 18 m , obtained from a Millipore Milli
W. Garrett Owen
the optimal substrate pH to produce high-quality flowering calceolarias. Therefore, the objectives of this research were to determine 1) the optimal incorporation concentration(s) of dolomitic and/or hydrated lime to adjust substrate pH; 2) the
Panayiotis A. Nektarios, Serafim Kastritsis, Nikolaos Ntoulas, and Panayiota Tsiotsiopoulou
acidic pH (2.8 to 4.5) and may be used to lower the pH of alkaline soil. It is readily available in most countries. UFRF could be considered a potential substitute for peat because it possesses similar physical characteristics and pH values. UFRF has been
David W. Reed and H. B. Tukey Jr.
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.
David W. Reed and H. B. Tukey Jr.
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.
Warren E. Shafer, Ronald D. Morse, and Martin J. Bukovac
The effects of pH and temperature were determined on NAA sorption by enzymatically isolated tomato (Lycopersicon esculentum Mill. cv. Sprinter) fruit cuticles. Both cuticular membranes (CM) and dewaxed CM (DCM) sorbed more NAA at pH 2.2 than at pH 6.2. At each pH, increasing temperature (15° to 35°C) decreased NAA sorption by both CM and DCM. The same qualitative temperature (5° to 25°) response was observed with 2,4-D for CM at low (0.8) pH. Chemical names used: 2-(1-naphthyl)acetic acid (NAA); (2,4-dichlorophenoxy)acetic acid (2,4-D).