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Bruce R. Roberts, Virginia M. Schnipke, and Jack H. Barger

Two-year-old seedlings of red maple (Acer rubrum L.) were fumigated with SO2 (0.0, 0.5, 2.0, and 4.0 ppm) 8 hours daily for two 3-day periods spaced 3 days apart. Response to acute SO2 stress was determined by measuring changes in ethylene biosynthesis and membrane permeability. Ethylene evolution was a useful indicator of the onset of SO2 stress in red maple, but was not a particularly good indicator of the degree of stress. Membrane permeability was not as sensitive to the initial stages of SO2 stress, and significant changes in permeability were noted only at higher concentrations of this pollutant (> 2.0 ppm).

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Lichun Mao and Tiejin Ying

Changes in respiration rate, ethylene production, and membrane permeability of fig (Ficus carica L. `Masui Dauphine', `Celeste', and `Brunswick') fruit subjected to vibration at acceleration of 4x g for 10 min were investigated. Vibration increased respiration rate significantly, which, however, declined quickly to low level soon after the treatment. Ethylene production and membrane permeability also increased significantly during vibration. However, vibration stress up to 4x g did not have significant effect on the physiological changes of the fig fruit after vibration. `Masui Dauphine' is more susceptible to vibration stress than `Celeste' and `Brunswick'.

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E. Cohen, B. Shapiro, Y. Shalom, and J.D. Klein

Water loss was found to be a nondestructive indicator before visible symptoms of chilling injury (CI) in cold-stored grapefruit (Citrus paradisi Macf.) and lemon (C. limon L. Burm. f.). The water-loss rate increased significantly after removing the fruit from cold storage and holding at 20C. Scanning electron microscopy revealed large cracks around the stomata. Changes in electrical conductivity of the flavedo tissues, total electrolyte leakage, and K+ or Ca2+ leakage were all inadequate predictors of CI, appearing only after CI was evident.

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Shohei Yamaki and Migifumi Ino

A study was conducted to determine the distribution of sugars in vacuoles, cytoplasm, and free space in apples (Malus domestica Bork) picked at the immature and mature stage of maturity. The volumes of free space and air space were 13.4% and 14.5%, respectively, in immature fruit, and 14.6% and 25.6%, respectively, in mature fruit. The inner cellular volume (vacuole + cytoplasm) was 72% and 60% for immature and mature fruit, respectively. About 90% of each sugar (glucose, fructose, sucrose, and sorbitol) was found in the vacuole. The concentration of total sugar in the inner cell or free space was 326 or 128 mm each in immature fruit and 937 or 406 mm each in mature fruit. Permeability to sugars across the plasma membrane and tonoplast also increased with fruit maturation, 7- to 30-fold for the tonoplast and 4- to 5-fold for the plasma membrane in mature compared to immature fruit. Cells in immature fruit apparently enlarge through higher turgor pressure from sequestering of sugars into vacuoles, and cease to enlarge in mature fruit as the amount of sugar unloading into the fruit is reduced due to the accumulation of sugar in the free space or cytoplasm.

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Agnes A. Flores-Nimedez, Paul H. Li, and Charles C. Shin

55108. We thank Ed and Ok Young Stadelmann for providing the facilities for membrane permeability experiments, A.H. (Bud) Markhart III for help in water relations measurements, Ed Nater for the use of a double-beam spectrophotometer, David W. Davis for

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G.A. Picchioni, S. Miyamoto, and J.B. Storey

A laboratory procedure was used to evaluate saline tolerance of pistachio rootstock species. Results were compared to those from a 2-year, outdoor lysimeter study to test reliability of the method. Excised root tips from seedlings of Pistacia atlantica Desf., P. terebinthus L. (two selections), and P. integerrima Stewart × atlantica (Pioneer Gold II, or PG II), were exposed to laboratory solutions that simulated soil solution electrical conductivity (EC) and Na: Ca ratios in the lysimeters. Following 24 hours of incubation, the efflux of ultraviolet (UV)-absorbing solutes was measured, providing an indication of cell membrane permeability. Leakage occurred with saline solutions comparable to lysimeter soil water salinity that increased leaf Na concentrations and decreased average root growth (175 mm NaCl with 12.5 mm Ca, or EC of 18.1 dS·m-l). Cell injury increased linearly with salinity (R2 = 0.81) and was highest in root tips of a P. terebinthus selection having least Na exclusion capability in the lysimeters. On average, these excised roots lost 38% more solutes than roots of a stronger Na-excluding genotype. There were no differences in leakage responses of the other species and selections. Leakage intensity was independent of various stress media, including isosmotic CaC12, mannitol, and the simulated Na/Ca mixtures in molar ratios of 10:1 to 20:1. With no Ca, however, damage caused by isosmotic NaCl was 76% to 87% higher, indicating that for these species, the Na: Ca ratio can alter root cell membrane permeability. Correlation between long-term observations in the lysimeters and leakage occurrence in the laboratory indicates that solute leakage tests with roots may aid in characterizing Pistacia spp. rootstocks for saline condition.

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Lie-Bao Han, Gui-Long Song, and Xunzhong Zhang

milligrams chlorophyll per gram W f ( Li, 2000 ). Membrane permeability. Membrane permeability (MP) was determined based on leaf EL (measured as a percentage). The greater the EL value, the higher the MP ( Zhang et al., 2006 ). Fresh leaf blades (300 mg

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Zhengke Zhang, Yu Zhang, Donald J. Huber, Jingping Rao, Yunjing Sun, and Shanshan Li

low-temperature storage (4 °C). The study specifically addressed the effects of inhibition of ethylene action on changes in the oxidant and antioxidant system, including membrane permeability, membrane lipid peroxidation, and activities of prooxidant

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Baomei Yang, Guoliang Li, Shaohai Yang, Zhaohuan He, Changmin Zhou, and Lixian Yao

× N4) × 100/(4 × NT). In the formula, N0–N4 refers to the quantity of fruits in relevant browning grade, and NT corresponds to the overall number of fruits. The measurement of pericarp cell membrane permeability follows the method suggested by Jiang

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Thanidchaya Puthmee, Kenji Takahashi, Midori Sugawara, Rieko Kawamata, Yoshie Motomura, Takashi Nishizawa, Toshiyuki Aikawa, and Wilawan Kumpoun

transpiration rate from the fruit surface associated with incomplete net development, rather than high membrane permeability in the hypodermal tissues. Here, changes in the transpiration rate from the cuticle and net of ‘Life’ fruits were measured separately