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- Author or Editor: Michael R. Boersig x
Abstract
A preparative column consisting of 1 ml each polyvinylpyrrolidone, Amberlite IRA-45 in the acetate form, and Dowex 50W in the acid form removed 98% to 99% of the cations and phenolics from leaf extracts of Euonymus japonica Thunb. and from standard solutions of magnesium acetate and catechin. Sucrose inversion occurred when 2 or 3 ml of cation exchange resin were used or when 1 ml was used at a flow rate of 0.1 ml/min. Sucrose inversion was inversely related to column flow rate.
Methyl bromide (MB) penetration rates, sorption levels, and concentration.time (CT) products were compared in returnable plastic containers (RPCs) and corrugated grape boxes (CGBs). During a 2.5-hour fumigation, sorption of methyl bromide in RPCs and CGBs was 9.8% and 18.1%, respectively. The lower sorption in RPCs increased the exposure of grapes (Vitis vinifera) to MB. Equilibrium concentrations of MB (concentrations that had stabilized) in RPCs and CGBs were 68.2 and 59.2 g·m-3 (4.26 and 3.70 lb/1000 ft3) respectively. The CT products in RPCs and CGBs were 170.5 and 147.6 g·h-1·m-3 (10.66 and 9.19 lb/h/1000 ft3), respectively, and far below phytotoxic concentrations according to the U.S. Department of Agriculture schedule.
Abstract
The extinction point (EP), defined as the lowest O2 concentration at which alcohol production ceases, was a useful concept in early interpretations of the Pasteur effect in fruit. However, ethanol is now known to be a normal constituent of many fruits under aerobic conditions. Therefore, we propose an alternative concept, the anaerobic compensation point (ACP), defined as the O2 concentration at which CO2 evolution is minimum. After 2 to 4 hr under various O2 concentrations, the ACPs of mature-green pears (Pyrus communis L.) and pear cell cultures are 1.6% to 1.7% and 1.1% to 1.3% O2, respectively. The ACP shifts to lower O2 concentrations upon extended exposure of the cells to low-O2 atmospheres and to higher O2 concentrations as pear fruit mature physiologically or as the diffusion coefficient of cell suspensions is decreased. With O2 diffusion coefficients of 4.4, 3.7, and 2.5 × 10−6 cm2·s−1, the ACP effect is observed just below 1.3%, 3.0%, and 5.0% O2, respectively. Analogies between the responses of intact fruit and suspension-cultured cells to limiting O2 are illustrated and use of the latter in assessing the response of pear cells to changing coefficients of diffusion is discussed.