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Shiow Y. Wang and Miklos Faust

Composition changes in galactolipids, phospholipids, and sterols in apple shoots (Malus domestica Borkh. cv. Red Delicious) from August to April were determined. The predominant fatty acids in the membrane lipids of apple shoots were palmitic acid (C16:0), linoleic acid (C18:2), and linolenic acid (C18:3). The major galactolipid components in apple shoots were monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG). The amount of MGDG and DGDG increased from autumn to spring. Galactolipids contained highly unsaturated fatty adds, mainly linoleic (18:2) and linolenic (18:3) acid. The major individual phospholipids were phosphatidylcholine (PC) and phosphatidylethaeolamine (PE). β -Sitosterol and sitosteryl ester were the predominant sterols. The phloem contained higher amounts of galactolipids, phospholipids, and sterols than did the xylem tissue. There was a significant increase in the content of galactolipids and phospholipids and onsaturation of their fatty acids during cold acclimation. A decrease in the ratio of free sterols to phospholipids also occurred in apple shoots toward cold winter months. Composition changes in galactolipids, phospholipids, and sterols that were associated with growth cessation, defoliation and cold acclimation from fall to winter, were mostly reversed following deacclimation in spring.

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Shiow Y. Wang and Miklos Faust

The changes of membrane lipids in apple (Malus domestics Borkh. cv. Delicious) auxillary and terminal buds from August to April were determined. The predominant lipids were monogalactosyl diglyceride (MGDG), digalactosyl diglyceride (DGDG), phosphatidylcholine (PC), and phosphatidylethanolamine (PE). An increase in membrane polar lipids was associated with budbreak and bud growth from August to April. Linolenic acid was the predominant fatty acid in MGDG, DGDG, and PC, while linoleic acid was predominant in PE. Phosphatidylglycerol (PG) and phosphatidylinositol (PI) contained a high amount of palmitic acid. The ratio of (18:2 + 18:3) to 18:1 fatty acids in galactolipids in apple buds increased from August to April. ß-Sitosterol and sitosteryl ester were the predominant sterols in apple buds. An increase in sitosterol, a decrease in sitosteryl ester, and a decline in the ratio of free sterols to phospholipids occurred during budbreak in spring. A decrease in sitosterol was associated with bud expansion in spring.

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Kemin Su, Dale J. Bremer, Richard Jeannotte, Ruth Welti, and Celeste Yang

molecular species in cellular membranes may change in response to environmental stress ( Grover et al., 2000 ; Welti et al., 2002 ). The major categories of plant cellular membrane lipids are glycolipids and phospholipids ( Lea and Leegood, 1993

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Shiow Y. Wang and Miklos Faust

The glycolipids, phospholipids, and sterols were determined in normal and watercore-affected apple (Malus domestica Borkh. cv. Delicious). Fruit with watercore contained higher amounts of glycolipids, phospholipids, and sterols. The ratios of unsaturated to saturated fatty acids and (18:3) to (18:1 + 18:2) were lower in watercore-affected tissue than in normal tissue. The ratio of free sterols to phospholipids was higher, whereas the ratio of phosphatidylcholine to phosphatidylethanolamine was lower in watercore-affected apple. Membrane lipids were altered in watercore-affected fruit.

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Chana Phromtons and J. O. Garner Jr.

Storage roots of `Beauregard' and Centennial' were analyzed for total fatty acid composition and fatty acid composition by lipid class. The glycolipid, monagalactosyldiglycerol, may have been involved in chilling tolerance of `Beauregard' storage roots. This lipid had over 70 percent low-melting point fatty acids, mostly linoleic acid and linolenic acid. No consistent differences in the composition of phospholipids could be related to the chilling responses of the two sweetpotato cultivars.

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James Q. Garner Jr. and Thammasak Thongket

Proline content, leaf water potential (LWP), and leaf diffusive resistance (LDR) were determined for eight sweetpotato genotypes underwater stress conditions. Changes in fatty acid compositions of leaf polar lipids were determined in two sweetpotato genotypes during declining soil moisture. Proline did not accumulate and LWP did not decrease until soil moisture dropped below 10%, but LDR increased as soil moisture decreased. Genotypic differences in proline accumulation and LWP were found. Changes in fatty acid compositions occurred more in glycolipids than in phospholipids. Fatty acid changes were more pronouned in genotype MS20-2 than in “Vardaman”

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Bruce D. Whitaker

Abbreviations: ASG, acylated steryl glycoside; DGDG, digalactosyldiacylglycerol; FS, free sterols; GL, galactolipids; GlyL, glycolipid; MGDG, monoga-lactosyldiacylglycerol; NL, neutral lipid; PA, phosphatidic acid; PC, phosphatidylcholine; PE

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Dana F. Faubion and Adel A. Kader

California-grown `Hass' avocado fruit were stored at 5C, in air or a controlled atmosphere (CA) of 2% oxygen and 5% carbon dioxide. Fruit were evaluated at 0, 2, 4, 6, 8, 10, and 12 weeks, both immediately upon removal from storage and after ripening at 20C. Severe chilling injury (flesh browning) developed in the airstored fruit after 6 weeks, while only moderate symptoms were observed in CA-stored avocado fruit after 12 weeks. Lipid peroxidation breakdown products increased during storage and ripening in both air and CA treatments. Sterols, steryl esters, steryl glycosides, glycolipids, and phospholipids were analyzed. Quantity of acylated steryl glycoside in ripe fruit changed from 34 nmoles initially, to 51 or 27 nmoles after 6 weeks at 5C in air or CA, respectively. Glycolipid fatty acid unsaturation in air-stored fruit decreased with the development of chilling injury. Fatty acid unsaturation in phospholipids (phosphatidylinositol, phosphatidylcholine, phosphatidylglycerol, and phosphatidylethanolamine) of air-stored avocados decreased with the development of chilling injury. CA storage delayed the development of chilling injury and the loss of fatty acid unsaturation.

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Arambage Abesinghe and James O. Garner

Storage roots of `Beauregard' and `Centennial' were used to identify varietal differences in fatty acid composition in plasmalemma lipids during storage conditions. Total plasmalemma fatty acid composition of glycolipids and phospholipids in storage roots of `Beauregard' and `Centennial' did not differ. The fatty acid composition of MGDG and DGDG in storage root plasmalemma was >50% unsaturated fatty acids in `Beauregard'. The high percentage of 18:2 (65.44%) fatty acid compared to `Centennial' (19.70%) and 79.35% total unsaturated fatty acid content in MGDG may contribute to low temperature tolerance in `Beauregard'. The higher percentages of 16:1 and 22:1 fatty acids in `Centennial' compared to `Beauregard' contributed to MGDG fatty acid unsaturation. However, these fatty acids have not been related to chilling tolerance.

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Dana F. Faubion and Adel A. Kader

California grown `Hass' avocado fruit were stored at 5C, in air or a controlled atmosphere (CA) of 2% oxygen and 5% carbon dioxide. Fruit were evaluated at 0, 3, 6, and 10 weeks, both immediately upon removal from storage and after 5 days at 20C. Severe chilling injury developed in the air-stored fruit after six weeks, while only moderate symptoms were observed in CA stored avocado fruit after 10 weeks. Lipid peroxidation breakdown products increased during storage and ripening in both air and CA treatments. Sterols, sterol esters, glycolipids, and phospholipids were analyzed. There was a shift in composition during storage towards increasingly saturated fatty acids. The fatty acid shift was greater in air, than in CA stored fruit. Results will be discussed concerning their relevance to chilling injury development.