Mojtaba Massoudi is gratefully acknowledged for his technical assistance in lipid analysis. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby
Pollen from five cultivars (cvs.) of pecans [Carya illinoinensis (Wangenh.) K. Koch] was sampled at Brownwood and College Station, Texas, in 1991 and 1992. Samples were analyzed for cytoplasmic lipid classes and constituent fatty acids. Lipid classes in all cvs. included phosphatidyl inasitol, phosphatidyl swine, phosphatidyl choline, phosphatidyl glycerol, phosphatidyl ethanolamine, free fatty acids, and triglycerides. Triglycerides were the predominant class of lipids in all cvs. analyzed. Fatty acids, qualitated and quantitated by gas chromatographic-mass spectral analysis, included palmitie (16:0), stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic (18:3) adds. Quantities of individual and total fatty acids were significantly influenced (P> 0.05) by tree age. Within a uniform age class, quantities of individual and total fatty acids varied greatly and were significantly influenced by cultivar, year, and location as well as by interactions of main effects. The percent composition of individual fatty acids was stable in relation to total fatty acids in the sample, despite wide variation in quantities of fatty acids in different samples. Total fatty acids varied from 2.53% to 0.25% of dry weight. How this large variability in stored energy levels among pollen sources may affect orchard production is discussed.
Pollen from five cultivars of pecans [Carya illinoinensis (Wangenh.) K. Koch] was analyzed for cytoplasmic lipid classes and constituent fatty acids. Lipid classes in all cultivars included free fatty acids, triglycerides, and the phosphatide of inositol, serine, choline, glycerol, and ethanolamine. Triglycerides were the predominant class of lipids in all cultivars analyzed. Gas chromatography and mass spectral analysis were used to identify and quantify the fatty acids, which included palmitic, stearic, oleic, linoleic, and linolenic. Quantities of individual and total fatty acids varied greatly and were influenced significantly by cultivar, year, and location, as well as by interactions of main effects The percent composition of individual fatty acids was remarkably stable, despite wide variation in quantities of fatty acids. Therefore, pollen fatty acid ratios may be a valuable measure of taxonomic relationship across Carya sp. Total fatty acids varied from 2.53% to 0.25% of dry weight. Variability in stored energy in the form of lipids may affect orchard production.
Altered metabolism of membrane lipids has been proposed as a mechanism for the beneficial effects of postharvest calcium treatment on apple quality. A previous study showed that after transfer of apples stored 6 months at 0C to 20C, calcium-treated fruit exhibited slower loss of galactolipid and altered levels of sterol conjugates. The present study of lipids in “control” fruit was conducted as a prelude to further in-depth analyses of the effects of postharvest calcium and heat treatments on lipid metabolism in apples during and after cold storage. Neutral lipid, glycolipid (GL), and phospholipid (PL) fractions were obtained by column chromatography followed by TLC separation of GL and PL classes. The major GL were steryl glycosides (SG), acylated steryl glycosides (ASG), cerebrosides (CB), and mono- and digalactosyl diacylglycerols. Phosphatidylcholine (PC) > P-ethanolamine (PE) > P-irositol (PI) were the major PL. The fatty acids of PC and PE were quite similar, whereas those of PI were more saturated. CB included only 2-hydroxy fatty acids. Among the steryl lipids, free sterols > SG > ASG, with beta-sitosterol >90% of the total sterol in each.
Abscission is a natural plant process that culminates in the removal of organs from the parent plant. Control of abscission remains an important goal of agriculture, but events that initiate and transduce abscission signals have not been well defined. An understanding of these events may reveal pathways that can be targeted to control abscission. The compound 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) is a pyrazole-derivative that induces abscission selectively in mature citrus (Citrus sinensis) fruit when applied to the canopy. Peel contact is essential for efficacy. Previous work identified CMNP as an uncoupler. Timing of CMNP-induced events in citrus flavedo indicated that increased reactive oxygen species and electrolyte leakage occurred within 30 minutes and 2 hours after application, whereas reduced ATP content was measured 3 hours after application. Phospholipase A2 (PLA2) and lipoxygenase (LOX) activities, and lipid hydroperoxide (LPO) levels increased in flavedo of citrus fruit peel treated with CMNP, indicating that the lipid signaling pathway was activated. A specific inhibitor of PLA2 activity, aristolochic acid (AT), reduced CMNP-induced increases in PLA2 and LOX activities and LPO levels in citrus flavedo and greatly reduced abscission, suggesting that production of phospholipid-derived signals influence abscission process. However, AT treatment failed to halt the reduction in ATP content, indicating that reduction in ATP preceded the increase in PLA2 activity and the biological response. The results demonstrate a link between lipid signaling and abscission in citrus.
Postharvest heat treatment of apples maintains fruit firmness and reduces decay during storage. Four days at 38C are beneficial, but 1 or 2 days are detrimental. The cellular basis of these effects may involve changes in cell wall and membrane lipid metabolism. Lipids from hypodermal tissue of `Golden Delicious' apples were analyzed after 0, 1, 2, or 4 days at 38C. Major lipids included phospholipids (PL), free sterols (FS), steryl glycosides (SG), and cerebrosides (CB). Galactolipids (GL) were minor components. PL content fell ?10% after 1 day at 38C, was unchanged after 2 days, and began to rise again after 4 days. PL class composition did not change with heating, but fatty-acid unsaturation declined throughout. FS and CB content and composition changed little, whereas SG content cropped by ≈20% over 4 days. GL fell ≈50% during 1 day at 38C, with no change at days 2 or 4. A burst of PL catabolism followed by recovery of synthesis may in part explain the different effects of 1-, 2-, or 4-day heat treatments. GL loss (in plastids) may be related to the effect of heat on fruit color (yellowing).
A previous study of lipids from pericarp tissue of tomato fruit ranging from mature-green to red-ripe showed a large increase in total sterols accompanied by dramatic changes in sterol composition and conjugation with ripening. This study was conducted to determine whether similar changes occur in microsomal membranes derived from tomato fruit pericarp. Acylated steryl glycoside (ASG), the predominant steryl lipid, declined during ripening, with increases in steryl glycoside (SG) and free sterol (FS). Only minor changes in fatty acid composition were associated with the drop in ASG. The stigmasterol:sitosterol ratio increased throughout ripening, but much more in Fs than in SG or ASG. The ratio of FS to phospholipid (PL) increased with ripening. However, FS was never greater than 10 percent of the total membrane sterol (TMS), and TMS:PL actually declined over the middle stages of ripening. It is not known why tomato tissues maintain such high levels of ASG and SG, but sterol conjugation is thought to regulate the physical properties of cell membranes.
Carrot has been bred for increased levels of pro-vitamin E α-tocopherol. This vitamin is lipid soluble. Carrot root has been shown to have measurable levels of lipid, but it is not certain if the lipid level is correlated to α-tocopherol levels. The HPLC method is needed to quantify levels of α-tocopherol. Measuring lipids may be less time consuming in a breeding program. We developed a method for extracting lipids from carrot tissue based on the Soxhlet extraction method. The Soxhlet extraction uses a non-polar ether solvent to pull lipids out of freeze-dried tissue. A collection of carrot accessions ranging in α-tocopherol concentration 0.04–0.18 ppm and carotenoid concentration 10.63–1673.76 ppm were used in this investigation. Root tissue was freeze-dried and lipid levels were measured in an experiment with two replications. The mean lipid level of root tissue was 0.05 g fat/g tissue. The range was 0–1.1 g fat/g tissue. Phenotypic correlations were performed among lipid, α-tocopherol, and β-carotene concentrations in these samples. Twenty-four samples were tested for lipid levels (12 high and 12 low). From these results, percent lipid of the root was determined. Correlations were made between the lipid data and α-tocopherol data of the given samples.
using store-bought ‘Hass’ as the standard. Attributes assessed included dry matter and lipid content to determine whether these hybrids would meet California standards for avocado maturity when grown in east-central Florida. Materials and Methods Fruit
Plasmalemma lipid fatty acid changes due to low temperature (12C) were observed in M521-1 and `Travis', chilling-tolerant and -sensitive, respectively, genotypes. Lipid fatty acid changes found in both genotypes after exposure to chilling included decreased palmitic acid (16:0) and an increased unsaturated: saturated fatty acid ratio. Changes detected only in the tolerant genotype were increased linoleic (18:2), linolenic (18:3) and erucic (22:1). Monogalactosyldiglyceride and phosphatidylglycerol were the only lipids with >50% of their fatty acids unsaturated; therefore, it was concluded that these lipids were involved in the chilling tolerance of M521-1. A reduction in arachidonic (20:4) on phosphatidylinositol from `Travis' exposed to 12C resulted in <50% unsaturation of this lipid. This change could be associated with the chilling sensitive response of `Travis'.