Changes in membrane lipid components and antioxidant levels during natural ageing of seeds of Acer platanoides

Changes in membrane lipid components and cellular antioxidant systems were investigated through 7 years in seeds of Acer platanoides L. after storage in natural conditions, i.e. - 3°C and 10% water content. The loss of germination capacity in aged seeds was associated with increased solute leakage during imbibition, reduced content of phospholipids, especially phosphatidylcholine, and increased free fatty acid content. A marked decrease of unsaturated fatty acids in the phospholipid fraction was observed after one year of storage. Antioxidant potential in the lipid fraction and level of -SH groups decreased during storage. The results are consistent with the hypothesis that ageing in seeds is mediated by a free radical mechanism.     

Reactive oxygen species release, vitamin E, fatty acid and phytosterol contents of artificially aged radish (Raphanus sativus L.) seeds during germination

Seeds of Raphanus sativus L. subjected to accelerated ageing were investigated for reactive oxygen species (ROS) release and for content of vitamin E (tocopherol, TOC, and tocotrienol, TOC-3), fatty acids and phytosterols in seed coats, cotyledons and embryonic axes during germination. In unaged seeds, ROS release occurred mainly in seed coats of non-imbibed seeds and in seedlings (48?h of imbibition). TOC and TOC-3 were mainly represented by the ??-isoform, abundant in embryonic axes. Fatty acids were mainly found in cotyledons. In seed coat and embryonic axis, phytosterols consisted mainly of sitosterols. The effects of ageing were mainly visible in embryonic axes at 48?h of imbibition. Deterioration was associated with a decrease in fresh weight increase percentage, germination percentage, ??-TOC and total fatty acid content. An increase in ROS release from seed coats and in ??-TOC, ??-TOC, ??-TOC-3 content in embryonic axis was also observed. The use of ??-TOC and total fatty acids in embryonic axis as parameters of seed quality evaluation during storage was suggested.     

The Effect of Low Temperature Pre-Sowing Treatment on the Germination Performance and Membrane Integrity of Artificially Aged Tomato Seeds

Loss of seed viability and decrease in germination rate appearto be due to two independent sets of events occurring duringartificial ageing in tomato (Lycopersicon esculentum Mill) seeds.Only the second category of physiological damage is reversible:a low temperature pre-sowing treatment being capable of greatlyreducing the time to fifty percent germination of both unagedand aged seeds, but having no effect on germination capacity.Leakage of ionic solutes from the seeds did not increase followingageing, but there were considerable increases in losses of smallorganic molecules. Low temperature pretreatments did not reducethe rate of loss of either amino acids or reducing sugars fromaged seeds. The implications of the use of artificial ageingin combination with low temperature pre-sowing treatments inthe study of small seed physiology is discussed, as is the valueof solute leakage studies in this kind of seed. Key words: Tomato seeds, Accelerated ageing, Seed treatment, Membranes     

Factors influencing the storability of Fagus sylvatica L. seeds after release from dormancy

Seeds of beech (Fagus sylvatica L.) that have been subjected to dormancy breaking consisting of 10 weeks of prechilling at 3 °C and 34 % water content (WC) and then desiccation to 10 % WC, are non-dormant (ND). ND seeds are characterised by greater sensitivity to storage conditions, than no prechilled, dormant (D) seeds. The aim of the present work was to investigate factors affecting the loss of seed viability during storage of D and ND beech seeds at different temperatures (4 and 20 °C) and humidity levels (45 and 75 % RH) for 3 weeks. In general, both D and ND seeds maintained a high germination capacity after storage at 4 °C. At 20 °C and 45 and 75 % RH the germination capacity of D seeds diminished to 80 and 28 %, respectively. Under the same conditions, ND seeds lost germination capacity to a greater degree, with only 62 and 7 % germinated seeds, respectively. At 20 °C, an increase in production of reactive oxygen species was observed, and the increase was significantly higher in ND seeds. The loss of germination capacity was coincident with an increase in electrolyte leakage and accumulation of free fatty acids, which suggests that membrane deterioration was the cause of the decline in germinability. ND seeds stored at 20 °C and 45 and 75 % RH showed a greater decrease than D seeds in contents of the primary phospholipids phosphatidylcholine (PC) and phosphatidylethanolamine (PE) as well as in polyunsaturated fatty acids (18:2 and 18:3). ND seeds possessed more unsaturated fatty acids, especially 18:3, than D seeds in the phospholipid fraction before storage. D seeds were characterised by a significantly higher level of α-tocopherol and UV-absorbing phenols. The level of ascorbate was similar in D and ND seeds. D seeds contained glutathione in both reduced (GSH) and oxidised (GSSG) forms, and GSSG dominated GSH. ND seeds contained more GSSG form than D seeds. We concluded that the membranes of ND seeds are exposed to greater oxidative stress during storage due to higher levels of unsaturation and lower levels of α-tocopherol, the main antioxidant that protects membranes against free radical attack.     

The effects of desiccation on seeds of Acer saccharinum and Aesculus pavia: recalcitrance in temperate tree seeds

This study was undertaken to determine how the results from lipid, moisture, and differential scanning calorimetry analyses conducted on silver maple (Aceraceae: Acer saccharinum L.) and red buckeye (Hippocastanaceae: Aesculus pavia L.) compared with those obtained from previous studies on white and water oaks (Fagaceae: Quercus alba and Q. nigra), and the tropical zone species American muskwood (Meliaceae: Guarea guidonia) and carapa (Meliaceae: Carapa guianensis). Seeds were air-dried at room temperature for 9-11 days. At intervals, germination was tested, moisture determined, and lipids extracted. It was found that, like the other recalcitrant seeds, (1) viability was greatly reduced or lost after 11 days of drying, (2) percentage changes in individual fatty acids were not related to seed viability, and (3) results from the differential scanning calorimetry studies revealed a strong relationship between enthalpy/onset data from the embryo and cotyledon tissues and loss of viability. Also, silver maple seeds experienced a 50% reduction in viability by day 5 of drying and retained an axis moisture content over 25% throughout the experiment. However, unlike the other recalcitrant seeds surveyed, both silver maple and red buckeye had a significant reduction in the total amount (mg/g) of cotyledon lipids as the experiment progressed. However, no decrease in the unsaturated/saturated fatty acid ratio was found, so we conclude that in these species lipid peroxidation is not a marker of declining seed viability. Also, red buckeye seeds did not lose 50% viability until after day 8 of the experiment, and axis moisture content fell well below 20% as the seeds dried.     

Inter-nucleosomal DNA fragmentation and loss of RNA integrity during seed ageing

The germination of viable seeds is the basis for new plant growth and development. Seeds lose viability during storage, but the biochemical mechanisms of seed death are not fully understood. This study aimed to investigate degradation patterns of nucleic acids during seed ageing and subsequent water uptake. Seeds of Pisum sativum L. were artificially aged at 50°C and 12% seed water content (WC). Nucleic acids degradation was studied during ageing and during imbibition of four seed lots with differential viability from highly viable to dead. As seeds lost viability during ageing, DNA was gradually degraded into internucleosomal fragments, resulting in ‘DNA laddering’, in conjunction with disintegration of 18S and 28S rRNA bands. During imbibition, non-aged controls had high levels of DNA and RNA integrity through to radicle protrusion. In an aged seed lot with 85% total germination (TG) DNA fragmentation decreased upon imbibition probably due to nucleosome degradation, while rRNA integrity did not improve. In an aged seed lot with 44% TG, neither DNA nor rRNA integrity improved upon imbibition. Dead seeds showed DNA degradation as laddering throughout imbibition along with extensive degradation of rRNA. We present a model in which interlinked programmed and non-programmed events contribute to seed ageing, and suggest that protection of nucleic acids during ageing is key to seed longevity.     

Heterologous expression of a fatty acid hydroxylase gene in developing seeds of<Emphasis Type="Italic"> Arabidopsis thaliana</Emphasis>

Expression of a cDNA encoding the castor bean ( Ricinus communis L.) oleate Delta12-hydroxylase in the developing seeds of Arabidopsis thaliana (L.) Heynh. results in the synthesis of four novel hydroxy fatty acids. These have been previously identified as ricinoleic acid (12-hydroxy-octadec- cis-9-enoic acid: 18:1-OH), densipolic acid (12-hydroxy-octadec- cis-9,15-enoic acid: 18:2-OH), lesquerolic acid (14-hydroxy-eicos- cis-11-enoic acid: 20:1-OH) and auricolic acid (14-hydroxy-eicos- cis-11,17-enoic acid: 20:2-OH). Using mutant lines of Arabidopsis that lack the activity of the FAE1 condensing enzyme or FAD3 ER Delta-15-desaturase, we have shown that these enzymes are required for the synthesis of C20 hydroxy fatty acids and polyunsaturated hydroxy fatty acids, respectively. Analysis of the seed fatty acid composition of transformed plants demonstrated a dramatic increase in oleic acid (18:1) levels and a decrease in linoleic acid (18:2) content correlating to the levels of hydroxy fatty acid present in the seed. Plants in which FAD2 (ER Delta12-desaturase) activity was absent showed a decrease in 18:1 content and a slight increase in 18:2 levels corresponding to hydroxy fatty acid content. Expression of the castor hydroxylase protein in yeast indicates that this enzyme has a low level of fatty acid Delta12-desaturase activity. Lipase catalysed 1,3-specific lipolysis of triacylglycerol from transformed plants demonstrated that ricinoleic acid is not excluded from the sn-2 position of triacylglycerol, but is the only hydroxy fatty acid present at this position.     

Relationship between the ATP content measured at three imbibition times and germination of onion seeds during storage at 3, 15 and 30C

The possibility of using ATP content as an indicator of seedquality was studied in onion seeds {Allium cepa cv. Wdenswil).The percentage germination and ATP content of imbibed seedswere compared during 145 weeks of storage at three temperatures(3, 15 and 30C). ATP content, which was undetectable in airdriedseeds (moisture content: 9%, w/w), increased rapidly as a functionof imbibition time, as did the fresh weight and respirationrate, reaching a steady-state level after about 17 h. After36 weeks of storage, the rate of ATP formation was greater forthe seeds stored at 3C than for those kept at 15 and 30C.Furthermore, the onset of ATP synthesis was delayed. These phenomena,which are likely to be an expression of seed ageing, are usefulindicators, allowing the prediction of the loss of seed viabilitybefore the decrease in percentage germination which occurredbeyond 36 weeks of storage. In addition, the correlation betweenATP content and germination capacity of seeds during 145 weeksof storage was excellent (r=0.95 at 15C and 0.97 at 30C),provided that a 17 h-imbibition time, specific for onion seeds,was chosen. These results are discussed in terms of the controversyconcerning the correlation between the ATP content and germinationpercentage of seeds. Key words: Allium cepa, ageing, bioenergetic metabolism, seed quality, temperature storage     

A Comparison of Changes in the Germination Responses and Phospholipid Composition of Naturally and Artificially Aged Tomato Seeds

The changes in germinability and phospholipid content of naturallyand artificially aged tomato seeds, variety Kingley Cross, werecompared. Subsequent low temperature pre-sowing treatment (LTPST)was unable to prevent decreases in the germination capacityof aged samples, but significantly improved germination rates.However, in contrast to previous studies on artificial ageingusing the variety Moneymaker, losses of total phospholipid werenot always well correlated with decreased germinability. Totalphospholipid levels in naturally aged seeds were largely unaffectedby pre-sowing treatment, but the proportion of phosphatidylcholinewas greatly increased. These results strongly suggest that lossesof phospholipid are coincidental rather than causative eventsin the loss of seed viability during ageing, and that the patternof changes depends on the type of ageing experienced by theseeds. Controlled deterioration, seed ageing, tomato seeds, seed treatment, phospholipids     

Organization of lipid reserves in cotyledons of primed and aged sunflower seeds

Imbibing sunflower (Helianthus annuus L., cv. Briosol) seeds at water potentials between –2 MPa and –5 MPa leads to faster (priming) or slower (accelerated ageing) germination depending on the temperature and duration of treatment. Mobilization of food reserves may be associated with the changes in seed vigor. To study this, morphological, biochemical and phase properties of lipid, the major food reserve in sunflower, were compared in freshly harvested (i.e., control), primed and aged sunflower cotyledons using electron microscopy, biochemical analyses and differential scanning calorimetry, respectively. Lipid bodies became smaller and more dispersed throughout the cytoplasm during priming and ageing. Despite ultrastructural changes, there were few measured changes in biochemistry of the neutral lipid component; lipid content, proportion of saturated and unsaturated fatty acids and level of free fatty acids were unchanged in primed and slightly aged seeds, with only severely aged seeds showing a net decrease in polyunsaturated fatty acids and an increase in free fatty acids. Subtle changes in the calorimetric behavior of lipids within sunflower cotyledons were observed. Sunflower lipids exhibited polymorphic crystalline and amorphous solid phases when cooled to <–100°C, but priming decreased the rate of crystallization in vivo and ageing increased the rate of crystallization, but decreased percentage crystallinity. The observed changes in thermal behavior in vivo are consistent with losses and gains, respectively, of interacting non-lipid moieties in the triacylglycerol matrix.     

The Effect of Low Temperature during Imbibition on Germination Characteristics of Tetracentron sinense (Tetracentraceae) Seeds

In this paper, the effects of low temperature, soil moisture and freezing time on the germination of Tetracentron sinense Oliv. seeds were studied by simulating wild environment conditions, and the factors influencing the natural regeneration of Tsinense population were discussed. The results are as follows: (1) The imbibition process of Tsinense seed can be divided into four stages, the water absorbing capacity of Tsinense seed after imbibition would increase with the increase of soil moisture, and the seeds would be fully imbibed under the condition of 30% soil moisture; (2) The germination rate, germination force and water content of Tsinense seed increased with the increase of storage time, and the vigor index gradually decreased after increasing before; (3) At different low temperature, the germination rate of Tsinense seed reached the highest when the soil moisture is 20% or 30%; (4) When treated at 20% soil moisture for 2-4 days or 21-28 days, 0℃ is best for the germination rate of Tsinense seed; when treated at 30% soil moisture for 14-28 days, -7℃ is best fort he germination rate of Tsinense seed; (5) When treated at the same condition of freezing time, the germination rate of seeds in fallen leaves had no significant difference with the decrease of low temperature; under the same condition of low temperature (0℃ low temperature except), the germination rate increased after frozen 28 days. The results showed that there is no significant influence of low temperature during imbibition on germination characteristics of Tetracentron sinense seeds and indicating that low temperature during imbibition is not the main factor influencing the natural regeneration of Tsinense population.     

Ischemia-Induced Changes in Cerebral Mitochondrial Free Fatty Acids, Phospholipids, and Respiration in the Rat

Abstract: Changes in the free fatty acid pool size and fatty acyl chain composition of mitochondrial membrane phospholipids and their relation to disruption of mitochondrial function were examined in rat brains after 30 min of cerebral ischemia (Pulsinelli-Brierley model) and 60 min of normoxic reoxygenation. During ischemia, significant hydrolysis of polyunsaturated molecular species from diacyl phosphatidylcholine, particularly fatty acyl 20:4 (arachidonic acid; 20% decrease) and 22:6 (docosahexaenoic acid; 15% decrease), was observed. Thirty minutes of ischemia caused a 16% loss of 18:2 (linoleic acid) from phosphatidylethanolamine. Recirculation for 60 min did not return the polyunsaturated fatty acid content of phospholipids to normal. Total content of free fatty acids increased during ischemia, particularly 18:2 and 22:6, which exhibited the most dramatic rise. The free fatty acid pool size continued to increase during 60 min of recirculation. The respiratory control ratio decreased significantly during 30 min of ischemia with no apparent recovery following 60 min of reoxygenation. The degree of free radical-mediated lipid peroxidation in mitochondria was significantly increased during ischemia and reperfusion. It was concluded that (a) 30 min of cerebral ischemia caused differential degradation in each of the phospholipid classes and preferential hydrolysis of the polyunsaturated molecular species and (b) 60 min of normoxic reperfusion failed to promote reacylation of the mitochondrial phospholipids and restoration of normal respiration.     

Effects of dietary butter enrichment on the fatty acid distribution of phospholipid fractions isolated from rat platelets and aortae

Rats were maintained for 2 weeks on a low-fat basal diet (5% energy) and a diet from which 50% of the energy was derived from butter. Lipids were extracted from aortae and platelets and the fatty acid profiles of individual phospholipids were examined. Similar responses to dietary butter enrichment occurred in PI, PS, PE and PC fractions from either tissue: 20:4(n - 6) and all other n - 6 series longer-chain polyunsaturated fatty acids except 20:3(n - 6) decreased in percentage; all n - 3 series polyunsaturated fatty acids increased, including 20:5(n - 3) and 22:6(n - 3); n - 9 series polyunsaturated fatty acids, derived from 18:1(n - 9), increased. Despite the considerable redistribution of polyunsaturated fatty acids, the percentages of total polyunsaturated fatty acids in each phospholipid were, in every case, independent of diet. None of the changes were localized in a particular phospholipid fraction. Quantitation of fatty acids using heptadecanoic acid as an internal standard revealed that the concentrations of 20:4(n - 6) in platelet and aortic PE and PC was higher than in PI fractions. Therefore, in terms of substrate amount, it appears that PC and PE as well as PI have the potential to provide endogenous 20:4(n - 6) for oxygenation to the prostanoids thromboxane A2 and prostacyclin I2.     

Comparison of phospholipid and fatty acid composition of wild and cultured striped bass eggs

The dominant fatty acids in all neutral lipid fractions of non-water hardened eggs from two wild and one cultured stock of striped bass Morone saxatilis were the monoenes, 18 : 1n9/n7>16 : 1n7>17 : 1. The dominant fatty acids in the phospholipid fraction of all eggs, regardless of origin, were 22 : 6n3>18 : 1n9/n7>20 : 5n3>16 : 1n7>16 : 0>18 : 0. Arachadonic acid (AA, 20 : 4n6) was significantly lower (2·0%) in cultured fish eggs compared to either wild stock (5·8–6·1%). Fatty acids from the liver and eggs of wild Shubenacadie fish were similar to one another with respect to both neutral and phospholipid fractions. However, the AA and eicosapentaenoic acid (EPA, 20 : 5n3) content of the phospholipid fraction varied according to the hypothesized migration behaviour of Shubenacadie fish. The total lipid content of wild fish eggs was significantly greater than that of cultured fish. The total phospholipid content of Shubenacadie eggs was significantly higher than either Roanoke or cultured fish eggs. Phosphotidylinositol (PI) was the dominant phospholipid found ins all egg samples from all origins as opposed to phosphotidylcholine, which is usually the dominant phospholipid. These data indicate that PI and AA may have important and as yet unidentified roles in fertilization and embryonic development in these fish.     

Seasonal changes in lipid classes and fatty acid composition in the digestive gland of Pecten maximus

Seasonal variations in lipid classes and fatty acid composition of triacylglycerols and phospholipids in the digestive gland of Pecten maximus were studied over a period of 16 months. Acylglycerols predominated (19-77% of total lipids), in accordance with the role of the digestive gland as an organ for lipid storage in scallops. Seasonal variations were mainly seen in the acylglycerol content, while phospholipids (2.5-10.0% of total lipids) and sterols (1.9-7.4% of total lipids) showed only minor changes. The most abundant fatty acids were 14:0, 16:0, 18:0, 16:1(n-7), 18:1(n-9), 18:1(n-7), 18:4(n-3), 20:5(n-3) and 22:6(n-3) and these showed similar seasonal profiles in both, triacylglycerol and phospholipid fractions. In contrast to the phospholipid fraction, the triacylglycerol fraction contained more 20:5(n-3) than 22:6(n-3). In three phospholipid samples we noted a high percentage of a 22-2-non-methylene-interrupted fatty acid, previously described to have a structural role in several bivalve species. The main polyunsaturated fatty acids displayed important seasonal variations parallel to those of the acylglycerols, suggesting good nutritional conditions. A positive correlation existed between the level of saturated fatty acids and temperature, whereas the levels of polyunsaturated fatty acids correlated negatively with temperature.     

The influence of acclimation temperature on the lipid composition of the larval lamprey, Petromyzon marinus, depends on tissue and lipid class

This study was designed to examine the effect of thermal acclimation on the lipid composition of fat depot organs the liver and kidneys of larval sea lamprey, Petromyzon marinus. We found that 21 °C-acclimated larvae possessed lower total lipid amounts in the liver (39% lower) and kidneys (30% lower) than 13 °C-acclimated larvae. Relatively lower lipid contents in the liver and kidneys of 21 °C-acclimated lamprey primarily resulted from a reduction in stored lipid reserve, triacylglycerol, but not the structural lipid, phospholipid. Compared to 21 °C-acclimated larvae, 13 °C-acclimated larvae were found to possess fewer saturated fatty acids (SFAs) and more unsaturated fatty acids (USFAs) in renal triacylglycerol and phospholipid classes, while there were no significant differences in the SFAs and USFAs of hepatic triacylglycerol, phospholipid, cholesteryl ester, fatty acid, and monoacylglycerol classes. Fewer SFAs, found in the kidney triacylglycerol of 13 °C-acclimated lamprey, were due to lower 12:0 and 14:0 fatty acids, but those in the renal phospholipid class were characterized by fewer 14:0, 15:0, and 16:0 fatty acids. More USFAs in renal triacylglycerol, as indicated by a higher unsaturation index, primarily resulted from higher polyunsaturated fatty acids (18:2ω6, 18:3ω3, and 18:4ω3); whereas, in the renal phospholipid class, this was a result of higher monoenes (18:1, 20:1, and 22:1ω9) and ω3 polyunsaturated fatty acids (18:4ω3). These data suggest that the influence of thermal acclimation on the lipid composition of lamprey fat depot organs depends on tissue and lipid class.     

Germination and Food Reserves in Bambarra Groundnut Seeds (Voandzeia subterranea Thouars) after Different Periods of Storage

Studies were made on bambarranut seeds (Voandzeia subterraneaThouars) after 0, 6, 12, 18 and 24 months of storage in gunnybags under laboratory conditions (25–35 °C). Seeddeterioration during storage was indicated by delayed germination,reduced germinability, reduced growth of seedlings and increasednumber of stunted seedlings culminating in a total failure ofgermination after two years. Slight depletion of food reserves occurred during seed storage.The loss in fat was higher than starch or protein. Total solublesugars decreased while the content of total fatty acids andamino acids and soluble protein increased. Total nitrogen (N)remained unaffected while soluble-N and amino-N increased. Allthese components showed a rapid change (increase or decrease)from 12 months to 18 months of storage which was associatedwith commencement of rapid decline in germinability of the seedsand growth of the seedlings. Initial rapid imbibition of water was observed in viable aswell as non-viable seeds, though at a higher rate in the latterand followed by a lag period in both. At the end of 24 h ofimbibition, water content in non-viable seeds was less thanthat in viable ones. Key words: Voandzeia subterranea, Seed germination, Seed storage     

The effect of n-3 fatty acids on osmotic fragility of rat erythrocytes

In order to study the effect of n-3 fatty acids on the physical state of the erythrocyte membrane, measured as osmotic fragility, rats were fed a diet supplemented in n-3 fatty acids (1.5 ml/day, 35% 20:5, 30% 22:6) for 21 days. With salt concentrations ranging from 0.37% to 0.44%, osmotic resistance was increased by 25% to 45% in cells from n-3-fed animals compared to controls. No change was observed in either phospholipid or cholesterol content in the membrane. A small, but still significant difference (P less than 0.05) in phospholipid sub-class distribution was observed in that the phosphatidylethanolamine fraction was decreased and the phosphatidylserine fraction increased after n-3 supplementation. The major change was, however, that the level of eicosapentaenoic acid (20:5(n-3] in phospholipids was increased from 1.5% of total fatty acids to 4.5%. This increase was mainly at the expense of linoleic acid (18:2(n-6]. No change was observed in the level of docosahexaenoic acid (22:6(n-3]. It is thus concluded that both the fatty acid composition and the nature of the phospholipid polar head group may influence the osmotic fragility of erythrocytes.     

Changes in myocardial lipid composition during surgery with cold and chemical cardioplegia

The changes of children myocardium lipid composition were studied for the first time during surgical intervention under cold crystalloid cardioplegia. The surgical intervention was performed as a result of congenital heart disease--atrial septal defect. It was shown that the quantity of short chain fatty acids decreased and the amount of long chain fatty acids increased in the content of phospholipid fraction. Simultaneously the amount of linoleic (C18:2 omega 6), of docosahexaenoic (C22:6 omega 3) and of some other fatty acids decreased in the content of cholesterol esthers. The accumulation of free linoleic (C18:2 omega:6), (C18:2 omega:4) and linolenic (C18:3 omega:6) acids was found. Reperfusion caused the additional changes of myocardium lipid composition. The amount of palmitic (C16:0) acid decreased by 30%. The quantity of some other saturated free fatty acids also diminished. Simultaneously the content of free oleic (C18:1 omega 9) also decreased as a consequence of lipid peroxidative processes activation. The ratio of omega 6/omega 3 increased during the few first minutes of reperfusion in the fraction of free fatty acids and cholesterol esthers.     

Lipid biosynthesis in seeds of mustard (Brassica juncea) influenced by zinc and sulphur deficiency

In developing seeds of mustard ( Brassica juncea L. cv. RLM 198) the period between 20 and 30 days after fertilization (DAF) was identified as the period of active lipid biosynthesis, although dry matter continued to accumulate until maturity. The period of lipid synthesis was associated with a decrease in starch, soluble sugars and protein, thus, giving rise to precursors for the biosynthesis of lipids. Besides decreasing the dry matter content (on both % and seed basis), Zn and S deficiency caused a significant ( P > 0.05) reduction in oil content. As compared to control, the decrease in oil content was 11, 12 and 18% at 30 DAF and 4, 9 and 16% at maturity in Zn, S and (Zn+S) deficient treatments, respectively. Throughout the period of seed development, a significant decrease in starch and protein with a slight accumulation of soluble sugars was observed due to deficiency of Zn or S. The rate of [l-¹⁴C]-acetate incorporation into total lipids, which was maximal at 30 DAF, also displayed a significant decrease due to the abovementioned mineral deficiencies. Addition of Zn or S in vitro, enhanced the lipid synthesis at all stages of seed development. Under Zn and S deficiency, the phospholipids increased from 10 to 30 DAF and then declined until maturity. However, the proportion of glycolipids and free fatty acids increased, with a corresponding decrease in total glycerides. Further, in deficiency treatments, there was an increase in 22:1 with a corresponding decrease in 18:1, 18:2 and 18:3 in developing and mature mustard seeds.