Leaf Lipid Composition Research Articles

Fatty acid composition of leaf lipids of some <i>Alchemilla</i> L (Rosaceae) species from Northeast Anatolia (Turkey)

Fatty acid composition of total leaf lipids of 23 species from five series of the genus Alchemilla L. was studied by GC. Fatty acids identified and quantified are C 12:0, C 14:0, G 16:0, G 18:0, G 20:0, G 22:0, G 24:0, G 26:0 and G 28:0 as saturated, and G 16:1, G 18:1, G 18:2 and G 18:3 as unsaturated with the major fatty acids G 18:2 and G 18:3. The highest content of fatty acid was quantified in A. hirtipedicellata (78.34%) for ser. Elatae, A. A.erytropoda (68.74 %) for ser. Pubescentes, A. rizensis (76.47%) for ser. Sericeae, A. dura (73.94%) for ser. Galycinae and A. psedocartalinica (74.58%) for ser. Vulgares. The G 18:1 acid was determined in trace amounts while G 20:0, G 22:0, G 24:0 and G 28:0 acids were not determined in most of these species. Taxonomic value and phylogenetic implications of results are discussed.

Seasonal changes in leaf lipid and fatty acid composition of nine plants consumed by two African herbivores.

In the wild, nutrients from plants provide for the requirements of all herbivores and ultimately all animals, yet little work has been published on how such nutrients change with environmental conditions. Plant lipids are nutritionally important for browsing mammals, initially with respect to taste and palatability, but ultimately how they fulfill a variety of functions. This study reports on seasonal changes in fatty acid (FA) profiles of nine plants commonly consumed by two herbivore species (kudu and impala) in South Africa. The FA composition of the plants varied with both season and plant species but not with geographic location. The overall profile of FA provided a maximum of n-3-essential FA during the transition and wet seasons, but there was no parallel increase in n-6-essential FA.

Effects of canopy shade on the lipid composition of soybean leaves

The effect of canopy shade on leaf lipid composition was examined in soybeans (Glycine max cv. Young) grown under field conditions. Expanding leaves were tagged at 50, 58 and 65 days after planting (DAP) in plots with either a high (10 plants m−1 row) or low (1 plant m−1 row) plant density. At 92 DAP, light conditions ranged from a pho‐tosynthetic photon flux density (PPFD) of 87% of full sun with a far‐red/red (735 nm/645 nm) ratio of 0.9 at upper canopy leaves to extreme shade where the PPFD was 10% of full sun with a far‐red/red ratio greater than 6. Highly shaded leaves in the high plant density treatment accumulated triacylglycerol (TG) up to 25% of total leaf lipid, a 2.4‐fold increase in TG on a chlorophyll basis compared to leaves in the upper canopy. Although total polar lipid content was reduced up to 50% in shaded leaves, shade had little affect on the lipid content or composition of thylakoid membranes. Shade did not affect leaf chlorophyll content. Therefore, the changes in leaf lipid composition were not related to senescence. These findings suggest that conditions of low irradiance and/or a high FR/R ratio cause a shift in carbon metabolism toward the accumulation of TG, a storage lipid. Eighteen‐carbon fatty acid desaturation was also affected in highly shaded leaves where a reduction in linolenic acid (18:3) content was accompanied by a proportional increase in oleic (18:1) and linoleic (18:2) acids.

A Quantitative Evaluation of the Lipid Composition of Leaves of Aleurites montana as a Consequence of Growth under 0.3 ppm SO2 in the Atmosphere

Abstract Gassing during 14 days of Aleurites plants with 0.3 ppm SO2 leads to quantitative modifications of the lipid composition of leaves. The ratio of phospholipids to glycolipids is shifted from 1:3 in control plants to 1:1.8 in SO2-plants. Glycolipids decrease from 62% of total lipids in control plants to 50% in SO2-plants. On the other hand phospholipids increase from 20% in control plants to 28% of total lipids in SO2-plants. This implies that not only the thylakoid membrane but also the mitochondrial membranes and cell membranes of tonoplasts and of the plasmalemma suffer modifications under the influence of SO2. With respect to the fatty acid composition, despite the drastic change in the lipid composition no alteration in comparison to control plants is seen. Chlorophylls increase in SO2-plants by 24% . Also the content of β-carotene, and of the xanthophylls lutein, violaxanthin and neoxanthin is increased. Only zeaxanthin exhibits a decrease. From the changes in the chlorophyll and carotenoid content it can be concluded that in SO2-plants the light-harvesting-complex (LHCP) is stronger developed (P. He, A. Radunz, K. P. Bader and G. H. Schmid, Z. f. Naturforsch. 51c, 441- 453 and 833-840, 1996).

Leaf membrane lipids and drought tolerance in young coconut palms ( Cocos nucifera L.)

The dehydration tolerance of leaf membranes of three coconut palm (Cocos nucifera L.) cultivars with different levels of resistance to drought stress in the field was evaluated by analysis of membrane lipids. Young plants, grown singly in pots, were subjected to controlled dehydration by witholding watering. The composition of coconut leaf lipids was similar to that of higher plants of the so-called ‘18:3 (α-linolenic)’ group, although the total lipid content was lower than that of herbaceous tropical crops. In response to drought stress, leaf total lipid and chloroplastic major lipid (monogalactosyl diacylglycerol) contents decreased more markedly in the more drought-susceptible cultivars. Analysis of leaf lipids is thus proposed as an early screening test for tolerance to drought stress. Despite the decrease in lipid contents, no modification of the fatty acid composition of total lipid extract and of monogalactosyl diacylglycerol was revealed, suggesting a high membrane tolerance to desiccation in Cocos. The fatty acid composition of the major phospholipid (phosphatidylcholine) was markedly enriched in α-linolenic acid in response to water deficit, suggesting a slowing down of monogalactosyl diacylglycerol biosynthesis and/or an adaptation to drought stress.

Quantitative Changes of the Lipid and Fatty Acid Composition of Leaves of Aleurites montana as a Consequence of Growth under 700 ppm CO2 in the Atmosphere

Abstract Leaf lipids of Aleurites plants that were cultivated for 5 months in air containing 700 ppm CO2, were compared to those of control plants cultivated at 350 ppm CO2. The content of ether soluble lipids referred to dry matter is the same in CO2-and control plants. The comparison of lipids analyzed as the pigments chlorophyll and carotenoids, phospholipids and glycolipids shows that the ratio of phospholipids and glycolipids is slightly shifted in favor of phospholipids in CO2-plants. Thus, within the group of phospholipids, phosphatidylglycerol and phosphatidylinositol occur in higher concentrations in CO2-plants. Although the differences in the lipid content appear moderate in CO2-and control plants, it is the saturation degree of fatty acids that differs substantially. The fatty acids of CO2-plants contain according to the higher phospholipid content approx. 5% more saturated fatty acids. Stearic acid is three-fold increased. Whereas in the phospholipid fraction saturated fatty acids comprise one half of all fatty acids, the unsaturated fatty acids make up for 80 to 90% in the glycolipid fraction. In CO2-plants not only in the phospholipid fraction but also in the glycolipid fraction saturated fatty acids occur in a higher portion. This means that not only in the cell membrane of CO2-plants but also in the thylakoid membrane the fluidity is decreased. Also in the wax-fraction long-chained carbonic acids with 20 -26 carbon atoms occur. As the portion of these carbonic acids is twice as high in CO2-plants, it is concluded that a stronger formation of the wax layers exists in CO2-plants. By means of Western blotting and by the use of lipid and carotenoid antisera the binding of lipids onto proteins of photosystem II and photosystem I was analyzed. It is seen that besides the major amount of lipids which build up the thylakoid membrane, some lipids are also bound to membrane peptides. Whereas monogalactolipid is bound to the LHCP-complex peptides, to the OEC1 -peptide and the 43 and 47 kDa chlorophyll binding peptides, the anionic lipids sulfoquinovosyldiglyceride and phosphatidylglycerol and digalactolipid are bound to the core peptides of PS II and PS I. β-carotene and the xanthophylls were found to be bound to the core peptides and β-carotene and violaxanthin were also bound to the light-harvesting pigment complex.

Effects of drought-stress on lipids in rape leaves

Abstract One-month-old plants of rape ( Brassica napus cv. Drakkar) were subjected to water-deficit stress by withholding irrigation. Leaf lipid composition from control plants (well-hydrated) and water-stressed plants was analysed. Drought-stress induced a sharp decrease in galactolipid and phospholipid contents, whereas the content of neutral lipids increased. The fatty acid composition of leaf lipids was also affected under water-deficit stress. The percentage of linolenic acid (18:3) decreased mainly in monogalactosyldiacylglycerol and that of linoleic acid (18:2) in phospholipids.

Isolation and characterization of an Arabidopsis mutant deficient in the thylakoid lipid digalactosyl diacylglycerol.

The galactolipids monogalactosyl and digalactosyl diacylglycerol occur in all higher plants and are the predominant lipid components of chloroplast membranes. They are thought to be of major importance to chloroplast morphology and physiology, although direct experimental evidence is still lacking. The enzymes responsible for final assembly of galactolipids are associated with the envelope membranes of plastids, and their biochemical analysis has been notoriously difficult. Therefore, we have chosen a genetic approach to study the biosynthesis and function of galactolipids in higher plants. We isolated a mutant of Arabidopsis that is deficient in digalactosyl diacylglycerol by directly screening a mutagenized M2 population for individuals with altered leaf lipid composition. This mutant carries a recessive nuclear mutation at a single locus designated dgd1. Backcrossed mutants show stunted growth, pale green leaf color, reduced photosynthetic capability, and altered thylakoid membrane ultrastructure.

Effect of lead ions on lipids and antioxidant complex activity of Capsicum annuum L leaves, pericarp and seeds

AbstractThe composition of the main lipid classes in leaves, pericarp and seeds of pepper (Capsicum annuum L), and the effect of seedlings immersion in lead and sodium acetate nutrient solutions were investigated. Lead ions accumulated mainly in leaves; in pericarp and seeds the concentration of lead was more than 10 times lower. The influence of lead ions on the leaf lipid composition was expressed most in the last stages of plant development. Treatment with lead acetate caused a decrease in the activity of the antioxidative complex in pepper seeds.

A Mutant of Arabidopsis with Increased Levels of Stearic Acid

A mutation at the fab2 locus of Arabidopsis caused increased levels of stearate in leaves. The increase in leaf stearate in fab2 varied developmentally, and the largest increase occurred in young leaves, where stearate accounted for almost 20% of total leaf fatty acids. The fatty acid composition of leaf lipids isolated from the fab2 mutant showed increased stearate in all the major glycerolipids of both the chloroplast and extrachloroplast membranes. Although the stearate content was increased, the fab2 mutant still contained abundant amounts of 18:1, 18:2, and 18:3 fatty acids. These results are consistent with the expectations for a mutation partially affecting the action of the stromal stearoyl-acyl carrier protein desaturase. Positional analysis indicated that the extra 18:0 is excluded with high specificity from the sn-2 position of both chloroplast and extrachloroplast glycerolipids. Although stearate content was increased in all the major leaf membrane lipids, the amount of increase varied considerably among the different lipids, from a high of 25% of fatty acids in phosphatidylcholine to a low of 2.9% of fatty acids in monogalactosyldiacylglycerol.

A Mutant of Arabidopsis Deficient in the Elongation of Palmitic Acid.

The overall fatty acid composition of leaf lipids in a mutant of Arabidopsis thaliana was characterized by an increased level of 16:0 and a concomitant decrease of 18-carbon fatty acids as a consequence of a single recessive nuclear mutation at the fab1 locus. Quantitative analysis of the fatty acid composition of individual lipids established that lipids synthesized by both the prokaryotic and eukaryotic pathways were affected by the mutation. Direct enzyme assays demonstrated that the mutant plants were deficient in the activity of 3-ketoacyl-acyl carrier protein synthase II; therefore, it is inferred that fab1 may encode this enzyme. Labeling experiments with [14C]acetate and lipase positional analysis indicated that the mutation results in a small shift in the partitioning of lipid synthesis between the prokaryotic and eukaryotic pathways. Synthesis of chloroplast lipids by the prokaryotic pathway was increased with a corresponding reduction in the eukaryotic pathway.

Arabidopsis mutants deficient in polyunsaturated fatty acid synthesis. Biochemical and genetic characterization of a plant oleoyl-phosphatidylcholine desaturase.

The overall fatty acid composition of leaf lipids in a mutant of Arabidopsis thaliana was characterized by reduced levels of polyunsaturated 18-carbon fatty acids and an increased proportion of oleate as a consequence of a single recessive nuclear mutation. Quantitative analysis of the fatty acid composition of individual lipids demonstrated that all the major phospholipids of the extrachloroplast membranes are affected by the mutation, whereas the chlorplast lipids show fatty acid compositions only slightly different from those of wild type plants. These results are consistent with the parallel operation of two pathways of lipid synthesis in plant leaf cells (the prokaryotic pathway in the chloroplast and the eukaryotic pathway in the endoplasmic reticulum) and with genetic evidence (Browse, J., Kunst, L., Anderson, S., Hugly, S., and Somerville, C.R. (1989) Plant Physiol 90, 522-529) that an independent 18:1/16:1 desaturase operates on chloroplast membrane lipids. Direct enzyme assays confirmed that the mutant plants are deficient in the activity of a microsomal oleoyl-phosphatidycholine desaturase and demonstrated that this desaturase is the major enzyme responsible for the synthesis of polyunsaturated phospholipids. Despite this deficiency in 18:1-desaturase activity, mutant plants contained relatively high levels of 18:3 in their leaf phospholipids. This finding is interpreted as additional evidence that considerable two-way exchange of lipid occurs between the chloroplast and endoplasmic reticulum and that this exchange allows the chloroplast desaturases to provide lipids containing 18:3 to the extrachloroplast compartment, thus partially alleviating the deficiency in 18:1 desaturase activity.

Effects of EPTC and Dichlormid on Membrane Lipid Composition of Maize Leaves and Roots

Abstract The changes in fatty acid composition of maize leaf lipids caused by EPTC were generally similar to known effects of this herbicide in other plants: decreasing of linolenic acid content and increasing of its precursors, palmitic, stearic, oleic and linoleic acids. However, novel effects were detected in roots where the proportion of minor fatty acid palmitoleic acid was increased from 2.1 to 7.6 and 16.6% by EPTC and EPTC + dichlormid treatments, respective­ly. Simultaneously, the phospholipid content of root lipids was increased by both EPTC as well as EPTC + dichlormid treatments. The possible effects of EPTC and dichlormid on lipid biosynthesis of maize are discussed.

Altered Chloroplast Structure and Function in a Mutant of Arabidopsis Deficient in Plastid Glycerol-3-Phosphate Acyltransferase Activity

Mutants of Arabidopsis thaliana deficient in plastid glycerol-3-phosphate acyltransferase activity have altered chloroplast membrane lipid composition. This caused an increase in the number of regions of appressed membrane per chloroplast and a decrease in the average number of thylakoid membranes in the appressed regions. The net effect was a significant decrease in the ratio of appressed to nonappressed membranes. A comparison of 77 K fluorescence emission spectra of thylakoid membranes from the mutant and wild type indicated that the ultrastructural changes were associated with an altered distribution of excitation energy transfer from antenna chlorophyll to photosystem II and photosystem I in the mutant. The changes in leaf lipid composition did not significantly affect growth or development of the mutant under standard conditions. However, at temperatures above 28 degrees C the mutant grew slightly more rapidly than the wild type, and measurements of temperature-induced fluorescence yield enhancement suggested an increased thermal stability of the photosynthetic apparatus of the mutant. These effects are consistent with other evidence suggesting that membrane lipid composition is an important determinant of chloroplast structure but has relatively minor direct effects on the function of the membrane proteins associated with photosynthetic electron transport.

A Mutant of Arabidopsis Deficient in Desaturation of Palmitic Acid in Leaf Lipids

The overall fatty acid composition of leaf lipids in a mutant of Arabidopsis thaliana was characterized by elevated amounts of palmitic acid and a decreased amount of unsaturated 16-carbon fatty acids as a consequence of a single nuclear mutation. Quantitative analysis of the fatty acid composition of individual lipids suggested that the mutant is deficient in the activity of a chloroplast omega9 fatty acid desaturase which normally introduces a double bond in 16-carbon acyl chains esterified to monogalactosyldiacylglycerol (MGD). The mutant exhibited an increased ratio of 18- to 16-carbon fatty acids in MGD due to a change in the relative contribution of the prokaryotic and eukaryotic pathways of lipid biosynthesis. This appears to be a regulated response to the loss of chloroplast omega9 desaturase and presumably reflects a requirement for polyunsaturated fatty acids for the normal assembly of chloroplast membranes. The reduction in mass of prokaryotic MGD species involved both a reduction in synthesis of MGD by the prokaryotic pathway and increased turnover of MGD molecular species which contain 16:0.

Plant Morphological and Biochemical Responses to Field Water Deficits

The effects of water deficits on leaf glycerolipid composition were analyzed in two photoperiodic strains of field grown cotton (Gossypium kirsutum L.) that differ in sensitivity to drought. Leaves from plants grown under dryland conditions exhibited increased dry weight and specific leaf weight. The average midday leaf water potential in the dryland treatment decreased to -1.9 and -2.4 megapascals, respectively, for the T25 and T185 genotypes. Total leaf lipid content of plants exposed to dryland conditions was 5.9 and 7.5% of leaf dry weight for strain T25 and T185, respectively. The difference in leaf lipid content between these genotypes was caused by water deficits and was attributed to loss of both phospholipids and glycolipids in strain T25. There was no apparent loss of phospholipids due to water deficits in the T185 genotype; however, a significant loss of glycolipids was partially compensated by a 2-fold increase in triacylglycerol. No change in triacylglycerol was found between treatments in T25 leaves. Water deficit caused a significant decline in the relative degree of acylunsaturation in phospholipids and glycolipids from both genotypes; however, the double bond index for triacylglycerol increased in both genotypes. It is believed that the observed responses of leaf lipid composition to dryland conditions may be an additional criterion for characterization and selection of new drought-tolerant cotton genotypes.

Fatty acid composition of leaf lipids determined after combined digestion and fatty acid methyl ester formation from fresh tissue

A procedure which uses hot methanolic HCl to digest fresh tissue and simultaneously convert the fatty acids of the leaf lipids to the corresponding methyl esters is described. Extraction of the fatty acid methyl esters into a small volume (0.3 ml) of hexane means that a sample for GLC analysis can be taken directly from the tube used for the digestion/methylation reaction. The procedure provides a fatty acid analysis which is comparable to that obtained by a more conventional technique involving separate extraction, saponification, and methylation steps, but the overall yield is reduced by 10-20%. The analysis can be made quantitative by including an internal standard with the tissue sample.

A VIRESCENS MUTANT OF PHASEOLUS VULGARIS: PHOTOSYNTHESIS AND METABOLIC CHANGES DURING LEAF DEVELOPMENT

SummaryFixation of 14CO2, photophosphorylation, and protein, lipid and RNA composition have been compared for primary and trifoliate leaves of various ages of control and mutant plants.Except when old, leaves of control plants fix more CO2 than do those of the mutant, but the carboxylation pathways seem similar in the two plants. The level of Fraction I protein and that of ribulose diphosphate carboxylase activity are also similar, but lower in leaves of the mutant. Photophosphorylation per chloroplast mediated by photosystems I and II, tends to be slightly higher in the mutant, despite lower levels of chlorophyll in mutant plastids. Small differences in amount and composition of leaf lipids, but large differences in RNA content were found. Mutant leaves show a higher initial content of cytoplasmic ribosomal RNA than do controls; as leaves age this position is reversed. Chloroplast ribosomal RNA is initially similar, but continued synthesis is greater and more prolonged in the mutant.The significance of these data is discussed in relation to the nature of the mutation.