Glycolipid Degradation in Leaves of the Thermophilic Cucumis sativus as Affected by Light and Low‐Temperature Treatment

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In frost‐hardened spinach leaves (Spinucea oleracea L. ev. Vroeg Reuzenblad) an enhanced content of water‐soluble non‐protein sulfhydryl compounds was observed. The enhancement was due to higher levels of glutathione as well as to other non‐protein‐bound sulfhydryl compounds. In addition glutathione reductase activity was increased upon hardening. The affinity of the enzyme for oxidized glutathione was slightly lowered during hardening. The significance of glutathione accumulation during frost‐hardening is discussed. Exposure of spinach to NaCl‐stress did not affect the levels of glutathione and glutathione reductase of the leaves. In addition the kinetic properties of the enzyme remained unaltered by salinity. It is suggested that glutathione and glutathione reductase activity are not involved in adaptation of spinach to saline conditions.

Section: Discussionmentioning

confidence: 99%

Effects of frost‐hardening and salinity on glutathione and sulfhydryl levels and on glutathione reductase activity in spinach leaves

Kok

Oosterhuis

1983

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“…Chl a degradation was lower in liposomal dispersions containing Chl a and DPL-PC only. Degradation of linolenic acid was observed in liposomal dispersions containing Chl a + MG 4-DPL-PC as well as in Cucumis discs where a specific breakdown of the linolenoyl chains of the glycolipids was noted (Van Hasselt 1974, De Kok andKuiper 1977).…”

Section: Discussionmentioning

confidence: 99%

“…Extraction of MG from sugar-beet leaves. The extraction of lipids and purification of MG was according to the method described by De Kok and Kuiper (1977).…”

Section: Extraction Of Chl a From Cucumis Leaves Leaves Ofmentioning

confidence: 99%

“…In leaves of Cucumis sativus L. a thermophilic plant, photo-oxidation of the leaf pigments occurs at a temperature slightly above 0°C (Van Hasselt 1972). In addition a breakdown of lipids is observed, especially a decrease in linolenic acid content (Van Hasselt 1974) caused by degradation of the glycolipids (De Kok and Kuiper 1977). Rubin et al (1976) demonstrated photo-oxidation of the (glyco-)lipids in isolated pea chloroplasts after red light induced photo-oxidation of chlorophyll.…”

Section: Introductionmentioning

confidence: 99%

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Photo‐oxidative Degradation of Chlorophyll‐a and Unsaturated Lipids in Liposomal Dispersions at Low‐Temperature

Kok¹,

Hasselt

Kuiper

1978

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Liposomal dispersions in water were used as a tool to study photo‐oxidation of chlorophyll‐a and photo‐oxidation of unsaturated lipids at 1 or 4°C. The presence of monogalactosyl diglyceride stimulated chlorophyll‐a degradation. In addition the level of linolenic acid was decreased in liposomal dispersions containing chlorophyll‐a, dipalmitoyl phosphatidyl choline, and monogalactosyl diglyceride, indicating that monogalactosyl diglyceride and chlorophyll‐a were coupled in the preparations. In liposomal dispersions containing equal (molar) quantities of a‐tocopherol, monogalactosyl diglyceride, and chlorophyll‐a, a‐tocopherol fully protected linolenic acid against photo‐oxidative degradation, while chlorophyll‐a degradation was only slightly reduced. In liposomal preparations containing a‐tocopherol, chlorophyll‐a and phosphatidyl choline, a‐tocopherol catalyzed degradation of chlorophyll‐a. Absorption spectra of the liposomal dispersions showed that the presence of a‐tocopherol caused increased absorption in red light, which was attributed to structural changes in the liposomal preparations and thus could explain the noted effects. Tocopherol itself was rapidly degraded in chlorophyll‐a containing liposomal preparations. Complex formation between chlorophyll‐a and monogalactosyl diglyceride in chloroplasts is suggested and protection by a‐tocopherol against photo‐oxidation in chilling‐sensitive plants; a suggestion which is founded on the similarities that exist between chloroplast preparations and liposomal preparations containing chlorophyll‐a and monogalactosyl diglyceride as regards photo‐oxidative degradation of chlorophyll‐a, a‐tocopherol and linolenic acid.

“…They are interesting because of their adaptability to extreme environments and the presence of specific secondary metabolic products which could be part of the adaptation of lichens, Evernia prttnastri (L,) Ach, is able to withstand high temperatures. Exposure of the lichen to 58°C for 5 h leaves its respiration essentially unaltered (Lange 1953), Eurthermore, Cetraria species are able to maintain 50% of the maximum rate of photosynthesis at -5°C, which clearly is an adaptation to low temperature (Lange 1962), In higher plants adaptation to low temperature and to drought has been related to several parameters as lipid and fatty acid composition of the plants, which may enable the cell membranes to continue to function under adverse conditions, A high degree of unsaturation of the membrane lipids was associated with functioning of plant cells at low temperature (Kuiper 1970, Lyons and Raison 1970, De la Roche et al, 1975, In addition cyclic fatty acids (cyclopropane fatty acids) were indicated to occur in higher plants which are physiologically active in early spring or under drought conditions (Kuiper and Stuiver 1972), In lichens the occurrence of fatty acids common in higher plants has been mentioned only occasionally (Klima 1933, Wagner andFriedrich 1965), More attention has been given to the aliphatic lichen acids, which contain lactone rings or other rings as part of the molecule (Culberson 1969, Asahina andShibata 1971),…”

Section: Introductionmentioning

confidence: 99%

Lipid and Fatty Acid Composition of Tree‐Growing and Terrestrial Lichens

Dertien

Kok

Kuiper

1977

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A comparison of lipid and fatty acid composition was made of the tree‐growing lichens Evernia prunastri (L.) Ach., Parmelia saxatilis (L.) Ach. and Hypogymnia physodes (L.) Ach. and the terrestrial species Cetraria islandica (L.) Ach. and Cladonia impexa Harm. In the terrestrial species the total lipid content varied strongly during spring, while the tree‐growing species showed much less variation. Phospholipid and sterol content of all lichens was unusually low. Monoglycosyl diglyceride was absent from Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, oleic, linoleic and linolenic acid were invariably present in all lichen species. In addition large quantities of extra‐long chain fatty acids like behenic acid, eicosadienoic acid and cyclic aliphatic lichen acids were present in the terrestrial species. The degree of (poly) unsaturation decreased in the order Evernia prunastri, Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, impexa, which decrease was compensated by an increase in extralong chain fatty acids and lichen acids. It is suggested that the lichen acids are of adaptive value for lichen species growing in the terrestrial habitats, which were characterized by extreme diurnal temperature variations. Just as the polyunsaturated fatty acids, lichen acids guarantee at lower temperatures a high flexibility of the membranes involved, at the same time as they are less susceptible to photo‐oxidation at the high daytime temperatures.