Ultrastructure and lipid composition of etioplasts in developing dark-grown wheat leaves

Changes in the ultrastructure and lipid composition of etioplasts have been evaluated in three regions from the base to the tip of 8-day-old darkgrown wheat leaves and in the upper-2/3 region of etiolated leaves of different ages. In developing darkgrown tissues, the main morphological changes that etioplasts undergo consist of an increase in the amount of thylakoïds which, in the most mature etioplasts, align in parallel arrays. Concomitantly, galactolipids and sulfolipid form an increasing proportion of the total lipids. Trans-3-hexadecenoic acid was not detectable in phosphatidylglycerol (PG) of etioplasts showing appressed thylakoïds isolated from 5-day-old leaves, but was present in significant amounts in etioplasts in the basal part of 8-day-ols leaves in which membrane appression was barely visible. The proportions of this acid increase as etioplasts develop, reaching 25% of the PG fatty acids (1.2% of the total fatty acids) in the most differentiated etioplasts. In wheat etioplasts, it appears that trans-3-hexadecenoic acid may accumulate in considerable amounts in darkgrown tissues and that its accumulation is not directly involved in membrane appression.Abbreviations AP phosphatidic acid - DGDG digalactosyldiacylglycerol - MGDG monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - PG phosphatidylglycerol - PI phosphatidylinositol - PS phosphatidylserine - SL sulfolipid     

Tissue localization of phytochrome in dark-grown barley leaves

Phytochrome was spectrophotometrically determined to be differentially concentrated among separated tissues of dark-grown, norflurazon-treated barley l     

Lipid metabolism in ageing leaves of dark-grown barley seedlings

The rapid senescence of the etiolated leaves of dark-grown barley seedlings in the dark is accompanied by the loss of those lipids associated with the plastids. The linolenate content of the plastid glycerolipids rapidly decreased whereas it tended to increase in the extraplastidic phospholipids. Kinetin treatment slowed down the loss of the plastid lipids and their constituent fatty acids. The hormone treatment brought about increased linolenate, particularly in phosphatidylcholine and monogalactosyldiacylglycerol. The senescing leaf attempts to adapt to ageing by increased membrane synthesis and/or membrane repair. Kinetin appears to control the sequential desaturation of oleate to linolenate.     

The association of protein synthesis with protochlorophyllide holochrome regeneration in dark-grown barley leaves

A light-stimulated increase in incorporation of radioactive amino acids into protein associated with protochlorophyllide holochrome occurs concomitantly with the regeneration of phototransformable protochlorophyllide in dark-grown barley leaves. This increase in radioactivity and the protochlorophyllide regeneration process are both abolished by incubation of the leaves with inhibitors of cytoplasmic protein synthesis. Prelimiary data implicate protein in the molecular weight range of 45,000–60,000 daltons in this process.     

Iron-deficiency in pea leaves: Effect on lipid composition and synthesis

The lipid composition of chlorotic leaves of Pisum sativum L. cv. Kelvedon Wonder, developed under iron-deficiency was determined and compared to similar material developed under normal nutrient conditions. All lipid classes were affected by iron-deficiency but to different extents, and thylakoid lipids were more affected than non-thylakoid lipids. The most striking results concerned changes in the fatty acid content of the main polar lipids. The linolenic acid of the galactolipids decreased to the benefit of more saturated fatty acids, mainly linoleic acid. In phosphatidylglycerol, the proportion of Δ³- trans -hexadecenoic acid decreased. Using radioactive acetate, lipid synthesis was investigated. Desaturation leading to linoleic acid was less affected by iron-deficiency than desaturation leading to Δ³- trans -hexadecenoic and linolenic acids.     

Specific leaf area in barley: individual leaves versus whole plants

We have explored the relationships between specific leaf area calculated for a whole plant and its individual leaves. Barley was grown in hydroponics in controlled environment cabinets. Plants were harvested on the basis of physiological age (defined as the number of days after full expansion of leaves on the main stem) and the area and weight of whole, fully expanded, leaves measured and specific leaf area (SLA) of individual leaves or whole plants calculated. Specific leaf area calculated for individual leaves (SLA_L) varied with leaf position and with leaf age after full expansion whereas SLA calculated for whole plants (SLA_P) varied with plant age. The same conclusions were reached whether the results were based on total dry weight or dry weight minus soluble carbohydrates ('structural weight'). Transferring plants to shade on the day of full expansion of the third leaf on the main stem increased the SLA_P, and also SLA_L of leaves 3 and 4 on the main stem (leaf 4 being the younger leaf of the two), because of a decrease in the 'structural weight' of these leaves. However SLA_L of leaf 2 (which was older than leaf 3) was not affected by shading; the effect was confined to leaves developing in the new conditions.     

Light-induced changes in the lipid composition and ultrastructure of plastids from potato tubers

Sandelius, A. S. and Liljenberg, C. 1982. Light-induced changes in the lipid composition and ultrastructure of plastids from potato tubers. – Physiol. Plant. 56: 266–272.
Amyloplasts and starch containing plastids from green tissue – amylochloroplasts – from potato tubers ( Solanum tuberosum L., var. King Edward) were separated from other cell organelles by sedimentation in a discontinuous sucrose gradient. Their lipid composition was analysed with emphasis on galactolipids and phospholipids and the fatty acid compositions of these lipids. Irradiation of the tubers caused increased ratios of monogalactosyl diacylglycerol to digalactosyl diacylglycerol and of total galactolipids to total phospholipids in the plastid membranes. Furthermore, the degree of unsaturation of the fatty acids increased in all lipid classes analysed, this effect being most prominent in the galactolipids. The ultrastructural studies made on tuber tissue revealed that irradiation caused a change in starch grain size distribution concomitant with formation of membrane structures resembling grana within the envelope. In many cases prolamellar bodies and plastoglobuli were present.     

The ultrastructural development of plastids in leaves of maize plants exposed to continuous illumination

Summary Chloroplast differentiation in relation to increasing leaf age has been investigated in maize plants exposed to continuous illumination. In the young leaves the proplastids differentiate into chloroplasts containing well organized grana as well as prolamellar bodies. In the older leaves, while plastids differentiate, the prolamellar bodies are no longer detectable. Chloroplast ability to build up prolamellar bodies does not seems so much a light dependent process as it is affected by cell differentiation rate.Supported by a grant of C.N.R.     

The presence of phytochrome in purified barley etioplasts and its in vitro regulation of biologically-active gibberellin levels in etioplasts

Data are presented confirming that purified barley etioplasts contain, or have associated with them, consistently detectable amounts of photoreversible phytochrome. Etioplasts, separated from mitochondrial contamination by sucrose gradient centrifugation, respond in vitro to red light treatment by an increase in the level of extractable gibberellin-like substances. It is concluded that earlier reports of the substances. It is concluded that earlier reports of the phytochrome regulation of biologically-active gibberellin levels in crude plastid fractions represent responses of the etioplast alone.     

The effects of lead and kinetin on greening barley leaves

The content of lead in greening etiolated barley leaves remained the same, regardless the time of incubation of excised leaves in the presence of lead ions (8–24 h). The lead deposits have not been detected within mesophyll cells, but were found in intercellular spaces of mesophyll, in guard cells and in cuticle covering stomata. This suggests that lead may be transported in the leavesvia transpiration stream. Lead reduced the content of chlorophyll, especially chlorophyllb content and the average number of grana, whereas in the presence of kinetin the content of chlorophyll increased. In the combined treatment (lead + kinetin) kinetin diminished the inhibitory effect of lead on the chlorophyll content. The number of chloroplasts in mesophyll cells remained unchanged after lead treatment, whereas kinetin alone or applied together with lead increased the average chloroplasts number. The thylakoids system in chloroplasts of kinetin and kinetin + lead treated plants was similar to that observed in control, although the grana number was smaller. Both lead and kinetin increased the content of condensed chromatin in nuclei.     

Air ion effects on RNAse activity in green barley leaves

Previously we reported that green barley leaves floated on the surface of a solution of EDTA and exposed to light undergo severe chlorosis. Such bleaching was substantially reduced by (+) or (–) small air ions. EDTA bleached leaves contained more RNA than did the controls. In the present work we found that (+) and (–) air ions markedly increased the RNAse activity of leaves floated on water in the presence or absence of light. EDTA in solution diminished RNAse activity and air ions do not affect this process. In the light there was a loss of RNAse protein; air ions do not influence the reaction. Even larger decreases in RNAse protein develop if EDTA is added to the water and here again air ions were without effect. RNA fractionation of leaves prior to exposure to water or light yielded a typical curve with four peaks representing: RNA, RNA-DNA, Ribosomal-DNA and Messenger-RNA. After 24 hours in water and light the peaks were much lower and were shifted to the right. Air ions did not effect the alternation in profiles. After 12 hours EDTA solution in the light produced 14 peaks instead of four. This profile disruption was eliminated by treatment with (+) or (–) air ions.

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Zusammenfassung Wir haben früher berichtet, dass grüne Gerstenblätter, die auf der Oberfläche einer EDTA-Lösung treiben, bei Belichtung eine schwere Chlorose aufweisen. Dieser Bleichungseffekt ist in Anwesenheit von (+) und (–) kleinen Luftionen erheblich vermindert. EDTA gebleichte Blätter enthalten mehr RNA als Kontrollen. Wir fanden in dieser Arbeit, dass (+) und (–) Luftionen die RNAse-Aktivität treibender Blätter auf Wasser mit und ohne Belichtung stark erhöhen. EDTA-Lösung verminderte die RNAse-Aktivität und darauf hatten Luftionen keinen Einfluss. Bei Lichtexponierung fiel der Anteil an RNAse-Protein; Luftionen beeinflussten diese Reaktion nicht. Der RNAse-Proteinanteil fiel weiter ab, wenn EDTA zugegeben wurde; auch darauf hatten Luftionen keinen Einfluss. Die RNA-Fraktionierung der Blätter vor dem Exponieren auf Wasser und im Licht ergab eine typische Kurve mit 4 Gipfeln (RNA, RNA — DNA, Ribosomen-DNA und Messenger-RNA). Nach 24 Stunden im Wasser und Licht waren die Gipfel flacher und rechtsverschoben, unabhängig von der Einwirkung von Luftionen. EDTA-Lösung und Licht bewirkten nach 12 Stunden 14 Gipfel anstatt 4. Diese Auflösung des Profils wurde durch Einwirkung von (+) und (–) Luftionen unterbunden.

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Resume On a rapporté dans un précédent mémoire que les feuilles vertes d'orge flottant à la surface d'une solution aqueuse de EDTA présentent des symptômes importants de chlorose dès qu'elles sont exposées à la lumière. Ces symptômes sont nettement moindres lorsqu'on introduit de petits ions (+) ou (–) dans l'air ambiant. Les feuilles chlorosées par EDTA contiennent plus de RNA que les feuilles de contrôle. Dans le présent travail, on démontre que les ions (+) et (–) de l'air augmentent de façon marquée la réduction du RNA dans les feuilles flottant sur l'eau et cela avec ou sans lumière. Une solution de EDTA diminue le phénomène et l'ionisation de l'air est sans effet. Par suite de l'exposition à la lumière, la proportion de la proteine issue de la dite réduction diminue et la présence d'ions dans l'air est sans effet. La proportion de la dite proteine diminue encore si l'on ajoute du EDTA et l'ionisation n'a également pas de répercussions sur ce phénomène. Lors de la distillation fractionnée du RNA tiré des feuilles avant leur traitement par l'eau et la lumière, on obtient une courbe typique avec 4 maximums correspondant à RNA, RNA-DNA, DNA ribosomal et RNA Messenger. Après 24 heures de traitement à l'eau et à la lumière, les pointes sont moins prononcées et déplacées vers la droite et cela quelle que soit l'ionisation de l'air. Un traitement de 12 heures à la solution de EDTA et à la lumière a eu pour effet de produire 14 maximums le long de la courbe au lieu de 4. Cette modification de la courbe a été supprimée par une ionisation positive ou négative de l'air ambiant.

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This work was supported by: (1) a grant (5 RO 1 AP00002-12) from the Air Pollution Control Office, Environmental Protection Agency, Department of Health, Education and Welfare and (2) the Bureau of Medicine and Surgery of the United States Navy.     

Air ion effects on EDTA-induced bleaching in green barley leaves

If green intact barley leaves are floated on the surface of a solution of EDTA (0.05 M, pH 7.0) and exposed to light, a severe chlorosis or bleaching is observed in the leaf tissues. This EDTA-bleaching effect can be quantitated in terms of the tissue content of chlorophylls a and b.The EDTA-bleaching effect is weakened by exposing to either negative or positive air ions. The addition of casein hydrolysate (2%) also protects intact green leaves against EDTA-bleaching.This protective effect of casein hydrolysate is significantly augmented by either negative or positive air ions. The leaf tissue content of protochlorophyll is not uniformly affected by EDTA or air ions.A hypothetical mechanism involved in the phenomena described has been proposed.

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Zusammenfassung Wenn heile grüne Gerstenblätter, die auf der Oberfläche einer Lösung von EDTA (0,05 M, pH 7,0) treiben, Licht ausgesetzt werden, tritt eine starke Chlorose oder Bleichung des Blattgewebes ein. Dieser EDTA-Bleichungseffekt kann quantitativ über den Gehalt an Chlorophyll a und b im Gewebe erfasst werden.Bei Einwirkung von positiven und negativen Luftionen wird der EDTA-Bleichungseffekt abgeschwächt. Die Zugabe von Caseinhydrolysat (2%) schützt heile grüne Blätter vor der Bleichung. Dieser Schutzeffekt des Caseinhydrolysats wird signifikant sowohl durch negative als auch durch positive Luftionen verstärkt.Der Anteil an Protochlorophyll im Blattgewebe wird durch EDTA und Luftionen nicht einheitlich beeinflusst.Eine Hypothese zur Erklärung dieser Phänomene wird vorgelegt.

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Resume Si l'on place des feuilles d'orge saines et vertes à la surface d'EDTA (0,05 M, pH 7,0) et qu'on les expose à la lumière,on constate alors une forte chlorose ou décoloration du tissus foliaire. Cet effet décolorant du EDTA peut être déterminé quantitativement par la teneur en chlorophylle a et b du tissus.La présence d'ions positifs ou négatifs dans l'air diminue les effets décolorants d'EDTA. L'adjonction d'hydrolyse de caséïne (2%) protège les feuilles vertes et saines de la décoloration. Cet effet protecteur est renforcé de façon significative par des ions de l'air aussi bien positifs que négatifs.La teneur de protochlorophylle dans les tissus végétaux n'est pas uniformément influencée par l'EDTA ou l'ionisation de l'air. On présente enfin une hypothèse pour expliquer ces phénomènes.

     

Regulation of delta-aminolaevulinic acid synthesis and protochlorophyllide regeneration in the leaves of dark-grown barley (Hordeum vulgare) seedlings.

Laevulinic acid (Lev) was used to control the rate of protocholorophyllide (PChl) regeneration in the leaves of dark-grown seedlings of barley (Hordeum vulgare) after a brief light treatment. In the leaves given Lev, at concentrations that severely block the resynthesis of protochlorophyllide, there was a massive overproduction of delta-aminolaevulinic acid (AmLev) that was well in excess of that required for the regeneration of PChl observed in the control leaves. Lev, at low concentrations, slightly delayed regeneration and held up, rather than inhibited, the utilization of the AmLev, which accumulated in the tissues. The overproduction and uncontrolled formation of AmLev also occurred in dark-grown leaves treated with a high concentration of Lev and given a light treatment of just sufficient energy to photoreduce only small quantities of the endogenous PChl. Experiments in which a high level of free PChl was induced by incubating the leaves in AmLev indicated that the active species of PChl was that associated with, and bound to, the PChl reductase protein. The results strongly demonstrate a close relationship between the PChl-protein complex and the ability of the leaves to synthesize AmLev.     

The occurrence and photoregulation of flavonoids in barley plastids

Whole-leaf extracts of etiolated or light-grown barley shoots contain the C-glycosylflavones saponarin, lutonarin and lutonarin 3′-methyl ether. Plastids isolated by aqueous techniques contain only saponarin. Contamination experiments using foreign flavonoids indicate that saponarin recovered from plastids is not a contaminant from other cellular fractions. In response to brief red light treatment 24 hr before harvest, saponarin levels are approximately doubled in whole-shoot extracts, but increased about 3.5 fold in plastids. This photocontrolled increase is far-red reversible. Thus saponarin is selectively accumulated in barley plastids and this accumulation is controlled by phytochrome.     

Calcium and phytochrome control of leaf unrolling in dark-grown barley seedlings

The red light-stimulated component of unrolling in sections from 7-d-old dark-grown barley (Hordeum vulgare L.) leaves is inhibited by ethyleneglycol-bis-(-aminoethyl ether)-N,N,N,N-tetracetic acid (EGTA). A free-Ca²⁺ activity of less than 40 M restores the ability to respond to red light, but only if supplied within 1 h of red light. Magnesium ions are an ineffective substitute. At least two processes in unrolling appear to be Ca²⁺-sensitive.Fluence-response measurements indicate that the levels of the far-red-absorbing from of phytochrome (Pfr) still present 4 h after red-light treatment should be above saturation for the unrolling response; consequently, loss of Pfr does not explain the loss in effectiveness of Ca²⁺ during prolonged EGTA treatment. However, if a further red-light treatment is given simultaneously with Ca²⁺ addition 4 h after the initial light stimulus, then full unrolling occurs in EGTA-treated sections. These data indicate that, under normal circumstances, a functional change in the properties of Pfr must occur, uncoupling it from the transduction chain.Abbreviations EGTA ethyleneglycol-bis-(-aminoethylether)-N,N,N,N,-tetracetic acid - FR far-red light - Mes 2-(N-morpholino)ethanesulphonic, acid - Pfr far-red absorbing form of phytochrome - Pr red-absorbing form of phytochrome - R red light     

Effects of light and temperature on the composition of epicuticular wax of barley leaves

The amount of wax/cm² on expanding primary leaves of Bonus barley depends on both the photo- and thermoperiods in which the seedlings are grown. With a temperature cycle of 15–10°, transfer of dark grown leaves to the light stopped leaf expansion and after 24 hr yielded 2·5 times more wax/cm² than is characteristic for light grown leaves. This demonstrates that wax synthesis and extrusion is not directly correlated with leaf expansion. The relative amounts of the wax classes formed by the decarboxylation pathways (< 1%), the reductive pathways (89%) or only by elongation (10%) are the same in light and dark. Within the reductive pathways, however, light stimulates aldehyde formation. Both environmental parameters can strongly influence the chain length composition of the wax classes. In the light one chain length or one group of chain lengths dominates a given wax class. In the dark two prominent chain lengths or groups thereof are found. The major chain length in these two groups differs by two or more carbons.