Changes In Chloroplast Structure Research Articles

Aging of the photosynthetic apparatus zIV. Similarity between the effects of aging and unsaturated fatty acids on isolated spinach chloroplasts as expressed by volume changes

1. The effects of unsaturated fatty acids have been studied and compared with the known effects of aging on volume changes in isolated spinach chloroplasts. 2. C 18-unsaturated acids, i.e. oleic, linoleic and linolenic acids, and to a lesser extent myristic acid, were the most effective in stimulating swelling and inhibiting light-induced shrinkage. These acids are precisely those which are released in greatest amount from lipids during aging of chloroplast membranes. 3. On the contrary, saturated fatty acids (C 8:0, C 10:0, C 16:0, C 17:0 C 18:0, C 20:0), and also C 22:1, had only slight effects on chloroplast volume changes. 4. Activation of chloroplast swelling and inhibition of light-induced shrinkage by unsaturated fatty acids were found to be time and concentration dependent. Maximum swelling occurred after 20 min with a fatty acid/chlorophyll molar ratio of 9 (200–240 μM per 20 μg chlorophyll/ml) which corresponded to almost full inhibition of light-induced shrinkage. The activity of C 18-fatty acids on swelling could be established in the decreasing order: C 18:1 > C 18:2 > C 18:3 > C 18:0. Although maximum inhibition of light-induced shrinkage was the same after 20 min for the three unsaturated fatty acids, the time required to reach it was inversely related to the number of double bonds. 5. Bovine serum albumin restored light-induced shrinkage inhibited by fatty acids and overcame swelling caused by these compounds. 6. A relationship might exist between the occurrence or the amount of fatty acids in the organelle lipids and their capacity to regulate chloroplast structural changes. Results are compiled in a scheme and discussed as they relate to the known effects of fatty acids and aging on electron flow and energy-linked reactions, on the physicochemical properties and the lipoprotein complexes of the membrane, and on lipid peroxidation.

Chloroplast Structural Changes During Temperature-Induced Bleaching and Re-Greening in a « Golden Leaf » Mutant of Maize

SUMMARYThe modifications of the plastid structures in a Maize mutant, « golden-leaf », have been studied in the electron microscope. In this mutant plastid organization is temperature dependent. At 25°C the chloroplasts are quite regularly structured, but when the corn plants are transferred to 16°C, the plastids become incompletely organized or anomalous. If higher temperature conditions are re-established, the plastids are able to regain their original organization only if a prolamellar body or structured grana, even in an anomalous state, are present. When the plastids are affected by the lower temperature in a very young stage, their modifications become irreversible, and their appearance resembles, also in the regreened tissues, that of albino plastids or of chromoplasts.

Some morphological and physiological effects of palladium on Kentucky bluegrass

Palladium (PdCl2) added to nutrient solution at concentrations greater than 3 mg/l inhibited transpiration of Kentucky bluegrass (Poa protensis L.). In contrast, toxicity only became apparent at 10 mg/l. The effects of palladium included aberrant stomatal histogenesis, inhibition of nodal meristem development, changes in chloroplast structure, and hypertrophy of mesophyll cells, nuclei, and nucleoli. The stomatal aberrations involved accessory cell disorientation which resulted in guard cells not being open to the atmosphere.

The Analysis of Photosynthesis Using Mutant Strains of Algae and Higher Plants

INTRODUCTION Major contributions to the understanding of biological processes have been made with the aid of mutant organisms in which the processes have been disrupted; the use of auxotrophic mutant strains of microorganisms to elucidate metabolic pathways is a classic example of this approach. Muta­ tions that affect chloroplast structure, chlorophyll and carotenoid synthesis, synthesis of components of the photosynthetic electron transport chain, and synthesis of enzymes of the reductive pentose phosphate cycle are known to occur in higher plants and green algae, and it is the purpose of this review to describe how certain mutant strains have been 'used to study the mecha­ nism of photosynthesis. This review will be particularly concerned with the nature and function of components of the photosynthetic electron transport chain as deduced from studies of mutant strains of green algae and higher plants having normal pigment content, and only secondarily will it consider mutant strains having gross abnormalities in either their chloroplast struc­ ture or amounts of pigment. Several excellent general reviews of photosyn­ thesis have appeared recently (1, 2), and the material presented here should be considered as a special supplement to them rather than as an overall view of the subject. In organisms in which genetic analysis is possible, it has been shown that mutations affecting photosynthesis are of both nuclear and extranu­ clear genes. Nuclear gene mutations show a classical Mendelian inheritance, whereas mutations of extranuclear genes usually show maternal inheri­ tance. The plastom mutations of higher plants are examples that show ma­ ternal inheritance, and characteristically these mutations lead to marked changes in chloroplast structure and in the amount of chlorophyll. The principal mutant strains to be considered in this review (Table I) have been obtained from the algae Chlamydomonas reinhardi, Euglena gra­ cilis, and Scenedesmus obliquus and from the higher plants Hordeum vul­ gare, Nicotiana tabacum, and Vida faba. The mutations in C. reinhardi, H.

Ultrastructural and Photometric Evidence for Light-Induced Changes in Chloroplast Structure in vivo

Photometric evidence for a reversible, red-light induced transmission decrease in excised leaf tissue or the thalli of certain marine algae has been obtained under conditions which correspond to the occurrence of a light-induced shrinkage of chloroplasts within the cells. Evidence supporting this conclusion is: A) The kinetics of the nonspecific transmission changes are similar to those observed in chloroplasts in vitro. B) The magnitude of the response is larger than could be accounted for by any known pigment which absorbs at 546 mmu. C) The light-induced transmission changes are optimal at pH 5.5 to 6.5 in the presence of electron flow cofactors and weak acid anions, conditions which are optimal for light-induced chloroplast shrinkage in isolated chloroplasts. D) Examination of chloroplast ultrastructure in dark incubated and illuminated chloroplasts reveals a flattening of the chloroplast structure and shrinkage.

Retention of energy transfer in glycerinated chloroplasts

Chloroplasts (1) and mitochondria (2) undergo structural changes that are coupled to energy-dependent reactions. These changes are closely correlated with conditions of either ATP synthesis or hydrolysis and can be conveniently measured by some physical parameter such as light scattering or absorbancy (3). Furthermore, the addition of ATP plus a divalent cation such as Mg ++ to chloroplasts incubated either in the dark (4) or light results in a rapid shrinkage especially under conditions where ATP hydrolysis has been light triggered (3). These observations led to the hypothesis that some type of contractile protein was involved in these mechanochemical changes. Although Packer and Marchant (3) and Ohnishi (5) have reported the isolation of a protein from chloroplasts which undergoes conformational changes with ATP, the correlation between the system described in chloroplasts and bona fide contractile systems is still uncertain. In this study we extend the correlation between chloroplast structural changes and muscle contraction by the preparation of chloroplast “models” which are analogous to the muscle models of Szent Györgyi (6). This approach was suggested by the recent reports of Nakazawa (7) and Kazakova (8), who have established that mitochondria retain certain responses to ATP following glycerol treatment.

Structural Changes in Phaseolus vulgaris Induced by Atrazine II. Effects on Fine Structure of Chloroplasts

1. The fine structure of the chloroplasts of Phaseolus vulgaris is grossly altered by treatment with atrazine when the plants are kept in the light, but atrazine has no effect in the dark. 2. The following progressive changes in chloroplast structure occur: (a) they become spherical rather than discoid; (b) starch disappears from the lamellar system; (c) the frets or parts of frets are destroyed, leading to the disorganization of the granal arrangement; (d) the compartments of the grana swell; and (e) the envelope and the swollen compartments ultimately disintegrate. 3. It is proposed that these changes are brought about by the formation of a toxic substance or substances involving the interaction of atrazine and light in the presence of chlorophyll. 4. The similarity among these modifications and those caused by other substances or mineral deficiencies and the altered chloroplast structure in lutescens mutants of barley and variegated plants of Humulus are discussed.

THE FINE STRUCTURE OF CHLOROPLASTS FROM MINERAL‐DEFICIENT LEAVES OF PHASEOLUS VULGARIS

Thomson, W. W., and T. E. Weier. (U. California, Davis.) The fine structure of chloroplasts from mineral‐deficient leaves of Phaseolus vulgaris. Amer. Jour. Bot. 49(10): 1047–1055. Illus. 1962.—An electron microscopic study of the changes in chloroplast structure as affected by the stress of nutrient deficiencies is described. Each deficiency produces characteristic changes in the ultrastructure of the chloroplast. In phosphorus and potassium deficiency the plastids develop fully before changes occur; then the grana break down into diffuse, electron‐dense masses, forming a highly ordered lamellar system. The plastids of plants low in nitrogen and magnesium do not reach full development before changes occur. In nitrogen‐deficient plastids, the stroma is greatly diminished and the grana compartments are swollen and reduced in number. In magnesium deficiency, the grana‐fretwork system becomes disorganized and many star‐bodies are formed. The absence of zinc blocks the full development of a grana‐fretwork system, and large vacuoles are formed in conjunction with grana compartments.