Changes In Chloroplast Ultrastructure Research Articles

Changes in Chloroplast Ultrastructure during the Senescence of Leaves in Rice Plants

The flag leaves were sampled from rice plants of the paddy field at intervals of 10 days after the full expansion, and ultrastructure of the chloroplasts was observed by electron microscope. When the leaves had just fully expanded, the large starch grains accumulated in the chloroplasts, but afterwards the starch grains gradually decreased and after 30 days they almost disappeared (Figs. 1, 5, 6 and 7). The number of thylakoids per granum continued to increase for 10 days after leaf expansion (Fig. 3). The separation of thylakoid membranes, which is the first sign of destruction, was observed in some chloroplasts at 20 days after leaf expansion (Fig. 6). The size of chloroplasts and the number of grana continued to increase for 30 days after leaf expansion (Figs. 1 and 2), but they were followed by the breakdown of inner membrane system and by the decrease in amount of stroma (Figs. 7 and 8). As the inner membranes breakdown, the leaf colour changed to yellow-green and the plastoglobuli increased in size and number (Fig. 4). At the ripening stage of rice plants, ultrastructure was compared among chloroplasts in the upper five leaves (Table 1). Structural differences were not so marked among chloroplasts in the upper three leaves. However, the chloroplasts in the fourth leaf counted downwards from the flag leaf, showed a disappearance of the starch grains, a decrease in number of the grana, and a spectacular accumulation of the plastoglobuli. In the yellow area of the fifth leaf, the chloroplasts shrank because of the disappearance of grana and stroma (Fig. 9), and finally the chloroplasts envelope disappeared (Fig. 10). The similar pattern of destruction as mentioned above was observed in the chloroplasts from seedling leaves, but the destruction was more rapid than those at the ripening stage.

Effects of Gibberellin and Several Growth Retardants on Plastid Ultrastructure in the Hepatic Marchantia polymorpha

Effects of Gibberellin and Several Growth Retardants on Plastid Ultrastructure in the Hepatic Marchantia polymorpha

BIOCHEMICAL AND PHYSIOLOGICAL ASPECTS OF LEAF DEVELOPMENT IN COCOA (THEOBROMA CACAO)

SUMMARYA quantitative study of the changes in chloroplast ultrastructure and carotenoids was made during cocoa flush leaf development. Plastid length, breadth, number of grana per plastid, index of lamellae per plastid and the number of lamellae per granum all increased with chlorophyll content. The number of chloroplasts per cell remained constant at three throughout leaf development. Lutein, neoxanthin, violaxanthin, α‐carotene and †‐carotene were the only carotenoids found in measureable amounts in cocoa leaves, and they all developed in parallel with chlorophyll. The phase of maximum chloroplast development in cocoa does not occur until after the termination of leaf expansion.

Ultrastructural changes in chloroplasts of Populus tremula L., leaves affected by the fungus Melampsora pinitorqua Braun. Rostr

Infection of aspen leaves by the rust Melampsora pinitorqua causes ultrastructural changes in the chloroplasts. These are generally similar to the changes observed in chloroplasts of other plants infected with rusts or viruses, treated with various chemicals or during the process of leaf senescence. It appears that one of the mechanisms by which the rust may attack the leaf tissues of aspen is by exudation of enzymes involved in the degradation of starch and synthesis of glycogen.

Ultrastructural changes in chloroplasts resulting from fluctuations in NaCl concentration: freeze-fracture of thylakoid membranes in Dunaliella salina.

The structure of chloroplasts isolated from Dunaliella salina has been studied with respect to changing concentrations of sodium chloride in the culture medium. Freeze-fracture replicas and thin sections of intact chloroplasts do not exhibit any noticeable changes in structure at concentrations ranging between 3.5 and 25% NaCl. Chloroplasts isolated from algal cells that have been acclimatized to the higher salt concentration show a change in the thylakoid membranes. The thylakoid membranes appear compressed over a major portion of the membrane surface, with only the end of the thylakoid membranes unappressed. The number of particles per unit area on the B face is also altered by the salt concentration. The chloroplasts acclimatized to 25% NaCl have about 3 times the number of particles per unit area on a B face of end-membranes as on a comparable face of thylakoid membranes acclimatized to low (3.5% NaCl) salt concentration. These morphological changes can be reversed if the chloroplasts acclimatized to high or low salt concentrations are returned to a medium of different salt concentration prior to freeze-fracturing.

Chloroplast ultrastructure and ethylene production of senescing and rust-infected cowpea leaves

An investigation of the changes in chloroplast ultrastructure induced by rust infection of cowpea leaves revealed that although initial changes in the pustule center resembled those observed in naturally senescing leaves, subsequent changes more closely resembled chromoplast development in certain ripening fruit. Ethylene treatment of healthy leaves induced changes similar to those seen during the later stages of pathogenesis and detached infected leaves released greater amounts of this gas than controls. The restriction of the chromoplast-like changes to the pustule center and the fact that the endogenous ethylene levels of newly picked infected leaves were barely higher than those of comparable healthy tissue suggested that most of the increased production of this gas was associated with the relatively small region of high fungal concentration. In contrast, naturally senescing leaves contained one-sixth, or less, of the ethylene content of infected leaves and released about half as much as infected tissue when detached. Thus it is suggested that, in many plants, increased ethylene production results in chromoplast-like development of the chloroplasts and that the degree of such development during pathogenesis or senescence may reflect the degree of ethylene production during these processes.

Lead-induced ultrastructural changes in chloroplasts of the hydrophyte, Ceratophyllum demersum

Summary Striking changes in chloroplast fine structure accompany the growth of Ceratophyllum demersum in an aquatic medium containing lead nitrate chelated with EDTA. A change in the organization of the lamellar system is the most noticeable feature. While chloroplasts of untreated leaf cells contain many well-developed grana, those of lead-exposed leaf cells show a reduced number of grana stacks and a highly congested fretwork. The amount of stroma in relation to the lamellar system is markedly reduced, leaving little unoccupied matrix within the organelle. Other observable changes involve the starch grains and the conspicuous plastoglobuli. The former are either absent or greatly reduced in size. The plastoglobuli, in marked contrast to those present in untreated chloroplasts, exhibit a total loss of electron density. Additionally, they often appear to be smaller in size and greater in number than in chloroplasts of untreated plants. It is suggested that since these morphological alterations within the organelle may be sufficient to eventually result in cell death, the chloroplast should be considered as the primary candidate for lead-associated phytotoxicity. Possible relationships between sites of inhibition and the resultant structural abnormalities are discussed.

Some effects of systemic infection by tomato spotted wilt virus on chloroplasts of Nicotiana tabacum leaves

Ultrastructural changes in chloroplasts of tobacco leaves infected by tomato spotted wilt virus were examined by electron microscopy. Peripheral vesicles were observed in chloroplasts of infected tissue at the time of appearance of systemic vein-clearing and these vesicles increased in number and extent with development of infection. The vesicles resembled the chloroplast peripheral reticulum found in plants that fix carbon into C 4 dicarboxylic acids, but the activity of phosphoenolpyruvate carboxylase (the enzyme responsible for carbon fixation in C 4 plants) decreased in infected tissue at later stages of infection. Inhibition of virus synthesis by cycloheximide, but not chloramphenicol, indicated that cytoplasmic ribosomes but not chloroplast ribosomes were involved in virus multiplication.

On the distribution and development of lattice bodies in apothecial cells of the fungus Ascobolus

Lattice bodies, symmetrical membranous aggregates occurring naturally in apothecial cells of Ascobolus stercorarius, are examined as to distribution in the various cell types comprising the ascocarp and as to their spatial arrangement with respect to other subcellular structures present. Their direct development from an amorphous lipoprotein matrix is delineated, and comparisons are drawn from recent literature on ultrastructural changes in chloroplasts during development and dedifferentiation. The presence of similar ordered membranous structures in representative organisms of higher plants, animals, and prokaryotes is comprehensively reviewed, and possible lattice body functions are considered with reference to the occurrence of complex membrane aggregates in certain specialized cells of other organisms.

Ultrastructural changes of chloroplasts in detached parsley leaves yellowing in darkness and the influence of kinetin on that process

Detached parsley leaves kept in darkness became yellow and lost their turgor. The most visible symptoms of the chloroplast degeneration were: a shrinkage of the chloroplast volume, the accumulation of osmiophilic masses on their surface, the breakdown of the stroma thylakoids, the disorganization of grana, an increase in the number and volume of plastoglobuli and, at last, the degradation of the entire plastid. Kinetin inhibits the yellowing process of parsley leaves and the degeneration of plastids. Experiments to reverse this process failed.

Effects of Salt Treatments of Cotton Plants (Gossypium hirsutum L.) on Leaf Mesophyll Cell Microstructure

AbstractCotton plants (Gosspium hirsutum L.) were grown hydroponically in a controlled environment to study the effect of three salt treatments on the microstructure of leaf mesophyll cells. Sodium chloride was added to a basic nutrient solution in amounts to give low‐, medium‐, and high‐salt treatments.Leaves of the same chronological age from the fifth true node were used for electron microscopic studies of mesophyll cell microstructure. Electronmicrographs showed many crystalline deposits in leaf mesophyll cells for the low‐ and high‐salt treatments, but not for the medium‐ salt treatment. Heavy deposits of these crystals occurred in the cytoplasm, central vacuole, cell walls, and intercellular spaces. The high‐salt treatment also produced many necrotic mesophyll cells and changes in chloroplast ultrastructure, and more mitochondria than cells from the medium‐ and low‐salt treated leaves.

Light-Induced Effects of Tris on the Ultrastructure of Leaf Tissue

The effects on ultrastructure of tris(hydroxymethyl)aminomethane (Tris), pH 8� 0, were examined in leaf segments of wheat, barley, and maize in both light and dark. Tria in the light induces drastic changes in chloroplast ultrastructure which are not apparent in the dark except in mesophyll cells of maize. Both grana and stroma lamellae are affected and structural changes are apparent after treat-mentwith Tris for 3 hr. Vacuoles appear in the chloroplasts and both grana and stroma lamellae frequently Wldergo coiling. At later stages, disruption of the tonoplast occurs. The action of Tris appears to be specific for chloroplast membranes and the tonoplast, there being no apparent effect on the plasmalemma, or the membranes of mitochondria or microbodies.

Ultrastructural Changes of Tobacco Chloroplasts Induced by Pyriclor

Treatment of tobacco (Nicotiana tabacumL., var. NC-402) with 2,3,5-trichloro-4-pyridinol (pyriclor) leads to progressive disruption of chloroplast ultrastructure. Initial changes include the inception of a spherical form, swelling of the fret system, and commencement of loss of starch. More advanced changes include the complete disappearance of starch, further swelling and disorganization of the fret membrane system, followed by swelling and disruption of the membranes of the granal discs and rupture of the chloroplast envelope. The changes induced by pyriclor on chloroplast ultrastructure in tobacco are analagous to those caused by 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) on kidney bean (Phaseolus vulgarisL.) and barnyardgrass (Echinochloa crusgalliL. Beauv.). The shape and size of mitochondria were not altered by treatment with the chemical; however, there appeared to be a significant increase in the number of mitochondria present when alterations in chloroplast structure could be seen. The appearance of visual symptoms of phytotoxicity (chlorosis) correlated with the onset of disruptive changes in chloroplast ultrastructure.

Ultrastructural changes in chloroplasts and cytoplasm caused by local infection of tobacco with tobacco mosaic virus and cucumber virus 4

Abnormal formations were observed in ergastoplasm and chloroplasts of leaf cells of tobacco, Nicotiana tabacum L. var. Xanthi-nc, locally infected with tobacco mosaic virus (TMV) and cucumber virus 4 (CV4) ; such changes could be detected neither in healthy cells nor in cells of other hosts infected with these viruses systemically. Chlorotic lesions were obtained by mechanical inoculation of mature leaves and incubation in artificial light at a constant temperature of 30°C. Abnormal formations (vesicular bodies) originated probably by invagination of the membrane limiting a chloroplast. The same bodies were found in the cytoplasm, but their origin was not observed. The bodies contained particles similar to ribosomes in size, but rhombic in shape. Later these particles coalesced in larger osmiophilic granules that joined in a uniform osmiophilic matter filling up the whole body. Neither rod-like particles nor crystalline inclusions (being common in systemically infected cells) were found in specimens made from locally infected leaf tissues.Some differences were observed between TMV and CV4 local infections: that caused by TMV was characterized by fine granulated structure of the stroma; that caused by CV4, by a vesicular and granulated structure.