Changes In Chloroplast Ultrastructure Research Articles

Chloroplast ultrastructure in leaves of tobacco plants with the introduced gene for the acyl-lipid Δ9-desaturase from Synechococcus vulcanus at normal and low temperature

Ultrastructural changes in chloroplasts of tobacco plants (Nicotiana tabacum L.) with the introduced desC gene for the acyl-lipid Δ9-desaturase from the thermophilic cyanobacterium Synechococcus vulcanus were investigated during plant acclimation to cold. Control plants were transformed with an empty pGA482 binary vector. At optimum growth temperature, a decreased number of grana and thylakoids and an increased number of plastoglobules and their larger area were observed in transgenic plants when compared to control ones. In control plants, acclimation to cold (6 days at 10°C) resulted in the larger areas of chloroplasts and grana. These changes indicated starting cold-induced injuries manifested in swelling of the stroma and a slight decrease in the total number of thylakoids in the chloroplast. In contrast, transgenic plants responded to cold by reducing the chloroplast, granal, and plastoglobule areas. Meantime, the number of thylakoids per granum increased noticeably. The total number of thylakoids in the chloroplast increased from 123 to 203. It was concluded that expression of the acyl-lipid Δ9-desaturase gene in tobacco plants provided for the formation of the cell ultrastructure similar to one characteristic of cold-tolerant plants.

Imaging viral infection: studies on Nicotiana benthamiana plants infected with the pepper mild mottle tobamovirus

We have studied by kinetic Chl-fluorescence imaging (Chl-FI) Nicotiana benthamiana plants infected with the Italian strain of the pepper mild mottle tobamovirus (PMMoV-I). We have mapped leaf photosynthesis at different points of the fluorescence induction curve as well as at different post-infection times. Images of different fluorescence parameters were obtained to investigate which one could discriminate control from infected leaves in the absence of symptoms. The non-photochemical quenching (NPQ) of excess energy in photosystem II (PSII) seems to be the most adequate chlorophyll fluorescence parameter to assess the effect of tobamoviral infection on the chloroplast. Non-symptomatic mature leaves from inoculated plants displayed a very characteristic time-varying NPQ pattern. In addition, a correlation between NPQ amplification and virus localization by tissue-print was found, suggesting that an increase in the local NPQ values is associated with the areas invaded by the pathogen. Changes in chloroplast ultrastructure in non-symptomatic leaf areas showing different NPQ levels were also investigated. A gradient of ultrastructural modifications was observed among the different areas.

Elevated CO2 induces physiological, biochemical and structural changes in leaves of Arabidopsis thaliana

Leaves of Arabidopsis thaliana grown under elevated or ambient CO2 (700 or 370 micromol mol(-1), respectively) were examined for physiological, biochemical and structural changes. Stomatal characters, carbohydrate and mineral nutrient concentrations, leaf ultrastructure and plant hormone content were investigated using atomic absorption spectrophotometry, transmission electron microscopy and enzyme-linked immunosorbent assay (ELISA). Elevated CO2 reduced the stomatal density and stomatal index of leaves, and also reduced stomatal conductance and transpiration rate. Elevated CO2 increased chloroplast number, width and profile area, and starch grain size and number, but reduced the number of grana thylakoid membranes. Under elevated CO2, the concentrations of carbohydrates and plant hormones, with the exception of abscisic acid, increased whereas mineral nutrient concentrations declined. These results suggest that the changes in chloroplast ultrastructure may primarily be a consequence of increased starch accumulation. Accelerated A. thaliana growth and development in elevated CO2 could in part be attributed to increased foliar concentrations of plant hormones. The reductions in mineral nutrient concentrations may be a result of dilution by increased concentrations of carbohydrates and also of decreases in stomatal conductance and transpiration rate.

Ultrastructural changes of chloroplasts caused by tobamovirus infections in different pepper varieties

Ultrastructural changes of chloroplasts caused by tobamovirus infections in different pepper varieties

Differential Sensitivity of Chloroplasts in Mesophyll and Bundle Sheath Cells in Maize, an NADP-Malic Enzyme-Type C4 Plant, to Salinity Stress

The changes in chloroplast ultrastructure and the contents of chlorophyll, Na and K in response to salinity stress were investigated in leaves of maize, an NADP-malic enzyme-type C4 plant species possessing dimorphic chloroplasts. The seedlings were treated with 0, 1, 2 or 3% NaCl for three or five days under a light or dark condition. In both light and dark conditions, the dry weight of salt-treated plants decreased as NaCl concentration increased. Chlorophyll and K contents of the second leaf blade decreased as NaCl concentration increased under the light condition but not under the dark condition. Na content of the second leaf blade was significantly higher at high NaCl concentrations under both light and dark conditions. However, Na content was much lower under the dark condition than light condition. Higher concentrations (2 and 3%) of NaCl significantly increased the size of plastoglobules, decreased the number and size of starch granules and altered the chloroplast ultrastructure. Under the light condition, mesophyll cell (MC) chloroplasts appeared more sensitive to the damaging effect of salinity than the bundle sheath cell (BSC) chloroplasts. MC chloroplasts became more globular in shape and showed swollen and disorganized thylakoids and reduced thickness of grana by salinity. BSC chloroplasts were less affected by salinity than MC chloroplasts. Although chloroplast size and number and size of starch granules were reduced, there was no structural distortion in the thylakoids of BSC chloroplasts. However, the thickness of grana was increased by salinity. Under the dark condition, the chloroplast structure was less affected by salinity. Though the envelope of BSC chloroplasts was occasionally damaged, the thylakoids in both MC and BSC chloroplasts were preserved under salinity stress. The present study suggests that the chloroplast damage caused by salinity is light-dependent and MC chloroplasts are more sensitive to salinity than BSC chloroplasts.

New records of fungal pathogens of euphorbia inarticulata from Aseer region, south-west Saudi Arabia: Neue aufzeichnungen über fungale pathogene von euphorbia inarticulata aus der Aseer-region im südwesten Saudi Arabiens

A 12 month period survey of the fungi associated with Euphorbia inarticulata was evaluated. Sampling was concentrated mainly in Aseer region (South-West Saudi Arabia) and seven fungal species were identified as pathogens of this plant. Melampsora euphorbiae and Alternaria euphorbiicola were the most common species on this plant. Bipolaris euphorbiae, Botrytis ricini, Colletotrichum gloeosporioides, Oidium sp., Sphaceloma poinsettiase and Uromyces euphorbiae were less frequent species. These fungal pathogens were recorded for the first time on Euphorbia inarticulata in Saudi Arabia. Scanning and transmission electron microscopy revealed the colonization of M. euphorbiae, as an example, in leaf tissues of E. inarticulata. Remarkable ultrastructural changes in chloroplasts and nuclei of infected cells of E. inarticulata as a result of infection by M. euphorbiae were observed.

Changes in Chloroplast Ultrastructure in Pssu-ipt Tobacco During Plant Ontogeny

Changes in chloroplast ultrastructure and total content of endogenous cytokinins (CK) were studied during different phases of plant development in transgenic Pssu-ipt tobacco (Nicotiana tabacum L. cv. Petit Havana SR1). Permanent overproduction of CK was found in both rooted (SE) and grafted (G) Pssu-ipt plants in all phases of plant development with the peak in vegetative and flowering phase in the latter ones. No such a correlation was observed in SE on the contrary to control non-transgenic plants (SR1) and grafts (SRG), which showed also CK increase at juvenile and flowering phases. No significant differences in parameters of chloroplast ultrastructure, such as length of chloroplast, starch content, granum width, and number of thylakoids per granum, were proved between chloroplasts from young mature leaves of control and transgenic tobacco during plant ontogeny. Nevertheless, several anomalies in the ultrastructure of cell organelles were found in Pssu-ipt tobacco. Amoeboid shape of chloroplasts was often observed in connection with “tubular clusters” resembling peripheral reticulum. The distinct crystalline structures located in chloroplasts might be formed by LHC protein aggregates. Smaller crystals of unknown composition were found also in mitochondria. Numerous crystalline cores were present in peroxisomes. The alterations might be the result of imbalance of phytohormone content, degradation effect of CK overproduction, or the example of acclimation to permanent stress.

Bundle sheath chloroplasts of rice are more sensitive to drought stress than mesophyll chloroplasts

We investigated the effects of drought stress on the ultrastructure of chloroplasts in rice plants. After the seedlings were grown in a glasshouse for 1 month, they were treated for drought stress using two methods. One drought treatment was imposed by reducing the water supply to the plants for 1 month. The other was imposed by withholding water for 2 weeks to examine the withering process of leaves by drought stress. The ultrastructural changes of chloroplasts in bundle sheath cells were more prominent than those in mesophyll cells under both drought stress treatments. Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) content in bundle sheath chloroplasts reduced more dramatically than in mesophyll chloroplasts by drought stress. Although a slight swelling of thylakoids was sometimes observed in bundle sheath chloroplasts in moderate stress for 1 month, the thylakoids were less affected by drought stress than chloroplast envelope. These results suggest that chloroplasts in bundle sheath cells were more sensitive to drought stress than those in mesophyll cells and the thylakoids were less damaged by drought stress compared with chloroplast envelope.

Changes of chloroplast ultrastructure and total chlorophyll concentration in cabbage leaves caused by excess of organic Ni(II) complexes

Leaf chlorophyll concentration, chloroplast ultrastructure, Ni concentration in leaves and Ni accumulation in chloroplasts were examined in cabbage plants treated with Ni as organic complexes, i.e. Ni(II)–Glu, Ni(II)–citrate and Ni(II)–EDTA, in the concentrations of 40 and 85 μM. The plants were grown on half-strength Hoagland's nutrient solution at pH 5.3 for a period of 21 days. The Ni(II) complexes have different effects on leaf chlorophyll concentration and degree and specificity of ultrastructural changes of chloroplasts. After Ni(II)–Glu and Ni(II)–citrate treatment at both concentrations of Ni, the leaf chlorophyll concentration was reduced. After Ni(II)–EDTA treatment, it was reduced only at the concentration of 85 μM Ni. After Ni(II)–Glu and Ni(II)–citrate treatment, the electron density of chloroplast stroma and the number of grana were reduced. Accumulation of starch was observed only in those chloroplasts that were located close to vascular bundles. After Ni(II)–Glu treatment, the thylakoids were swollen, but after Ni(II)–citrate treatment, the thylakoids were condensed. After Ni(II)–EDTA treatment, an accumulation of starch and an increase of the number of plastoglobuli were observed. Damage of the thylakoids was observed sporadically. The experiment also showed that there is a relationship between the degree of toxicity of the examined Ni complexes and Ni concentration in leaves. As far as toxicity and Ni bioaccumulation is concerned, the Ni complexes can be put in the following order: Ni(II)–Glu≥Ni(II)–citrate≫Ni(II)–EDTA. The tissue localization of Ni by the silver sulphide method showed differences in Ni accumulation in the chloroplasts. After Ni(II)–Glu and Ni(II)–citrate treatment, Ni accumulation in chloroplasts was higher than after Ni(II)–EDTA treatment.

Influence of nitrogen deficiency on photosynthesis and chloroplast ultrastructure of pepper plants (Research Note)

Pepper plants (Capsicum annuum L. cv. Zlaten Medal) were grown on nutrient solution without nitrogen, and photosynthetic response of plants was examined by determination of leaf CO2 fixation and chlorophyll and carotenoid contents. The absence of nitrogen in the medium resulted in a decrease of the leaf area and of plant biomass accumulation, and in an increase of the root-shoot dry weight ratio. The photosynthetic activity and chlorophyll and carotenoid contents decreased significantly under nitrogen deprivation. Examination of nitrogen deficient leaves by transmission electron microscopy showed dramatic changes in chloroplast ultrastructure. The proportion of starch granules and plastoglobules in the stroma matrix was increased and internal membrane system was greatly reduced. It seems that nitrogen plays an important role in the formation of chloroplast structure and hence to the photosynthetic intensity and productivity of pepper plants.

Changes in chlorophyll, polyamines and chloroplast ultrastructure of Puccinia striiformis induced ‘green islands’ on detached leaves of Triticum aestivum

Biochemical and ultrastructure features of ‘green islands’ were investigated using detached wheat leaves infected with the yellow rust Puccinia striiformis. Chlorophylls appear to culminate 10 d after inoculation at which point ‘green islands’ were fully developed. These changes were paralleled by an increase in spermidine and spermine content which play an important role in formation of ‘green islands’. Retention of chlorophyll was demonstrated in leaf tissues of wheat plants supplied with exogenous putrescine, spermidine and spermine. Putrescine was least and spermidine and spermine most effective in retarding loss of chlorophylls. Ultrastructural observation revealed that chloroplasts were regenerated in ‘green islands’ where many proplastids were detected. The regeneration of chloroplasts coincided with the high concentration of chlorophylls and polyamines particularly spermidine and spermine. The ultrastructural changes of chloroplasts in leaf cell containing infection structures were parallel to physiological changes.

Influence of Drought, High Temperature, and Carbamide Cytokinin 4-PU-30 on Photosynthetic Activity of Plants. 2. Chloroplast Ultrastructure of Primary Bean Leaves

Ultrastructural changes in chloroplasts of primary leaves of 15-d-old bean plants (Phaseolus vulgaris L. cv. Cheren Starozagorski) in response to a single stress (increasing water deficit, WD) as well as to combined stress (WD plus high temperature, WD+HT) were investigated under the possible protective or reparatory effects of the carbamide cytokinin 4-PU-30 [N-(2-chloro-4-pyridyl)-N-phenylurea] applied before or after the stress. Essential structural changes in chloroplast ultrastructure occurred mainly in plants that had experienced WD+HT: the thylakoids were swollen, the envelope was destroyed, and the spatial orientation of inner membrane system was not typical. Changed starch accumulation was also observed. 4-PU-30 protected chloroplast ultrastructure under WD+HT.

Developmental Changes in Chloroplast Ultrastructure and Carbon‐Fixation Metabolism of Dendrobium Flowers (Orchidaceae)

The developmental changes in chloroplast ultrastructure and carbon‐fixation metabolism were studied in flowers of Dendrobium Sonia, an orchid with Crassulacean acid metabolism (CAM). The chloroplasts in the flowers were smaller and had fewer thylakoid membranes and grana than in the leaf. During flower development, the chloroplasts degenerate and become less distinct, with dilated thylakoid membranes. The chlorophyll a/b ratio of the flowers and leaf were similar, while total chlorophyll contents were lower than in the leaf. The total chlorophyll content and the RuBPcase activity in the flowers declined as they matured. In contrast, PEPcase activity increased with flower development. At all stages of flower development, PEPcase/RuBPcase ratios were ca. 10–20‐fold higher than in the leaf. As the flower aged, the PEPcase/RuBPcase ratio increased with decreased rate of 14CO2 fixation. The δ13C values of the flowers were less negative than those of the leaves. Following a 14CO2 feed in the light, a considerable amount of 14C‐metabolites appeared in the organic acids (35%–51%) and sugar (30%–50%) fractions in the flowers. The nocturnal malate increase (NMI) in the flower bud was only 2% of the leaf, and this increased to 14% at the fruit capsule stage. Our results indicate that flowers of Dendrobium Sonia had weak CAM activity in the dark and some degree of β‐carboxylation in the presence of C3 metabolism in the light.

Abscisic acid immunolocalization and ultrastructural changes in water‐stressed lavender (Lavandula stoechas L.) plants

The relationship between the bulk abscisic acid (ABA) content, ABA compartmental redistribution, and chloroplast ultrastructural changes was studied in leaves of lavender (Lavandula stoechas L.) plants subjected to water stress. ABA was uniformly distributed in the cytosol, nucleus, chloroplasts, and cell walls of mesophyll cells in well‐watered plants. In plants subjected to water stress (−2.6 MPa water potential) the bulk leaf ABA increased from 900 to 3 600 pmol g−1 fresh weight. At the ultrastructural level, the first indication of this rise in ABA was a 4‐fold increase in ABA immunolabeling in the cell wall in which the highest labeling values were recorded. This increase in apoplastic ABA in lavender was not attributable to ABA release from the chloroplast, because a simultaneous increase in ABA labeling was observed in both the chloroplast and nucleus (2‐ and 3‐fold, respectively). Water stress induced a progressive increase in bulk leaf ABA concentration to 13 600 pmol g−1 fresh weight coincident, with the highest immunolabeling of ABA in the nucleus and chloroplast. Under severe water stress, the chloroplast membrane broke down, resulting in leakage of ABA from the chloroplast. The stress‐induced increase of ABA in chloroplasts and nuclei may serve a function other than affecting stomatal movement.

Physiological and ultrastructural responses of birch clones exposed to ozone and drought stress

Saplings of birch ( Betula pendula) clones were exposed to drought and ozone stress in controlled chambers and open-field conditions. In the chamber experiment, the plants exposed to high drought stress were more resistant to 130 ppb ozone treatment than the well- and moderately watered plants. On the contrary, in the more realistic field conditions, exposure to low drought stress strengthened the negative effects of slightly elevated ozone. Photosynthetic senescence was delayed despite ozone in drought-stressed plants in the late summer. Specific differences between ozone and drought stress were found particularly in ultrastructural changes of chloroplasts and mitochondria.

Respiratory, Photosynthetic and Ultrastructural Changes Accompanying Salt Adaptation in Culture of Eucalyptus microcorys

Summary Salt tolerant shoot cultures of Eucalyptus microcorys (F. Muell.) were able to grow and tolerate 100 and 150 mmol · L−1 NaCl, where the normal salt sensitive shoots were unable to survive 50 mmol · L−1 NaCl. A comparative study between the salt tolerant and salt sensitive shoots showed that respiration was not significantly different between salt sensitive shoots (without exposure to NaCl) and salt tolerant shoots exposed to 100 and 150 mmol · L−1 NaCl. Photosynthesis on the other hand was significandy increased in salt tolerant shoots when expressed on a chlorophyll basis. However, when respiration or photosynthesis were expressed on a leaf fresh weight basis, both significandy decreased in the salt tolerant shoots compared to the salt sensitive shoots. Photosystem I and ferredoxin NADP-oxidoreductase were relatively insensitive to salt and actually increased in the salt tolerant shoots. Photosystem II and photosystem I+II were not changed significantly when measured on a chlorophyll basis, but did decrease when expressed on a leaf fresh weight basis. Chlorophyll fluorescence parameters such as photochemical efficiency (Fv/Fm) and quantum yield (Y) were increased in salt tolerant shoots exposed to 100 mmol · L−1 NaCl, but were significandy lowered by a salt concentration of 150 mmol·L−1 NaCl. Chloroplast ultrastructural changes were apparent in salt tolerant shoots which included the presence of large starch grains, dilation of the thylakoid membranes, almost no grana were present, and enlarged mesophyll cells. The observations are interpreted in terms of maintenance respiration, photochemical activity, photoassimilation, altered chloroplast membrane structure and starch accumulation.

Effects of Simulated Acid Rain on Chloroplast Ultrastructure of Primary Leaves of Phaseolus Vulgaris

The ultrastructure of chloroplasts in the primary leaf of 10-d-old bean plants (Phaseolus vulgaris L., cv. Cheren Starozagorski) was studied 3, 5, 24, 48, 72 and 168 h after a single treatment with simulated acid rain (pH 2.4, 2.2, 2.0 and 1.8). Different changes in chloroplast structure till full destruction of organelles were traced. A determining factor for these changes was the histological localization of chloroplasts. In the chloroplasts of palisade parenchyma different degrees of expansion of thylakoids (3, 5, and 24 h after the single treatment), and conformational changes of the inner membrane system (48, 72 and 168 h) were observed. The chloroplasts of spongy parenchyma showed a significantly higher degree of structure resistance. The expansion of thylakoids was weak and did not depend on the duration of treatment. The ultrastructural changes of chloroplasts confirmed relative resistance of this species till pH 2.0.

Cadmium-induced ultrastructural changes in chloroplasts of the leaves and stems parenchyma in Myriophyllum spicatum L.

After a 5 d cultivation in solutions with different concentrations of cadmium, changes in chloroplasts of the leaf and stem parenchyma from Myriophyllum spicatum L. were observed: swelling and merging of the grana thylakoids in various degrees, coagulation of the stroma as well as the formation of crystal-like structures in it, accompanied by changes in the plastoglobuli and starch. Concentrations of 3.5 and 6.0 g(Cd2+) m-3 caused a vast destruction of the whole plastid apparatus. Chloroplasts in the parenchyma of stems showed a reduction in the inner membrane system, and an increased number of plastoglobuli. A comparative analysis that we carried out indicated that the changes were not uniform and metal-specific.

Fungi associated with leaf spots of Dracaena ombet (Kotschy and Peyr)

The Dracaena ombet, which is endemic to the Red Sea mountain chain, are now nearly extinct. The combined effect of changes in environmental conditions, both natural and cultural, as well as epidemic fungal infection is identified as the causes of its near disappearance. Nine fungal species were isolated from leaf spots on Dracaena ombet. Cladosporium dracaenatum, Alternaria alternata, Aspergillus niger, Curvularia sp., and Fusarium moniliforme were the most common isolates; while Botrytis cinerea, Helminthosporium sp., Fusarium oxysporum and Epicoccum nigrum were less frequent isolates. The pathogenecity test was carried out for the dominant species, Cladosporium dracaenatum and Alternaria alternata, to detect the compatibility between Dracaena leaves and these pathogens. Scanning and transmission electron microscopy revealed the colonization of these pathogens in leaf tissues of Dracaena. Remarkable ultrastructural changes in chloroplasts, mitochondria, and microbodies of infected cells of Dracaena were noticed.

Ultrastructural Changes in Chloroplasts in Harvested Broccoli Flower Buds During Senescence

Green broccoli (Brassica oleracea L. Italica Group) flower heads were stored in perforated polyethylene bags at 20C. Green color of sepals in broccoli flower buds changed to yellow and individual flower buds wilted gradually during storage. Chlorophyllase activity in flower buds tended to increase and chlorophyll content decreased during senescence. Optical and scanning electron microscopic observations were conducted to elucidate the structural changes of chloroplasts in sepals of broccoli flower buds through the senescence. The chloroplasts observed with optical microscope were fine and green when the stage of broccoli flower buds was all green. However, at half-yellow stage, the shapes of chloroplasts obscured and the green color faded. After this stage, colored small particles appeared in the cells and the number of particles tended to increase as yellowing of the flower buds progressed through the senescence. Scanning electron micrographs indicated that the small particles were formed in the chloroplasts and come out from them with senescence followed by aggregation with each other.