Degree Of Thylakoid Stacking Research Articles

Multivariate Statistical Analysis of Low-Light Tolerance in Tomato (Solanum lycopersicum Mill.) Cultivars and Their Ultrastructural Observations

This research used multivariate statistical analysis to evaluate the tolerance of 11 tomato cultivars to low light at the seedling stage. The low-light condition (200–420 μmol/m2 s) was simulated by a shade net. It was found that 11 of 16 character indices of different cultivars, such as dropping angle, bend degree, and accumulation of leaf area, showed a significant difference by using multiple variance analysis. After factor analysis, the 11 character indices could be summarized into 5 main factors with a cumulative contribution rate of 84.968 %. According to the factor scores after varimax rotation, the 11 tomato cultivars could be classified into three categories by using cluster analysis. The severely low-light-sensitive cultivars were T1, T5, T6, T10, and T11 and the moderately low-light-sensitive cultivars were T4, T7, and T9. Cultivars T2, T3, and T8 were resistant to low light. In accordance with the appraisal result, the light-sensitive cultivars T5 and T10, the moderately low-light-sensitive cultivar T4, and the low-light-tolerant cultivar T8 were randomly selected to observe the variation in the ultrastructure of leaves of different tomato cultivars with the aid of a transmission electron microscope (TEM). In chloroplasts of T5 and T10, membranes were heavily damaged and mitochondria were vacuolated, whereas the chloroplast structure of T4 was slightly damaged and its mitochondria grew normally. In the chloroplasts of T8, the organelle membranes were intact, the degree of thylakoid stacking was high, and mitochondria grew normally. Our results showed that multivariate statistical analysis of low-light tolerance in tomatoes has certain scientific applicability.

Effects of natural ventilation on leaf ultrastructure of Dianthus caryophyllus L. cultured in vitro

Vessel closure configurations exert direct and indirect control over factors pertaining to the physical boundaries of the mieroenvironment, and induce a typical phenotype in in vitro plant production. Upon modification of the in vitro environment, carnation explants showed a gradation of their ultrastructural characteristics from hyperhydric to normal. A higher degree of development was observed in plants from vessels with higher ventilation compared to ones from vessels with low ventilation rates. The cell walls of epidermal cells from both normal and hyperhydric plants grown in nonventilated vessels were less developed than those from plants grown in ventilated vessels. Cytoplasm of normal plants was dense and generally located in parietal areas. The cytoplasm was even more dense in plants grown in ventilated vessels and acclimated. The degree of thylakoid stacking and distribution were affected by ventilation conditions, being poorly developed with low ventilation. Ultrastructurally, stomata from in vitro plants are ready to carry out their task, although there are significant differences in guard cell size and vacuolar area between acclimated and in vitro plants.

Photosynthetic and structural acclimation to light direction in vertical leaves of Silphium terebinthinaceum.

The azimuth of vertical leaves of Silphium terebinthinaceum profoundly influenced total daily irradiance as well as the proportion of direct versus diffuse light incident on the adaxial and abaxial leaf surface. These differences caused structural and physiological adjustments in leaves that affected photosynthetic performance. Leaves with the adaxial surface facing East received equal daily integrated irradiance on each surface, and these leaves had similar photosynthetic rates when irradiated on either the adaxial or abaxial surface. The adaxial surface of East-facing leaves was also the only surface to receive more direct than diffuse irradiance and this was the only leaf side which had a clearly defined columnar palisade layer. A potential cost of constructing East-facing leaves with symmetrical photosynthetic capcity was a 25% higher specific leaf mass and increased leaf thickness in comparison to asymmetrical South-facing leaves. The adaxial surface of South-facing leaves received approximately three times more daily integrated irradiance than the abaxial surface. When measured at saturating CO2 and irradiance, these leaves had 42% higher photosynthetic rates when irradiated on the adaxial surface than when irradiated on the abaxial surface. However, there was no difference in photosynthesis for these leaves when irradiated on either surface when measurements were made at ambient CO2. Stomatal distribution (mean adaxial/abaxial stomatal density = 0.61) was unaffected by leaf orientation. Thus, the potential for high photosynthetic rates of adaxial palisade cells in South-facing leaves at ambient CO2 concentrations may have been constrained by stomatal limitations to gas exchange. The distribution of soluble protein and chlorophyll within leaves suggests that palisade and spongy mesophyll cells acclimated to their local light environment. The protein/chlorophyll ratio was high in the palisade layers and decreased in the spongy mesophyll cells, presumably corresponding to the attentuation of light as it penetrates leaves. Unlike some species, the chlorophyll a/b ratio and the degree of thylakoid stacking was uniform throughout the thickness of the leaf. It appears that sun-shade acclimation among cell layers of Silphium terebinthinaceum leaves is accomplished without adjustment to the chlorophyll a/b ratio or to thylakoid membrane structure.

Seasonal variation in the photosynthetic capacity of a willow (Salix cv. Aquatica gigantea) canopy. 2 Comparison of the structure and function of chloroplasts at different levels in the canopy.

Development of leaf chloroplast ultrastructure at five levels in a willow (Salix cv. Aquatica gigantea) canopy was followed during one growing season in the field. Changes in chloroplast ultrastructure were compared with the rate of CO(2) uptake of the same leaves. The highest rates of CO(2) uptake were recorded in young leaves exposed to full available sunlight. In these leaves, the area of the grana stacks was less than 20% of the total chloroplast area and the degree of thylakoid stacking was less than 1.5. The chloroplasts of these leaves contained large amounts of starch and small amounts of plastoglobuli. As the canopy grew and the leaves in the lower parts of the canopy became shaded, the structure of the chloroplast thylakoids gradually changed. In leaves at the two lowest levels of the canopy, the degree of stacking at the end of the growing season was close to 2 and correspondingly the rate of CO(2) uptake was low. The areas of grana stacks and plastoglobuli in these chloroplasts increased and were about 30 and 10% of the chloroplast area, respectively, by the end of the growing season. The increase in the degree of thylakoid stacking was caused by increased biosynthesis of grana lamellae, which in general were thinner than the lamellae of young leaves. The length of the stroma lamellae did not change with leaf age. Morphometric measurements showed that the structure of the chloroplasts in leaves 160 cm above ground was dynamic and responsive to environmental conditions so that photosynthetic capacity remained high for 7 weeks despite an increase in leaf shading.

Influence of structural and physical properties of the thylakoid membrane on QA - oxidation

Using isolated pea thylakoids, the relative rate of QA (-) oxidation has been estimated under various conditions, from the restoration of the induction curves following a dark period and from light 1-induced changes in modulated chlorophyll fluorescence excited by light 2.Alterations of QinfA (sup-) oxidation rates were observed under conditions which affected the degree of thylakoid stacking, the lipid fluidity and the integrity of the membranes. The results are discussed in terms of the interactions between QA (-) and the plastoquinone pool with particular emphasis on lateral diffusion.

Correlation between thylakoid stacking and cation-induced decrease in photosystem I electron transport at saturating light intensity

A Mg 2+-induced decrease of the rate of photosystem I (PS I) electron transport (DCIPH 2 → methyl viologen) in thylakoids under saturated light intensities has been reported earlier (S. Bose, J. E. Mullet, G. E. Hoch, and C. J. Arntzen, 1981, Photobiochem. Photobiophys. 2, 45–52). A similar effect is observed with Na +, although the concentration required for half-maximal inhibition was higher by about two orders of magnitude. The cation effect was gradually abolished as the thylakoids were aged by incubation at 30 °C for 6 h. The loss of cation effect on PS I electron transport rate during aging was parallel to the corresponding loss of cation effect on thylakoid stacking. The cation concentration required for thylakoid stacking and the degree of inhibition as a function of cation concentration correlated strongly with the degree of thylakoid stacking. These observations indicated that the inhibition of the rate of PS I electron transport by cations is a consequence of cation-induced stacking of thylakoid membranes. The observed inhibition of the rate of PS I electron transport is discussed in terms of two hypotheses: (i) a fraction (20–30%) of the PS I complexes is trapped in the appressed region of grana and becomes unavailable to the electron donor (DCIPH 2) and (ii) the membrane structure is altered by the cations in such a manner that the rate constant of electron donation by the donor to the electron transport chain in the thylakoid is decreased.

Chlorophyll‐protein levels and degree of thylakoid stacking in radish chloroplasts from high‐light, low‐light and bentazon‐treated plants

The level of 7 chlorophyll‐carotenoid‐proteins was determined in chloroplasts from radish seedlings (Raphanus sativusL. var. Saxa Treib) grown in high‐light (HL; 90 W m−2and low‐light (LL; 10 W m−2) growth conditions with and without application of the photosystem 2 herbicide bentazon (10−4M) and compared with the degree of thylakoid stacking.The photosynthetic apparatus of HL‐chloroplasts contains higher proportions of the photosystem 1 chlorophylla‐proteins CPI and CPIa than LL‐chloroplasts or chloroplasts from bentazon‐treated plants.In LL‐chloroplasts and in chloroplasts from bentazon‐treated plants a higher proportion of light‐harvesting chlorophylla/b‐proteins (LHCP1, LHCP2, LHCP3, LHCPy) is found. Bentazon treatment changes the proportion of LHCPs to about the same levels under both HL and LL‐growth conditions. The amounts of free chlorophyll found in bentazon chloroplasts (27–29%) is higher than in the HL or LL‐controls (16–18%).The increase in degree of thylakoid stacking (% proportion of appressed membranes per total chloroplasts membranes) of LL‐chloroplasts as compared to HL‐chloroplasts of 7 to 9% (3rd to 5th day of illumination) is paralleled by a similar increase in the LHCPs of 5% and 8% (3rd and 5th day). The importance of light harvesting chlorophylla/b‐proteins as a prerequisite for thylakoid stacking is discussed.

State 1-state 2 transition in leaves and its association with ATP-induced chlorophyll fluorescence quenching

By using chlorophyll fluorescence, a study has been made of changes in spillover of excitation energy from Photosystem (PS) II to PS I associated with the State 1–State 2 transition in intact pea and barley leaves and in isolated envelope-free chloroplasts treated with ATP. (1) In pea leaves, illumination with light preferentially absorbed by PS II (Light 2) led to a condition of maximum spillover (state 2) while light preferentially absorbed by PS I induced minimum spillover condition (State 1) as judged from the redox state of Q and low-temperature emission spectra. The State 1–State 2 transitions took several minutes to occur, with the time increasing when the temperature was lowered from 19 to 6°C. (2) In contrast to the wild type, leaves of a chlorophyll b-less mutant barley did not exhibit a State 1–State 2 transition, suggesting the involvement of the light-harvesting chlorophyll a b- protein complex in spillover changes in higher plants. (3) Spillover in isolated pea chloroplasts was increased by treatment with ATP either (a) in Light 2 in the absence of an electron acceptor or (b) in the dark in the presence of NADPH and ferredoxin. These observations can be interpreted in terms of the model that a more reduced state of plastoquinone activates the protein kinase which catalyzes phosphorylation of the light-harvesting chlorophyll a b- protein complex (Allen, J.F., Bennett, J., Steinback, K.E. and Arntzen, C.J. (1981). Nature 291, 25–29). This process was found to be very temperature sensitive. (4) Pea chloroplasts illuminated in the presence of ATP seemed to exhibit a slight decrease in the degree of thylakoid stacking, and an increased intermixing of the two photosystems. (5) The possible mechanism by which protein phosphorylation regulates the State 1–State 2 changes in intact leaves is presented in terms of changes in the spatial relationship of two photosystems resulting from alteration in membrane organization.

Change of Chloroplast Ultrastructure in Radish Seedlings under the Influence of the Photosystem II-Herbicide Bentazon

The influence of the photosystem II-herbicide bentazon on the ultrastructure of chloroplasts of radish seedlings (Raphanus sativus L.) was investigated with special emphasis on thylakoid development and grana formation. Bentazon application (10-3 ᴍ) induces the formation of broader and higher grana stacks (grana width: 0.5-0.6 μm; greatest frequency: 3-8 thylakoids per granum) than in the control plants (grana width: 0.3 μm; greatest frequency: 2-4 thylakoids per granum). Furthermore, the amount of chloroplast lamellae is enhanced, as are the stacking degree of thylakoids and the grana area. The chloroplasts of bentazon-treated plants appear to be shorter and thicker than in the controls and show all signs of a shade-type adaptation of the photosynthetic apparatus.

The cyclic variation in the thylakoid aggregation in normal and calcium deficient cells ofScenedesmus

Synchronized cultures ofScenedesmus obtusiusculus Chod. grown in media with and without calcium supply have been studied in the electron microscope. There is a cyclic variation in the stacking of thylakoids in cells grown in the presence of calcium. The degree of thylakoid aggregation and the frequency of single thylakoids increase during the dark period of the cell cycle. In calcium deficient cells a cyclic variation is also present, but the degree of thylakoid stacking and the frequencies of cells with granum-like aggregates and single thylakoids are higher than in the + Ca-cells.