Structure Of Photosynthetic Apparatus Research Articles

The role of zinc to mitigate heavy metals toxicity in crops

Heavy metal (HM) contamination is a serious concern across the globe, and in recent times, HMs’ intensity has significantly increased, posing a serious threat to crop growth and productivity. Heavy metals pose serious health issues in humans by entering the human food chains. Therefore, it is direly needed to reduce the effects of HMs on plants and humans by adapting appropriate practices. In this context, application of micronutrients can be an essential practice to mitigate the toxic effects of HMs. Zinc (Zn) is a crucial nutrient needed for plant growth, and Zn application reduced the HM-induced toxicity in plants. This review highlights Zn’s role in mitigating the HMs toxicity in plants. We have systematically described the potential mechanisms mediated by Zn to mitigate HMs in plants. Zinc application reduced the HMs uptake and translocation plants, which is considered an essential mechanism of HM stress tolerance. Zn application also improves membrane stability, plant water relationship, nutrient uptake, photosynthetic performance, osmolytes accumulation, anti-oxidant activities, and gene expression. In addition to this, the Zn application substantially improves photosynthesis by enhancing the synthesis of photosynthetic pigments, photosystem activities, enzymatic activities, and maintaining photosynthetic apparatus structure, ensuring better growth under HM stress. Therefore, Zn nutrition could improve the plant performance under HM stress by modulating the plant’s physiological and biochemical functioning, anti-oxidant activities, osmolytes accumulation, and gene expression.

Effects of Burkholderia thailandensis rhamnolipids on the unicellular algae Dunaliella tertiolecta

The effects of rhamnolipids (RLs) produced and further purified from Burkholderia thailandensis, on the unicellular microalgae Dunaliella tertiolecta were investigated, in terms of RLs ability to affect algal growth, photosynthetic apparatus structure and energy flux, round and through photosystems II and I. Specifically, 24–48 h RLs-treated algae (RLs at concentrations ranged from 5 to 50 mg L−1) showed significantly decreased levels of growth rate, while increased levels of Chl a and b were obtained only in 72–96 h RLs-treated algae. Similarly, although no changes were obtained in the Chl a/b ratio and almost all chlorophyll fluorescence parameters over time, yields of electron transport (ϕR0, ϕE0) and respective performance index (PItotal) were negatively affected at 72 and 96 h. Based on those findings, it seems that the inhibitory effect of RLs on the algae growth rate after 24 and 48 h and the gradual attenuation of the phenomenon (after 72 h of exposure), may indicate the initial response of the organism, as well as algae ability to overcome, since RLs showed no effects on algae photosynthetic ability. Those findings reveal for the first time that RLs from Burkholderia thailandensis are not harmful for Dunaliella tertiolecta. However, further studies with the use of more aquatic species could be essential for assessing the RLs-mediated effects on aquatic biota.

Mathematical model for controlling CO2 concentration in greenhouses late in MATLAB

The article is devoted to the development of an automated control system for irradiation facilities. The system will optimize the electricity cost for supplementary lighting plants in greenhouses without economic losses. A number of scientific researches studying chlorophyll, photosynthesis and processes in the green plant leaf were analyzed as the theoretical base for the present article. On their basis, a schematic structure of the photosynthetic apparatus of plants was developed and kinetic differential equations describing the structure and functioning of the photosynthetic chlorophyll apparatus of green plants were derived. The obtained mathematical expressions describe the changes in the concentrations of the base materials that participate in the formation of the photosynthetic apparatus structure and the accumulation of photosynthesis products and allow effective controlling of the irradiation process of plants. It has been achieved by adjusting the parameters of the illumination interval and the illumination area with the aid changing the number of switched on and off sources of optical radiation and changing the spectral component in a narrow limit.

Influence of High Temperature on Photosynthesis, Antioxidative Capacity of Chloroplast, and Carbon Assimilation among Heat-tolerant and Heat-susceptible Genotypes of Nonheading Chinese Cabbage

High temperature (HT) is a major environmental stress limiting oversummer production of nonheading Chinese cabbage (NHCC, Brassica campestris ssp. chinensis Makino). In the present study, the effects of HT on photosynthetic capacity, including light reaction and carbon assimilation, were completely investigated in two NHCC, ‘xd’ (heat-tolerant), and ‘sym’ (heat-susceptible). The two genotypes showed significant differences in plant morphology, photosynthetic capacity, and photosynthate metabolism (carboassimilation). HT caused a decrease in photosynthesis, chlorophyll contents, and photochemical activity in NHCC. However, these main photosynthetic-related parameters, including net photosynthetic rate (PN), maximal photochemical efficiency of PSII (Fv/Fm), and total chlorophyll content in ‘xd’, were significantly higher than those of ‘sym’ plants. The antioxidant contents and antioxidative enzyme activities of ascorbic acid-reduced glutathione cycle in the chloroplast of ‘xd’ were significantly higher than those of ‘sym’. Microscopic analyses revealed that HT affected the structure of photosynthetic apparatus and membrane integrity to a different extent, whereas ‘xd’ could maintain a better integrated chloroplast shape and thylakoid. Inhibited light reaction also hampered carbon assimilation, resulting in a decline of carboxylation efficiency and imbalance of carbohydrate metabolism. However, larger declined extents in these data were presented in ‘sym’ (heat-susceptible) than ‘xd’ (heat-tolerant). The heat-tolerant genotype ‘xd’ had a better capacity for self-protection by improved light reaction and carbon assimilation responding to HT stress.

Bottle gourd rootstock-grafting promotes photosynthesis by regulating the stomata and non-stomata performances in leaves of watermelon seedlings under NaCl stress

Previously, we found that the amelioration of photosynthetic capacity by bottle gourd (Lagenaria siceraria Standl.) rootstock in watermelon seedlings (Citrullus lanatus [Thunb.] Mansf.) with salt treatment might be closely related to the enzymes in Calvin cycle such as ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) (Yang et al., 2012). We confirmed this and showed more details in this study that improved photosynthesis of watermelon plants by bottle gourd rootstock was associated with the decreased stomata resistance and the increased photochemical activity and photosynthetic metabolism with or without 100mM NaCl stress for 3 days. The analysis of gas exchange parameters showed that self-grafted plants suffered serious non-stomatal limitation to photosynthesis under salt stress while rootstock-grafted plants were mainly affected by stomata limitation in stress conditions. Further, results showed that NaCl stress markedly reduced the chlorophyll content, damaged the structure of photosynthetic apparatus, and inhibited photochemical activity and CO2 assimilation in self-grafted plants. In contrast, rootstock-grafting increased the chlorophyll content, especially chlorophyll b, and minimized the harmful effects on photosystem II (PSII) reaction center and the thylakoids structure induced by NaCl stress. Furthermore, rootstock-grafting enhanced the content and activity of Rubisco and thus elevated carbon fixation in the leaves of watermelon scions under salt stress. The gene expressions of enzymes related to ribulose-1,5-bisphosphate (RuBP) regeneration were also up-regulated by rootstock and this probably guaranteed the sufficient supply of RuBP for the operation of Calvin cycle in watermelon scions under salt stress. Thus, bottle gourd rootstock promoted photosynthesis by the activation of stomatal and non-stomatal abilities, especially the regulation of a variety of photosynthetic enzymes, including Rubisco in grafted watermelon plants under NaCl stress.

Chemical composition of leaves and structure of photosynthetic apparatus in aquatic higher plants

Chemical composition of leaves (the content of carbon, nitrogen, nonstructural carbohydrates, organic acids, mineral substances, and water) and the structure of photosynthetic apparatus (specific leaf weight, cell volume, and the number of cells per unit leaf area) were investigated for 18 species of aquatic plants featuring various degrees of contact with aqueous environment and sediment. The rooted hydrophytes with floating leaves were characterized by comparatively high content of carbon and nitrogen (437 and 37 mg/g dry wt, respectively) and by low concentration of nonstructural carbohydrates, mineral substances, and organic acids (161, 54, and 60 mg/g dry wt, respectively). Unlike rooted plants, the free-floating nonrooted hydrophytes had characteristically higher content of nonstructural polysaccharides and mineral substances (by a factor of 1.3 and 1.6, respectively), while the leaf nitrogen content was 1.4 times lower, and the proportion of soluble carbohydrates in the total content of nonstructural carbohydrates was rather low (9%). The chemical composition of leaves in submerged rooted hydrophytes was intermediate between those for rooted hydrophytes with floating leaves and for nonrooted free plants. We found reliable positive correlations between the volume of photosynthesizing cells and the leaf content of organic acids (r = 0.69), as well as between specific leaf weight, the number of photosynthesizing cells per unit leaf area, and carbon content (r = 0.67 and r = 0.62, respectively). The content of nitrogen and nonstructural carbohydrates in hydrophytes was unrelated to structural characteristics of photosynthetic apparatus and depended on the absence or presence of plant attachment to the sediment. It is concluded that the structural traits of photosynthetic apparatus and the leaf chemical composition in hydrophytes featuring different degrees of plant contact with water and sediment reflect the specificity of plant adaptation to complex conditions of their habitats.

The search for an optimal orientational ordering of Q y transition dipoles of subantenna molecules in the superantenna of photosynthetic green bacteria: Model calculations

This work continues a series of our investigations on efficient strategies of functioning of natural light-harvesting antennae, initiated by our concept of rigorous optimization of photosynthetic apparatus structure by functional criterion. Using computer modeling for the functioning of the natural antennae, we suggested some basic principles for designing optimal model systems. Targeted searches for these principles in in vivo systems allowed us to recognize some of them in natural antennae. This work deals with the problem of the structure optimization of nonuniform superantennae of photosynthetic green bacteria. These superantennae consist of several uniform subantennae which produces a problem of their optimal coordination. In this work, we used mathematical modeling for the functioning of these natural superantennae to consider a possible way to optimize the superantenna structure using optimization of mutual spatial orientation of Qy transition dipoles of subantennae pigments. This allowed us to determine some modes of optimal orientational ordering of Qy transition dipoles of subantennae pigments in the model of the green bacterium Chloroflexus aurantiacus superantenna. It was shown that the optimal mutual orientation of Qy transition dipoles of subantennae pigments (resulting in stable minimizing of the energy transfer time within the superantenna and, as a consequence, in decrease in energy losses) ensures the high efficiency and stability of the superatenna functioning.

Photosynthetic performance in Syringodiumfiliforme: seasonal variation in light-harvesting characteristics

Syringodium filiforme does not exhibit physiological compensation as a function of season. This has important implications with respect to the diversity and spatial distribution of seagrass species, with Syringodium-like physiological characteristics, that are exposed to chronic low light conditions common to estuarine environments. Adult Syringodium filiforme plants were sampled at bimonthly intervals between August 1996 and August 1997 from a site in Lower Laguna Madre, Texas with a mean depth of ∼1.2 m. Photosynthesis-irradiance (PI) experiments were conducted at ambient temperatures, in conjunction with measurements of reaction center density and size, to characterize photosynthetic apparatus structure and performance. Values for relative quantum yield ( α; O 2 evolved per incident photon), compensation point ( I c), saturation point ( I k), dark respiration ( R d) and light-saturated photosynthesis ( P max), collected during late summer 1996, exhibited no significant differences from those collected in late spring 1997. Changes in pigment concentration, exhibiting no distinct seasonal pattern, were manifested in adjustments of both photosystem density and size. Densities for photosystem I (PSI) were highest during winter months (ca. 0.5 pmol mm −3); densities for photosystem II (PSII) exhibited no seasonal trend, ranging from 0.2 to 0.7 pmol mm −3. Little variation was noted regarding the size of PSI (PSU P700), whereas, size estimates for PSII (PSU O 2 ) were largest during winter and early-spring (ca. 5400 Chl- a P680 −1). These data indicate that S. filiforme may have some capacity for altering photosynthetic apparatus structure. However, since α, I c and I k did not change with season, the benefit of such adjustments is not obvious. We suggest photophysiological parameters may not be reliable indicators of environmental stress in Syringodium filiforme, as this species does not exhibit a great potential for phenotypic plasticity. This work serves as a basis for future studies designed to address physiological compensation in seagrasses and the ability of coastal macrophytes to respond to environmental change (e.g. reductions in light availability).

Generic characters of the simplest cyanoprokaryotes Cyanobium, Cyanobacterium and Synechococcus

The cytomorphological features (cell morphology, type of cell division, cell structure, structure of photosynthetic apparatus) were studied in the type strains of the cyanoprokaryotic genera Cyanobium and Cyanobacterium, and in the reference strain of the traditional genus Synechococcus ( Synechococcus PCC 6301; = “ Anacystis nidulans” sensu auct.). They were originally described by Rippka & Cohen-Bazire, based on the mean DNA-base composition (moles % G + C) and on the resistance to various cyanophages. The phenotypic diacritical characters were found to coincide well with the molecular markers, and thus, the genera Cyanobium and Cyanobacterium are acceptable also according to the traditional (botanical) taxonomic criteria. The integrated molecular, cytomorphological and ecophysiological approaches to the solution of taxonomic problems in cyanobacteria are therefore inevitable for taxonomic evaluation, from the methodological point of view. The lists of species within the revised genera Cyanobium and Cyanobacterium are reviewed.

Characterization of Photosynthetic Apparatus of Pea Chlorophyll Mutants and their Heterotic F1 Hybrids with Standard Genotype (cv. Torsdag)

In comparison to cv. Torsdag, in leaves of low-productive Pisum sativum L. chlorophyll mutants the decrease in chlorophyll content was caused by the decrease in cell number per unit volume. Qualitative changes in activities of photosystem (PS) 1 in mutant M2004, and quantitative changes of PS1 and PS2 in mutants M2004 and M2014 and in hybrids were also found. However, the activity of ribulose-1,5-bisphosphate carboxylase (RuBPC) in M2014, and those of RuBPC and glyceraldehyde phosphate dehydrogenase in M2004 and hybrids were higher than in cv. Torsdag. The hybrids inherited the normal structure of photosynthetic apparatus of standard genotype in parallel with the compensatory gene complex of M2004, which was expressed at many levels of organization. This may be the basis of hybrid vigour in this case.

Changes in the antenna size of Photosystem I and Photosystem II in Synechococcus sp. strain PCC 7942 grown in the presence of SANDOZ 9785 ? a Photosystem II inhibitor

SANDOZ 9785, also known as BASF 13.338, is a pyridazinone derivative that inhibits Photosystem II (PS II) activity leading to an imbalance in the rate of electron transport through the photosystems. Synechococcus sp. strain PCC 7942 cells grown in the presence of sublethal concentration of SANDOZ 9785 (SAN 9785) for 48 hours exhibited a 20% decrease in Chl a per cell. However, no changes were observed in the content of phycocyanin per cell, the size of the phycobilisomes or in the PS II:PS I ratio. From an estimate of PS II electron transport rate under varying light intensities and spectral qualities and analysis of room temperature Chl a fluorescence induction, it was deduced that growth of Synechococcus PCC 7942 in the presence of SAN 9785 leads to a redistribution of excitation energy in favour of PS II. Though the redistribution appears to be primarily caused by changes affecting the Chl a antenna of PS II, the extent of energetic coupling between phycobilisomes and PS II is also enhanced in SAN 9785 grown Synechococcus PCC 7942 cells. There was a reduction in the effective size of PS I antenna based on measurement of P700 photooxidation kinetics. These results indicate that when PS II is partially inhibited, the structure of photosynthetic apparatus alters to redistribute the excitation energy in favour of PS II so that the efficiency of utilization of light energy by the two photosystems is optimized. Our results suggest that under the conditions used, drastic structural changes are not essential for redistribution of excitation energy between the photosystems.