A field experiment was conducted with two cassava cultivars and eight levels of nitrogen to examine the relationship between extractable chlorophyll (Chl) content of cassava leaves and both the Chl meter value (SPAD) and leaf colour chart (LCC) score. The SPAD, LCC, and Chl a+b content were influenced by leaf position, growth stage, cultivar (cv.), and N fertilization. The cvs. and N fertilization had significant effect on SPAD, LCC, and Chl a+b content of youngest fully expanded leaf (leaf 1) blade in most cases. An F-test indicated that common equations pooled across cvs., N fertilization, and growth stages could be used to describe the relationships between Chl a+b content and LCC and between SPAD and LCC, but not between SPAD and Chl a+b content. Relationships between tuber yield and SPAD, LCC, and Chl a+b content were significant (p<0.05) and positive at 30 and 60 d after planting. Thus LCC and SPAD can be used to estimate leaf Chl content which is an indicator of leaf N status. and M. Haripriya Anand, G. Byju.
Photosynthetic pigment contents of the second sexual generation of a cybrid plant (C-18-1) resulting from Solanum nigrum genome and Solanum tuberosum plastome were compared to those of the original (S. nigrum). Chloroplast ultrastructure alterations among S. tuberosum, cybrid, and S. nigrum were also studied. Leaf segments of both the cybrid and S. nigrum plants were cultured on shoot induction medium [B5 supplemented with 0.56 g m-3 benzylaminopurine (BAP)] for one week in light, to induce adventitious bud formation. These leaf segments were then placed in darkness for 5 weeks to form a white shoot. The respective cybrid plant had the same phenotype of the fusion recipient plant (S. nigrum) and was fertile. The rate of photosynthetic pigment biosynthesis in the white cybrid shoots was lower than that of the original plant shoots after subjecting the two plants to the same conditions of different irradiation periods (0, 2, 4, 6, 8, and 10 d). At the 10-d irradiation period of two white shoot plants, the total pigment content of S. nigrum shoot increased approximately 3-fold over that of the cybrid shoot. Numbers of grana and thylakoids as well as chloroplast size were decreased in cybrid cells in comparison to those in S. tuberosum cells. Under atrazine stress, while the chloroplast ultrastructure of the cybrid cells (atrazine sensitive) was strongly influenced, the chloroplasts of S. nigrum (atrazine resistant) were not affected. and K. A. Fayez, A. M. Hassanein.
Chlorophyll (Chl) α fluorescence induction (transient), measured by exposing dark-adapted samples to high light, shows a polyphasic rise, which has been the subject of extensive research over several decades. Several Chl fluorescence parameters based on this transient have been defined, the most widely used being the FV [= (FM-F0)]/FM ratio as a proxy for the maximum quantum yield of PSII photochemistry. However, considerable additional information may be derived from analysis of the shape of the fluorescence transient. In fact, several performance indices (PIs) have been defined, which are suggested to provide information on the structure and function of PSII, as well as on the efficiencies of specific electron transport reactions in the thylakoid membrane. Further, these PIs have been proposed to quantify plant tolerance to stress, such as by high light, drought, high (or low) temperature, or N-deficiency. This is an interesting idea, since the speed of the Chl α fluorescence transient measurement (<1 s) is very suitable for high-throughput phenotyping. In this review, we describe how PIs have been used in the assessment of photosynthetic tolerance to various abiotic stress factors. We synthesize these findings and draw conclusions on the suitability of several PIs in assessing stress responses. Finally, we highlight an alternative method to extract information from fluorescence transients, the Integrated Biomarker Response. This method has been developed to define multi-parametric indices in other scientific fields (e.g., ecology), and may be used to combine Chl α fluorescence data with other proxies characterizing CO2 assimilation, or even growth or grain yield, allowing a more holistic assessment of plant performance., A. Stirbet, D. Lazár, J. Kromdijk, Govindjee., and Obsahuje bibliografické odkazy
Plants of the discovered chlorophyll-deficient mutant of oak (ML) display enhanced disease resistance to the fungus Erysiphe cichoracearum, causal agent of powdery mildew. Quantitative imaging of chlorophyll (Chl) fluorescence revealed that the net photosynthetic rate (PN) declined progressively in both untreated and invaded ML leaves as well as in inoculated wild-type (WT) leaves. Images of non-photochemical fluorescence quenching (NPQ) in both untreated and infected mutant leaves suggested that the capacity of Calvin cycle had been reduced and that there was a complex metabolic heterogeneity within the ML leaf. The ML mutant accumulates reactive oxygen species, ROS (H2O2) from the oxidative burst followed by spontaneous cell death that mimic the hypersensitive response. Reduction in pathogen sporulation on ML leaves correlated with the accumulation of soluble saccharides and a more rapid induction of defence responses including expression of some defence proteins (β-1,3-glucanase and chitinase). Unlike to WT plants, ML- conferred phenotype activates and/or de-represses multiple defence responses, making them more easily induced by pathogens.
Chlorophyllase (Chlase) actívity measured as the in vitro degradation of chlorophyll (Chl) was variably enhanced by various heavy metals (Cd2+, Pb2+, Mn2+, Co^"*", Ni2+ and their mixture). The en2yme actívity on Chl a was higher than that on Chl b. Chlase isolated from Chlorella fusca oř Kirchneriella lunaris responded differently to the heavy metals. The inclusion of Ca2+ in the assay media affected the enzyme actívity. While some concentrations were stimulatory, others were inhibitory depending on partícular heavy metal, the algal species, and the Chl a oř b.
Chlorophyliase (Chlase) is widely distributed in higher and lower plants and differs in activity. It occurs in various organs. In some plants the enzyme is synthesized in cytoplasm, in others in chloroplasts. Various Chlase forms are known. Participation, in the chlorophyll (Chl) degrading systém belongs to the main fimctions of Chlase. Moreover, it may catalyse Chl biosynthesis and takés part in photosynthesis. The Chlase activity is stimulated by radiant energy, sublethal freezing, heavy metals (Hg, Zn, Cu), Fe and Mn deficiency, and mosaic virus infection. The effect of water content on Chlase activity depends on individual plant organs. Osmotic and saline- osmotic stress decreases Chlase activity, but NaCl can stimulate the activity. The influence of plant age depends on plant genus. Some growth regulators (ethylene, heteroauxin, abscisic acid) increase Chlase activity, others (kinetin, dicarboxylic monoesters, gibberellic acid, gibbérellin A3) inhibit it. The mechanisms of Chlase action are also reviewed.
Chloroplasts utilize photons from solar radiation to synthesize energy-rich molecules of ATPs and NADPHs, which are further used in active cellular processes. Multiprotein complexes (MPCs), including photosystems (PSII and PSI), and the cellular architecture responsible for generation of the proton motive force and the subsequent photophosphorylation, mediate the task of ATP and NADPH synthesis. Both photosystems and other multiprotein assemblies are embedded in thylakoid membranes. Advances in techniques used to study structural biology, biophysics, and comparative genomics and proteomics have enabled us to gain insights of structure, function, and localization of each individual component of the photosynthetic apparatus. An efficient coordination among MPCs is essential for normal functioning of photosynthesis, but there are various stressors that might directly or indirectly interact with photosynthetic components and processes. Cadmium is one of the toxic heavy metals that interact with photosynthetic components and damage photosystems and other MPCs in thylakoids. In plants, iron deficiency shows similar symptoms as those caused by Cd. Our article provides a general overview of chloroplast structure and a critical account of Cd-induced changes in photosystems and other MPCs in thylakoids, and suggests the possible mechanisms involved in mediating these changes. The connection between Cd-induced Fe deficiency and the elevated Cd toxicity under the Fe-deficient condition was also discussed., H. Bashir, M. I. Qureshi, M. M. Ibrahim, M. Iqbal., and Obsahuje seznam literatury
A unified multibranched chlorophyll (Chl) biosynthetic pathway is proposed. The proposed pathway takes into account the following considerations: (a) that the earliest putative precursor of monovinyl Chl b that has been detected in higher plants is monovinyl protochlorophyllide b, (b) that in most cases, Chl b biosynthesis has its roots in the Chl a biosynthetic pathway, (c) that the Chl a biosynthetic pathway exhibits extensive biosynthetic heterogeneity, (d) that Chl biosynthesis may proceed differently at different stages of greening and in different greening groups of plants. Integration of the Chl a and b biosynthetic pathways into a unified multibranched pathway offers the functional flexibility to account for the structural and biosynthetic complexity of photosynthetic membranes. In this context, it is proposed that the unified, multibranched Chl a/b biosynthetic pathway represents the template of a Chl-protein biosynthesis center where photosystem (PS) 1, PS2, and light-harvesting Chl-protein complexes are assembled into functional photosynthetic units. The individual biosynthetic routes or groups of two to three adjacent biosynthetic routes may constitute Chl-protein biosynthesis subcenters, where specific Chl-protein complexes are assembled. and C. A. Rebeiz ... [et al.].
Recent experimental evidence (see part 80) suggests that the chlorophyll (Chl) b pathway is biosynthetically heterogeneous. The dissection of this biosynthetic heterogeneity requires the availability of a cell-free system capable of the net synthesis of Chl(ide) a and b. The development of such a system is described. and V. Kolossov ... [et al.].
a1_Photosynthesis is one of the most important processes in plant biology and in the development of new methodologies that allow a better understanding and characterization of the photosynthetic status of organisms, which is invaluable. Flow cytometry (FCM) is an excellent tool for measuring fluorescence and physical proprieties of particles but it has seldom been used in photosynthetic studies and thus the full extent of its potentialities, in this field of research, remains unknown. To determine the suitability of FCM in photosynthesis studies, pea plants were exposed to Paraquat and their status was analyzed during 24 h. FCM was used to evaluate the integrity (volume and internal complexity) and the relative fluorescence intensity (FL) of chloroplasts extracted from those plants. To elucidate which type of information the FL conveys, FL values were correlated with the minimum fluorescence level (F0), maximum fluorescence level (Fm) and maximum photochemical efficiency of PSII (Fv/Fm), obtained by using Pulse-Amplitude-Modulation (PAM) fluorometry. Results indicate that: (1) the biomarkers used to evaluate the structural integrity of the chloroplasts were more sensitive to Paraquat exposure than the ones related to fluorescence; (2) the variation of the chloroplast’s structure, as time progressed, pointed to a swelling and subsequent burst of the chloroplast which, in turn, compromised fluorescence emission; (3) FL presented a high and significant correlation with the Fv/Fm and to a lesser degree with Fm but not with F0; (4) pigment content did not reveal significant changes in response to Paraquat exposure and is in agreement with the proposed model, suggesting that the cause for fluorescence decrease is due to chloroplast disruption., a2_In sum, FCM proved to be an outstanding technique to evaluate chloroplastidal functional and structural status and therefore it should be regarded as a valuable asset in the field of photosynthetic research., E. Rodriguez ... [et al.]., and Obsahuje bibliografii