Pigments absorbing 350-1,050 nm radiation have had an important role on the Earth for at least 3.5 billion years. The ion pumping rhodopsins absorb blue and green photons using retinal and pump ions across cell membranes. Bacteriochlorophylls (BChl), absorbing in the violet/blue and near infra red (NIR), power anoxygenic photosynthesis, with one photoreaction centre; and chlorophylls (Chl), absorbing in the violet/blue and red (occasionally NIR) power oxygenic photosynthesis, with two photoreaction centres. The accessory (bacterio)chlorophylls add to the spectral range (bandwidth) of photon absorption, e.g., in algae living at depth in clear oceanic water and in algae and photosynthetic (PS) bacteria in microbial mats. Organism size, via the package effect, determines the photon absorption benefit of the costs of synthesis of the pigment-protein complexes. There are unresolved issues as to the evolution of Chls vs. BChls and the role of violet/blue and NIR radiation in PS bacteria., A. W. D. Larkum, R. J. Ritchie, J. A. Raven., and Obsahuje bibliografické odkazy
Genotypic variations were observed among 6 variants and an indigenous one as a control. An efficient genotype OCD(L) of Ocimum sanctum had the greatest content of chlorophylls [2.15 g kg-1(FM)], Chl a/b ratio of 1.86, net photosynthetic rate of 0.72 mg(CO2) m-2 s-1, and 1.56 % oil formation. Methyl chavicol formed 50.31 % of total oil in OSP-6 genotype, which had also maximum peroxidase activity [ΔOD 2.4 mg-1(protein)] and maximum production of eugenol (30.44 % of total oil). We found an oxido-reducible reaction of peroxidase and high bands of peroxidase isoenzymes in this OSP-6 genotype for the formation of monoterpene essential oil(s) and possibly the major constituents of eugenol through the high production of photosynthates. and A. Misra ... [et al.].
Three-year-old plants of Parthenium argentatum Gray cv. 11591 grown under natural photoperiod were exposed for 60 d to low night temperature (LNT) of 15 °C (daily from 18:00 to 06:00). Effects of the treatment on net photosynthetic rates (PN), rubber accumulation, and associated biochemical traits were examined. LNT initially reduced PN with a parallel decline in the activities of ribulose-1,5-bisphosphate carboxylase, fructose bisphosphatase, and sucrose phosphate synthase for 20-30 d. Later, LNT enhanced PN and the activities of photosynthetic enzymes. Associated with high PN in LNT-treated guayule plants was a two-fold increase in rubber content and rubber transferase activity per unit of protein. The initial decrease in PN in LNT-treated guayule was associated with low content of chlorophyll (a+b), large starch accumulation, and higher ratio of glucose-6-phosphate/fructose-6-phosphate. Photosystem 2 activity in isolated chloroplasts was initially decreased, but increased after 30 d. There was a significant increase in the leaf soluble protein content in LNT-treated plants. Hence the photosynthetic performance of plants grown at 15 °C night temperature for 50 d was superior to those grown under natural photoperiod in all parameters studied. The high photosynthetic capacity may contribute to superior rubber yields under LNT. and D. Sundar, A. Ramachandra Reddy.
Maize plants of CPB2 and CPB8 hybrids were kept under water deficit for 22 d. In the CPB8 hybrid, leaf rolling initiated at the 9th d of water deficit period, while in CPB2 hybrid it was at the 15th d. Both hybrids showed leaf rolling initiation at the same leaf water potential, ΨW of -0.480±0.095 MPa. At leaf rolling initiation, the leaf osmotic potential, ΨS was -0.730±0.085 MPa in CPB8 and 0.630±0.110 MPa in CPB2. The leaf temperature and stomatal conductance were higher in CPB8 than in CPB2. Values of leaf ΨW, ribulose-1,5-bisphosphate carboxylase activity, chlorophyll content, and specific leaf area were similar in both hybrids. Phosphoenolpyruvate carboxylase activity and protein content were lower in the CPB2 hybrid than in CPB8. In both hybrids leaf rolling initiation was associated with: (1) higher leaf temperature, with leaf rolling effect related to leaf temperature reduction, and (2) lower leaf ΨS, related to osmotic adjustment as an additional component of drought-tolerance strategy. and D. Fernandez, M. Castrillo.
Mutants with altered leaf morphology are useful as markers for the study of genetic systems and for probing the leaf differentiation process. One such mutant with deficient greening and altered development of the leaf mesophyll appeared in an inbred line of sunflower (Helianthus annuus L.). The objectives of the present study were to determine the inheritance of the mutant leaf trait and its morphological characterisation. The mutation, named mesophyll cell defective1 (mcd1), has pleiotropic effects and it is inherited as a monogenic recessive. The structure and tissue organization of mcd1 leaves are disrupted. In mcd1 leaves, the mesophyll has prominent intercellular spaces, and palisade and spongy tissues are not properly shaped. The mutant palisade cells also appear to be more vacuolated and with a reduced number of chloroplasts than the wild type leaves of equivalent developmental stage. The lamina thickness of mcd1 leaves is greatly variable and in some areas no mesophyll cells are present between the adaxial and abaxial epidermis. The leaf area of the mcd1 mutant is extremely reduced as well as the stem height. A deficient accumulation of photosynthetic pigments characterizes both cotyledons and leaves of the mutant. In mcd1 leaves, chlorophyll (Chl) fluorescence imaging evidences a spatial heterogeneity of leaf photosynthetic performance. Little black points, which correspond to photosystem II (PSII) maximum efficiency (Fv/Fm) values close to zero, characterize the mcd1 leaves. Similarly, the lightadapted quantum efficiency (ΦPSII) values show a homogeneous distribution over wild type leaf lamina, while the damaged areas in mcd1 leaves, represented by yellow zones, are prominent. In conclusion, the loss of function of the MCD1 gene in Helianthus annuus is correlated with a variegated leaf phenotype characterized by a localized destruction of mesophyll morphogenesis and defeat of PSII activity. and M. Fambrini ... [et al.].
Winter wheat plants were grown in open top chambers either at 365 µmol mol-1 (AC) or at 700 µmol mol-1 (EC) air CO2 concentrations. The photosynthetic response of flag leaves at the beginning of flowering and on four vertical leaf levels at the beginning of grain filling were measured. Net photosynthetic rates (PN) were higher at both developmental phases in plants grown at EC coupled with larger leaf area and photosynthetic pigment contents. The widely accepted Farquhar net photosynthesis model was parameterised and tested using several observed data. After parameterisation the test results corresponded satisfactorily with observed values under several environmental conditions. and N. Harnos, Z. Tuba, K. Szente.
Non-destructive and rapid method for assessment of leaf photosynthetic characteristics is needed to support photosynthesis modelling and growth monitoring in crop plants. We determined the quantitative relationships between leaf photosynthetic characteristics and canopy spectral reflectance under different water supply and nitrogen application rates. The responses of reflectance at red radiation (wavelength 680 nm) to different water contents and nitrogen rates were parallel to those of leaf net photosynthetic rate (PN). The relationships of reflectance at 680 nm and ratio index of R(810,680) (near infrared/red, NIR/R) to PN of different leaf positions and leaf layers in rice indicated that the top two full leaves were the best leaf positions for quantitative monitoring of leaf PN with remote sensing technique, and the ratio index R(810,680) was the best ratio index for evaluating leaf photosynthetic characteristics in rice. Testing of the models with independent data sets indicated that R(810,680) could well estimate PN of top two leaves and canopy leaf photosynthetic potential in rice, with the root mean square error of 0.25, 0.16, and 4.38, respectively. Hence R(810,680) can be used to monitor leaf photosynthetic characteristics at different growth stages of rice under diverse growing conditions. and Y. Tian, Y. Zhu, W. Cao.
This study aimed to investigate the effects of waterlogging on the growth and photosynthetic characteristics of paired near-isogenic lines of waterlogging-tolerant (Zz-R) and waterlogging-sensitive
(Zz-S) waxy corn inbred line seedlings. All plants were grown until the fifth leaves were fully expanded. Subsequently the plants in the pots were submerged in water for 4 d. During the waterlogging period, morphological and photosynthetic parameters related to waterlogging tolerance were examined. After 4 d, a significant decrease was observed in shoot and root fresh mass, net photosynthetic rate, stomatal conductance, transpiration, water-use efficiency, light-saturation point, maximal photosynthetic rate, apparent quantum yield, maximal quantum yield of PSII, and effective quantum yield of PSII photochemistry in waterlogged plants of both genotypes. The Zz-R genotype showed lesser reduction in all mentioned indices when compared to the Zz-S genotype. The inhibition of photosynthesis under waterlogging occurred due to the reduction in stomatal conductance, fluorescence parameters, and chlorophyll content. Thus, our study revealed that the Zz-R genotype can be a source of genetic diversity for important traits such as morphological and photosynthetic parameters., M. Zhu, F. H. Li, Z. S. Shi., and Obsahuje bibliografii
The recognition of aquatic organisms plays a crucial role in the monitoring of the pollution and for the adoption of rapid preventive actions. A compact microscopic optical imaging system is proposed in order to acquire and treat the multibands fluorescence of several pigments in phytoplankton organisms. Two algorithms for automatic recognition of phytoplankton were proposed with a minimum number of calibration parameters. The first algorithm provides a morphological recognition based on "watershed" segmentation and Fourier descriptors, while the second one builds fluorescence pigment images by "k-means" partition of intensity ratios. The operation of these algorithms was illustrated by the study of two different organisms: a cyanobacteria (Dolichospermum sp.) and an alga (Cladophora sp.). The family and the genus of these organisms were then classified into a database which is independent of the size, the orientation and the position of the specimens in the images., M. Lauffer, F. Genty, S. Margueron, J. L. Collette., and Obsahuje bibliografii
NYB is chlorophyll-less barley mutant, which is controlled by a recessive nuclear gene. The mutation mechanism is revealed. The activities of enzymes transforming 5-aminolevulinic acid into protochlorophyllide were the same in both NYB and the wild type (WT), but the activity of the protochlorophyllide oxidoreductase (POR) in WT was much higher than that of NYB. Most of the photosystem 2 apoproteins were present in both WT and NYB, suggesting that the capability of protein synthesis was probably fully preserved in the mutant. Thus chlorophyll (Chl) biosynthesis in NYB was hampered at conversion form protochlorophyllide (Pchlide) into chlorophyllide. The open reading frame of porB gene in NYB was inserted with a 95 bp fragment, which included a stop codon. The NYB mutant is a very useful material for studies of Chl biosynthesis, chloroplast signalling, and structure of light-harvesting POR-Pchlide complex (LHPP). and Z.-L. Liu ... [et al.].