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Meristematic Cells (meristematic + cell)
Selected AbstractsWhat it takes to get a herbicide's mode of action.PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 5 2005Physionomics, a classical approach in a new complexion Abstract Discovering new herbicides with novel modes of action is a priority assignment in plant protection research. However, for active compounds identified in greenhouse screens, the crucial point is to tread the most efficient path in determining a herbicide's target site, regarding chance of success, time and research costs. Today, in the literature, molecular (functional genomics, transcriptomics), biochemical (proteomics) and analytical (metabolomics) approaches are particularly discussed. So far, less attention has been focused on the comprehensive physiological profiling of the complex plant system as a procedure which enables new herbicides, with an unknown target site for their mode of action, to be screened rapidly. Here, the concept of an array of ,functional' bioassays is presented which has ultimately been developed from the classical tool of mode of action diagnosis by symptoms. These bioassays are designed to differentiate between the distinct responses of the multiple organization units (plant, tissue, meristematic cell, organelle), developmental stages, types of metabolism (phototrophic, heterotrophic) and physiological processes in the plant organism. The response pattern to a herbicide can be viewed as the end result of changes induced in the molecular and biochemical process chain and should be diagnostic of its physiological mode of action. The results can be interpreted directly or a fingerprint database for all known modes of action to be screened for analogy. The term ,physionomics' is proposed for this comprehensive physiological profiling of the plant system, following the parallel terminology of the molecular and biochemical ,omics' technologies. Physionomics procedures provide a first clue to the mode of action of a new herbicide that can direct more time-consuming and costly molecular, biochemical, histochemical or analytical studies to identify a target site more efficiently. Copyright © 2005 Society of Chemical Industry [source] SIZE INCREMENTS DUE TO INTERINDIVIDUAL FUSIONS: HOW MUCH AND FOR HOW LONG?,JOURNAL OF PHYCOLOGY, Issue 4 2010Bernabé Santelices Size increments following interindividual fusions appear as a general benefit for organisms, such as coalescing seaweeds and modular invertebrates, with the capacity to fuse with conspecifics. Using sporelings of the red algae Gracilaria chilensis C. J. Bird, McLachlan et E. C. Oliveira and Mazzaella laminarioides (Bory) Fredericq, we measured the growth patterns of sporelings built with different numbers of spores, and the magnitude and persistence of the size increments gained by fusions. Then we studied three morphological processes that could help explain the observed growth patterns. Results indicate that in these algae, coalescence is followed by immediate increase in total size of the coalesced individual and that the increment is proportional to the number of individuals fusing. However, the size increments in sporelings of both species do not last >60 d. Increasing reductions of marginal meristematic cells and increasing abundance of necrotic cells in sporelings built with increasing numbers of initial spores are partial explanations for the above growth patterns. Since sporelings formed by many spores differentiate erect axes earlier and in larger quantities than sporelings formed by one or only a few spores, differentiation, emergence, and growth of erect axes appear as a more likely explanation for the slow radial growth of the multisporic sporelings. Erect axis differentiation involves significant morphological and physiological changes and a shift from radial to axial growth. It is concluded that the growth pattern exhibited by these macroalgae after fusion differs from equivalent processes described for other organisms with the capacity to fuse, such as modular invertebrates. [source] Molecular physiology of adventitious root formation in Petunia hybrida cuttings: involvement of wound response and primary metabolismNEW PHYTOLOGIST, Issue 3 2009Amir H. Ahkami Summary ,,Adventitious root formation (ARF) in the model plant Petunia hybrida cv. Mitchell has been analysed in terms of anatomy, gene expression, enzymatic activities and levels of metabolites. This study focuses on the involvement of wound response and primary metabolism. ,,Microscopic techniques were complemented with targeted transcript, enzyme and metabolite profiling using real time polymerase chain reaction (PCR), Northern blot, enzymatic assays, chromatography and mass spectrometry. ,,Three days after severance from the stock plants, first meristematic cells appeared which further developed into root primordia and finally adventitious roots. Excision of cuttings led to a fast and transient increase in the wound-hormone jasmonic acid, followed by the expression of jasmonate-regulated genes such as cell wall invertase. Analysis of soluble and insoluble carbohydrates showed a continuous accumulation during ARF. A broad metabolite profiling revealed a strong increase in organic acids and resynthesis of essential amino acids. ,,Substantial changes in enzyme activities and metabolite levels indicate that specific enzymes and metabolites might play a crucial role during ARF. Three metabolic phases could be defined: (i) sink establishment phase characterized by apoplastic unloading of sucrose and being probably mediated by jasmonates; (ii) recovery phase; and (iii) maintenance phase, in which a symplastic unloading occurs. [source] Deposition of Cytokinesis-Related Callose in Riella helicophylla and Arabidopsis thaliana.PLANT BIOLOGY, Issue 4 2001Effects of Photolytically Altered Nifedipine Abstract: The cytokinesis-related callose deposition in cell plates and juvenile cross walls of meristematic cells was investigated in the liverwort Riella helicophylla and seedlings of Arabidopsis thaliana. The ,-1,3-glucan callose was detected by its specific staining properties with sirofluor and aniline blue by fluorescence microscopy. The photo-labile calcium antagonist nifedipine (NIF) exerted a specific promotive effect when the substance was exposed to light. The nitroso derivative of photolysed NIF was found to be the active compound which was responsible for the enhancement in callose deposition. The nitroso derivative was isolated after photolysis of NIF by UV light (365 nm) and its structure was verified with 1H-nuclear magnetic resonance and infrared spectroscopy. The characteristic absorption maximum at 770 nm in dimethyl sulfoxide was employed to determine the concentration of the nitrosopyridine in solutions by use of the molar absorption coefficient of the isolated substance. In addition, the nitro derivative of nifedipine was prepared. This nitropyridine was ineffective with respect to the stimulation of callose deposition in dividing cells. The possible mechanism of this cytotoxic effect and its implications for symplastic growth in meristems is discussed. [source] Re-organisation of the cytoskeleton during developmental programmed cell death in Picea abies embryosTHE PLANT JOURNAL, Issue 5 2003Andrei P. Smertenko Summary Cell and tissue patterning in plant embryo development is well documented. Moreover, it has recently been shown that successful embryogenesis is reliant on programmed cell death (PCD). The cytoskeleton governs cell morphogenesis. However, surprisingly little is known about the role of the cytoskeleton in plant embryogenesis and associated PCD. We have used the gymnosperm, Picea abies, somatic embryogenesis model system to address this question. Formation of the apical,basal embryonic pattern in P. abies proceeds through the establishment of three major cell types: the meristematic cells of the embryonal mass on one pole and the terminally differentiated suspensor cells on the other, separated by the embryonal tube cells. The organisation of microtubules and F-actin changes successively from the embryonal mass towards the distal end of the embryo suspensor. The microtubule arrays appear normal in the embryonal mass cells, but the microtubule network is partially disorganised in the embryonal tube cells and the microtubules disrupted in the suspensor cells. In the same embryos, the microtubule-associated protein, MAP-65, is bound only to organised microtubules. In contrast, in a developmentally arrested cell line, which is incapable of normal embryonic pattern formation, MAP-65 does not bind the cortical microtubules and we suggest that this is a criterion for proembryogenic masses (PEMs) to passage into early embryogeny. In embryos, the organisation of F-actin gradually changes from a fine network in the embryonal mass cells to thick cables in the suspensor cells in which the microtubule network is completely degraded. F-actin de-polymerisation drugs abolish normal embryonic pattern formation and associated PCD in the suspensor, strongly suggesting that the actin network is vital in this PCD pathway. [source] Environmental and auxin regulation of wood formation involves members of the Aux/IAA gene family in hybrid aspenTHE PLANT JOURNAL, Issue 6 2002Richard Moyle Summary Indole acetic acid (IAA/auxin) profoundly affects wood formation but the molecular mechanism of auxin action in this process remains poorly understood. We have cloned cDNAs for eight members of the Aux/IAA gene family from hybrid aspen (Populus tremula L. × Populus tremuloides Michx.) that encode potential mediators of the auxin signal transduction pathway. These genes designated as PttIAA1-PttIAA8 are auxin inducible but differ in their requirement of de novo protein synthesis for auxin induction. The auxin induction of the PttIAA genes is also developmentally controlled as evidenced by the loss of their auxin inducibility during leaf maturation. The PttIAA genes are differentially expressed in the cell types of a developmental gradient comprising the wood-forming tissues. Interestingly, the expression of the PttIAA genes is downregulated during transition of the active cambium into dormancy, a process in which meristematic cells of the cambium lose their sensitivity to auxin. Auxin-regulated developmental reprogramming of wood formation during the induction of tension wood is accompanied by changes in the expression of PttIAA genes. The distinct tissue-specific expression patterns of the auxin inducible PttIAA genes in the cambial region together with the change in expression during dormancy transition and tension wood formation suggest a role for these genes in mediating cambial responses to auxin and xylem development. [source] Cryotherapy of shoot tips: a technique for pathogen eradication to produce healthy planting materials and prepare healthy plant genetic resources for cryopreservationANNALS OF APPLIED BIOLOGY, Issue 3 2009Q.C. Wang Abstract Cryotherapy of shoot tips is a new method for pathogen eradication based on cryopreservation techniques. Cryopreservation refers to the storage of biological samples at ultra-low temperature, usually that of liquid nitrogen (,196°C), and is considered as an ideal means for long-term storage of plant germplasm. In cryotherapy, plant pathogens such as viruses, phytoplasmas and bacteria are eradicated from shoot tips by exposing them briefly to liquid nitrogen. Uneven distribution of viruses and obligate vasculature-limited microbes in shoot tips allows elimination of the infected cells by injuring them with the cryo-treatment and regeneration of healthy shoots from the surviving pathogen-free meristematic cells. Thermotherapy followed by cryotherapy of shoot tips can be used to enhance virus eradication. Cryotherapy of shoot tips is easy to implement. It allows treatment of large numbers of samples and results in a high frequency of pathogen-free regenerants. Difficulties related to excision and regeneration of small meristems are largely circumvented. To date, severe pathogens in banana (Musa spp.), Citrus spp., grapevine (Vitis vinifera), Prunus spp., raspberry (Rubus idaeus), potato (Solanum tuberosum) and sweet potato (Ipomoea batatas) have been eradicated using cryotherapy. These pathogens include nine viruses (banana streak virus, cucumber mosaic virus, grapevine virus A, plum pox virus, potato leaf roll virus, potato virus Y, raspberry bushy dwarf virus, sweet potato feathery mottle virus and sweet potato chlorotic stunt virus), sweet potato little leaf phytoplasma and Huanglongbing bacterium causing ,citrus greening'. Cryopreservation protocols have been developed for a wide variety of plant species, including agricultural and horticultural crops and ornamental plants, and can be used as such or adjusted for the purpose of cryotherapy. [source] | ||||||||||