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1
Clark, S. E., M. P. Running e E. M. Meyerowitz. "CLAVATA3 is a specific regulator of shoot and floral meristem development affecting the same processes as CLAVATA1". Development 121, n. 7 (1 luglio 1995): 2057–67. http://dx.doi.org/10.1242/dev.121.7.2057.
Testo completoAbstract (sommario):
We have previously described the phenotype of Arabidopsis thaliana plants with mutations at the CLAVATA1 (CLV1) locus (Clark, S. E., Running, M. P. and Meyerowitz, E. M. (1993) Development 119, 397–418). Our investigations demonstrated that clv1 plants develop enlarged vegetative and inflorescence apical meristems, and enlarged and indeterminate floral meristems. Here, we present an analysis of mutations at a separate locus, CLAVATA3 (CLV3), that disrupt meristem development in a manner similar to clv1 mutations. clv3 plants develop enlarged apical meristems as early as the mature embryo stage. clv3 floral meristems are also enlarged compared with wild type, and maintain a proliferating meristem throughout flower development. clv3 root meristems are unaffected, indicating that CLV3 is a specific regulator of shoot and floral meristem development. We demonstrate that the strong clv3-2 mutant is largely epistatic to clv1 mutants, and that the semi- dominance of clv1 alleles is enhanced by double heterozygosity with clv3 alleles, suggesting that these genes work in the same pathway to control meristem development. We propose that CLV1 and CLV3 are required to promote the differentiation of cells at the shoot and floral meristem.
2
Laux, T., K. F. Mayer, J. Berger e G. Jurgens. "The WUSCHEL gene is required for shoot and floral meristem integrity in Arabidopsis". Development 122, n. 1 (1 gennaio 1996): 87–96. http://dx.doi.org/10.1242/dev.122.1.87.
Testo completoAbstract (sommario):
Self perpetuation of the shoot meristem is essential for the repetitive initiation of shoot structures during plant development. In Arabidopsis shoot meristem maintenance is disrupted by recessive mutations in the WUSCHEL (WUS) gene. The defect is evident at all developmental stages and is restricted to shoot and floral meristems, whereas the root meristem is not affected. wus mutants fail to properly organize a shoot meristem in the embryo. Postembryonically, defective shoot meristems are initiated repetitively but terminate prematurely in aberrant flat structures. In contrast to wild-type shoot meristems, primordia initiation occurs ectopically across mutant apices, including the center, and often new shoot meristems instead of organs are initiated. The cells of wus shoot apices are larger and more vacuolated than wild-type shoot meristem cells. wus floral meristems terminate prematurely in a central stamen. Double mutant studies indicate that the number of organ primordia in the center of wus flowers is limited, irrespective of organ identity and we propose that meristem cells are allocated into floral whorl domains in a sequential manner. WUS activity also appears to be required for the formation of supernumerary organs in the center of agamous, superman or clavata1 flowers, suggesting that the WUS gene acts upstream of the corresponding genes. Our results suggest that the WUS gene is specifically required for central meristem identity of shoot and floral meristems to maintain their structural and functional integrity.
3
Kang, Huijia, Di Wu, Tianyi Fan e Yan Zhu. "Activities of Chromatin Remodeling Factors and Histone Chaperones and Their Effects in Root Apical Meristem Development". International Journal of Molecular Sciences 21, n. 3 (24 gennaio 2020): 771. http://dx.doi.org/10.3390/ijms21030771.
Testo completoAbstract (sommario):
Eukaryotic genes are packaged into dynamic but stable chromatin structures to deal with transcriptional reprogramming and inheritance during development. Chromatin remodeling factors and histone chaperones are epigenetic factors that target nucleosomes and/or histones to establish and maintain proper chromatin structures during critical physiological processes such as DNA replication and transcriptional modulation. Root apical meristems are vital for plant root development. Regarding the well-characterized transcription factors involved in stem cell proliferation and differentiation, there is increasing evidence of the functional implications of epigenetic regulation in root apical meristem development. In this review, we focus on the activities of chromatin remodeling factors and histone chaperones in the root apical meristems of the model plant species Arabidopsis and rice.
4
Pan, W. H., A. Houben e R. Schlegel. "Highly effective cell synchronization in plant roots by hydroxyurea and amiprophos-methyl or colchicine". Genome 36, n. 2 (1 aprile 1993): 387–90. http://dx.doi.org/10.1139/g93-053.
Testo completoAbstract (sommario):
Effective somatic cell synchronization in root-tip meristems and improved chromosome spreading were achieved in white campion, wheat, rye, and barley by application of hydroxyurea and amiprophos-methyl or colchicine, combined with a pretreatment of ice water and modified fixative, as well as enzymatic digestion of the meristems. The protocol provides metaphase indices of approximately 50%. The chromosomes and chromosomal DNA were with minimum distortion, providing useful material for chromosome banding studies, in situ DNA–DNA hybridization, microdissection, and microcloning.Key words: Melandrium album, rye, wheat, barley, cell cycle, root meristem, synchronization, metaphase index, chromosome preparation.
5
Jackson, D., B. Veit e S. Hake. "Expression of maize KNOTTED1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot". Development 120, n. 2 (1 febbraio 1994): 405–13. http://dx.doi.org/10.1242/dev.120.2.405.
Testo completoAbstract (sommario):
In this paper we describe the expression patterns of a family of homeobox genes in maize and their relationship to organogenic domains in the vegetative shoot apical meristem. These genes are related by sequence to KNOTTED1, a gene characterized by dominant neomorphic mutations which perturb specific aspects of maize leaf development. Four members of this gene family are expressed in shoot meristems and the developing stem, but not in determinate lateral organs such as leaves or floral organs. The genes show distinct expression patterns in the vegetative shoot apical meristem that together predict the site of leaf initiation and the basal limit of the vegetative ‘phytomer’ or segmentation unit of the shoot. These genes are also expressed in the inflorescence and floral meristems, where their patterns of expression are more similar, and they are not expressed in root apical meristems. These findings are discussed in relation to other studies of shoot apical meristem organization as well as possible commonality of homeobox gene function in the animal and plant kingdoms.
6
Du, Yujuan, e Ben Scheres. "PLETHORA transcription factors orchestrate de novo organ patterning during Arabidopsis lateral root outgrowth". Proceedings of the National Academy of Sciences 114, n. 44 (16 ottobre 2017): 11709–14. http://dx.doi.org/10.1073/pnas.1714410114.
Testo completoAbstract (sommario):
Plant development is characterized by repeated initiation of meristems, regions of dividing cells that give rise to new organs. During lateral root (LR) formation, new LR meristems are specified to support the outgrowth of LRs along a new axis. The determination of the sequential events required to form this new growth axis has been hampered by redundant activities of key transcription factors. Here, we characterize the effects of three PLETHORA (PLT) transcription factors, PLT3, PLT5, and PLT7, during LR outgrowth. In plt3plt5plt7 triple mutants, the morphology of lateral root primordia (LRP), the auxin response gradient, and the expression of meristem/tissue identity markers are impaired from the “symmetry-breaking” periclinal cell divisions during the transition between stage I and stage II, wherein cells first acquire different identities in the proximodistal and radial axes. Particularly, PLT1, PLT2, and PLT4 genes that are typically expressed later than PLT3, PLT5, and PLT7 during LR outgrowth are not induced in the mutant primordia, rendering “PLT-null” LRP. Reintroduction of any PLT clade member in the mutant primordia completely restores layer identities at stage II and rescues mutant defects in meristem and tissue establishment. Therefore, all PLT genes can activate the formative cell divisions that lead to de novo meristem establishment and tissue patterning associated with a new growth axis.
7
Haque, MS, e K. Hattori. "Detection of viruses of Bangladeshi and Japanese garlic and their elimination through root meristem culture". Progressive Agriculture 28, n. 2 (9 agosto 2017): 55–63. http://dx.doi.org/10.3329/pa.v28i2.33465.
Testo completoAbstract (sommario):
A number of viruses cause considerable yield loss and quality deterioration in garlic. Root meristems of virus infected plants are known to be free from detectable viruses. This potentiality could be exploited to obtain virus free clones at a high frequency by culturing excised root meristems in vitro. We have developed efficient methods of direct and somatic embryo derived shoot regeneration from root meristems of garlic. The objectives of this work were to detect viruses infecting Bangladeshi and Japanese garlic clones and find an easy and efficient method of eliminating the viruses for the improvement of both yield and quality of garlic. At first, we confirmed the presence of detectable viruses in three Bangladeshi and one Japanese clones. The clones were infected with four different types of viruses: Garlic viruses (GarVs), Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV), and Garlic common latent virus (GCLV). To eliminate those viruses, as per our previous method, root meristems were cultured on MS medium supplemented with 1.0 µM NAA and 10.0 µM BA. Shoot primordia developed from the cultured explants within 1 month. The regenerated individual shoot buds (2-5 mm) were separated from the mother explants and transferred to growth regulators free medium. RT-PCR confirmed that the viruses present in the mother garlic plants were absent in the shoots found after two-step culture. The regenerated shoots were rooted on growth regulator free medium and transferred to pots. Results indicated that the plants remained free from LYSV. Virus elimination through root meristem culture emerged as an efficient novel technique for the eradication of multiple viruses as confirmed by RT-PCR in this study. This technique has the potential for the production and supply of virus free propagules (plants/bulblets) for the yield and quality improvement of garlic.Progressive Agriculture 28 (2): 55-63, 2017
8
Laskowski, M. J., M. E. Williams, H. C. Nusbaum e I. M. Sussex. "Formation of lateral root meristems is a two-stage process". Development 121, n. 10 (1 ottobre 1995): 3303–10. http://dx.doi.org/10.1242/dev.121.10.3303.
Testo completoAbstract (sommario):
In both radish and Arabidopsis, lateral root initiation involves a series of rapid divisions in pericycle cells located on the xylem radius of the root. In Arabidopsis, the number of pericycle cells that divide to form a primordium was estimated to be about 11. To determine the stage at which primordia are able to function as root meristems, primordia of different stages were excised and cultured without added hormones. Under these conditions, primordia that consist of 2 cell layers fail to develop while primordia that consist of at least 3–5 cell layers develop as lateral roots. We hypothesize that meristem formation is a two-step process involving an initial period during which a population of rapidly dividing, approximately isodiametric cells that constitutes the primordium is formed, and a subsequent stage during which meristem organization takes place within the primordium.
9
Stahl, Yvonne, e Rüdiger Simon. "Peptides and receptors controlling root development". Philosophical Transactions of the Royal Society B: Biological Sciences 367, n. 1595 (5 giugno 2012): 1453–60. http://dx.doi.org/10.1098/rstb.2011.0235.
Testo completoAbstract (sommario):
The growth of a plant's root system depends on the continued activity of the root meristem, and the generation of new meristems when lateral roots are initiated. Plants have developed intricate signalling systems that employ secreted peptides and plasma membrane-localized receptor kinases for short- and long-range communication. Studies on growth of the vascular system, the generation of lateral roots, the control of cell differentiation in the root meristem and the interaction with invading pathogens or symbionts has unravelled a network of peptides and receptor systems with occasionally shared functions. A common theme is the employment of conserved modules, consisting of a short signalling peptide, a receptor-like kinase and a target transcription factor, that control the fate and proliferation of stem cells during root development. This review intends to give an overview of the recent advances in receptor and peptide ligand-mediated signalling involved in root development.
10
Sato, Moeko, Hiroko Akashi, Yuki Sakamoto, Sachihiro Matsunaga e Hiroyuki Tsuji. "Whole-Tissue Three-Dimensional Imaging of Rice at Single-Cell Resolution". International Journal of Molecular Sciences 23, n. 1 (21 dicembre 2021): 40. http://dx.doi.org/10.3390/ijms23010040.
Testo completoAbstract (sommario):
The three-dimensional (3D) arrangement of cells in tissues provides an anatomical basis for analyzing physiological and biochemical aspects of plant and animal cellular development and function. In this study, we established a protocol for tissue clearing and 3D imaging in rice. Our protocol is based on three improvements: clearing with iTOMEI (clearing solution suitable for plants), developing microscopic conditions in which the Z step is optimized for 3D reconstruction, and optimizing cell-wall staining. Our protocol successfully 3D imaged rice shoot apical meristems, florets, and root apical meristems at cellular resolution throughout whole tissues. Using fluorescent reporters of auxin signaling in rice root tips, we also revealed the 3D distribution of auxin signaling events that are activated in the columella, quiescent center, and multiple rows of cells in the stele of the root apical meristem. Examination of cells with higher levels of auxin signaling revealed that only the central row of cells was connected to the quiescent center. Our method provides opportunities to observe the 3D arrangement of cells in rice tissues.
11
Chiatante, Donato, Lucia Maiuro e Gabriella S. Scippa. "Water Stress Tolerance in Root Meristems". Giornale botanico italiano 128, n. 1 (gennaio 1994): 151. http://dx.doi.org/10.1080/11263509409437044.
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12
Chiatante, D., L. Maiuro e G. S. Scippa. "Water Stress Tolerance in Root Meristems". Giornale botanico italiano 130, n. 1 (gennaio 1996): 392. http://dx.doi.org/10.1080/11263509609439627.
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13
Carrillo-Flores, Elizabeth, Denni Mariana Pazos-Solis, Frida Paola Diaz-Bellacetin, Grisel Fierros-Romero, Elda Beltran-Pena e Maria Elena Mellado-Rojas. "TOR regulates plant development and plantmicroorganism interactions". Journal of Applied Biotechnology & Bioengineering 8, n. 3 (7 maggio 2021): 68–74. http://dx.doi.org/10.15406/jabb.2021.08.00255.
Testo completoAbstract (sommario):
The adaptation of plants to their ever-changing environment denotes a remarkable plasticity of growth that generates organs throughout their life cycle, by the activation of a group of pluripotent cells known as shoot apical meristem and root apical meristem. The reactivation of cellular proliferation in both meristems by means of TOR, Target Of Rapamycin, depends on specific signals such as glucose and light. TOR showed a significant influence in plant growth, development and nutrient assimilation as well as in microorganism interactions such as infection resistance, plant differentiation and root node symbiosis. This review highlights the pathways and effects of TOR in the sensing of environmental signals throughout the maturing of different plant species
14
Chiatante, Donato, Antonio Montagnoli, Dalila Trupiano, Gabriella Sferra, John Bryant, Thomas L. Rost e Gabriella S. Scippa. "Meristematic Connectome: A Cellular Coordinator of Plant Responses to Environmental Signals?" Cells 10, n. 10 (26 settembre 2021): 2544. http://dx.doi.org/10.3390/cells10102544.
Testo completoAbstract (sommario):
Mechanical stress in tree roots induces the production of reaction wood (RW) and the formation of new branch roots, both functioning to avoid anchorage failure and limb damage. The vascular cambium (VC) is the factor responsible for the onset of these responses as shown by their occurrence when all primary tissues and the root tips are removed. The data presented confirm that the VC is able to evaluate both the direction and magnitude of the mechanical forces experienced before coordinating the most fitting responses along the root axis whenever and wherever these are necessary. The coordination of these responses requires intense crosstalk between meristematic cells of the VC which may be very distant from the place where the mechanical stress is first detected. Signaling could be facilitated through plasmodesmata between meristematic cells. The mechanism of RW production also seems to be well conserved in the stem and this fact suggests that the VC could behave as a single structure spread along the plant body axis as a means to control the relationship between the plant and its environment. The observation that there are numerous morphological and functional similarities between different meristems and that some important regulatory mechanisms of meristem activity, such as homeostasis, are common to several meristems, supports the hypothesis that not only the VC but all apical, primary and secondary meristems present in the plant body behave as a single interconnected structure. We propose to name this structure “meristematic connectome” given the possibility that the sequence of meristems from root apex to shoot apex could represent a pluricellular network that facilitates long-distance signaling in the plant body. The possibility that the “meristematic connectome” could act as a single structure active in adjusting the plant body to its surrounding environment throughout the life of a plant is now proposed.
15
Flessner, Michael L., Roland R. Dute e J. Scott McElroy. "Anatomical Response of St. Augustinegrass to Aminocyclopyrachlor Treatment". Weed Science 59, n. 2 (giugno 2011): 263–69. http://dx.doi.org/10.1614/ws-d-10-00116.1.
Testo completoAbstract (sommario):
Aminocyclopyrachlor (AMCP) is a synthetic auxin herbicide that controls primarily broadleaf (eudicotyledonous) weeds. Previous research indicates that St. Augustinegrass is unacceptably injured by AMCP. In light of the fact that synthetic auxin herbicides usually are safe when applied to monocotyledons, the mechanism for this injury is not fully understood. Anatomical response of St. Augustinegrass to AMCP was investigated using light microscopy. Apical meristem node tissue responded with callus tissue proliferation, abnormal location and development of the apical meristem, necrosis of the developing vascular tissue, vascular parenchyma proliferation, and xylem gum blockages. Node tissues away from the apical meristem responded with xylem gum blockages and the stimulation of lateral meristems and adventitious root formation. Root tip response to AMCP treatment was characterized by a loss of organization. Root tip apical meristem and vascular tissue maturation was disorganized. Additionally, lateral root generation occurred abnormally close to the root tip. These responses impair affected tissue functionality. Mature tissue was unaffected by AMCP treatment. All of these responses are characteristic of synthetic auxin herbicide treatment to other susceptible species. This research indicates that AMCP treatment results in St. Augustinegrass injury and subsequent death through deleterious growth stimulation and concomitant vascular inhibition.
16
Cheng, Shan, Qi Wang, Hakim Manghwar e Fen Liu. "Autophagy-Mediated Regulation of Different Meristems in Plants". International Journal of Molecular Sciences 23, n. 11 (2 giugno 2022): 6236. http://dx.doi.org/10.3390/ijms23116236.
Testo completoAbstract (sommario):
Autophagy is a highly conserved cell degradation process that widely exists in eukaryotic cells. In plants, autophagy helps maintain cellular homeostasis by degrading and recovering intracellular substances through strict regulatory pathways, thus helping plants respond to a variety of developmental and environmental signals. Autophagy is involved in plant growth and development, including leaf starch degradation, senescence, anthers development, regulation of lipid metabolism, and maintenance of peroxisome mass. More and more studies have shown that autophagy plays a role in stress response and contributes to maintain plant survival. The meristem is the basis for the formation and development of new tissues and organs during the post-embryonic development of plants. The differentiation process of meristems is an extremely complex process, involving a large number of morphological and structural changes, environmental factors, endogenous hormones, and molecular regulatory mechanisms. Recent studies have demonstrated that autophagy relates to meristem development, affecting plant growth and development under stress conditions, especially in shoot and root apical meristem. Here, we provide an overview of the current knowledge about how autophagy regulates different meristems under different stress conditions and possibly provide new insights for future research.
17
Fernandez, D. E., F. R. Turner e M. L. Crouch. "In situ localization of storage protein mRNAs in developing meristems of Brassica napus embryos". Development 111, n. 2 (1 febbraio 1991): 299–313. http://dx.doi.org/10.1242/dev.111.2.299.
Testo completoAbstract (sommario):
Probes derived from cDNA clones of napin and cruciferin, the major storage proteins of Brassica napus, and in situ hybridization techniques were used to examine changes in the spatial and temporal distribution of storage protein messages during the course of embryogeny, with a special emphasis on the developing apical meristems. Napin mRNAs begin to accumulate in the cortex of the axis during late heart stage, in the outer faces of the cotyledons during torpedo stage and in the inner faces of the cotyledons during cotyledon stage. Cruciferin mRNAs accumulate in a similar pattern but approximately 5 days later. Cells in the apical regions where root and shoot meristems develop do not accumulate storage protein messages during early stages of embryogeny. In the upper axis, the boundary between these apical cells and immediately adjacent cells that accumulate napin and cruciferin mRNAs is particularly distinct. Our analysis indicates that this boundary is not related to differences in tissue or cell type, but appears instead to be coincident with the site of a particular set of early cell divisions. A major change in the mRNA accumulation patterns occurs halfway through embryogeny, as the embryos enter maturation stage and start drying down. Final maturation of the shoot apical meristem is associated with the development of leaf primordia and the accumulation of napin mRNAs in the meristem, associated leaf primordia and vascular tissue. Cruciferin mRNAs accumulate only in certain zones of the shoot apical meristem and on the flanks of leaf primordia. Neither type of mRNA accumulates in the root apical meristem at any stage.
18
Miwa, Hiroki, Atsuko Kinoshita, Hiroo Fukuda e Shinichiro Sawa. "Plant meristems: CLAVATA3/ESR-related signaling in the shoot apical meristem and the root apical meristem". Journal of Plant Research 122, n. 1 (23 dicembre 2008): 31–39. http://dx.doi.org/10.1007/s10265-008-0207-3.
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19
Wendrich, Jos R., Barbara K. Möller, Song Li, Shunsuke Saiga, Rosangela Sozzani, Philip N. Benfey, Bert De Rybel e Dolf Weijers. "Framework for gradual progression of cell ontogeny in the Arabidopsis root meristem". Proceedings of the National Academy of Sciences 114, n. 42 (2 ottobre 2017): E8922—E8929. http://dx.doi.org/10.1073/pnas.1707400114.
Testo completoAbstract (sommario):
In plants, apical meristems allow continuous growth along the body axis. Within the root apical meristem, a group of slowly dividing quiescent center cells is thought to limit stem cell activity to directly neighboring cells, thus endowing them with unique properties, distinct from displaced daughters. This binary identity of the stem cells stands in apparent contradiction to the more gradual changes in cell division potential and differentiation that occur as cells move further away from the quiescent center. To address this paradox and to infer molecular organization of the root meristem, we used a whole-genome approach to determine dominant transcriptional patterns along root ontogeny zones. We found that the prevalent patterns are expressed in two opposing gradients. One is characterized by genes associated with development, the other enriched in differentiation genes. We confirmed these transcript gradients, and demonstrate that these translate to gradients in protein accumulation and gradual changes in cellular properties. We also show that gradients are genetically controlled through multiple pathways. Based on these findings, we propose that cells in the Arabidopsis root meristem gradually transition from stem cell activity toward differentiation.
20
Chapman, Elisabeth J., e Mark Estelle. "Cytokinin and auxin intersection in root meristems". Genome Biology 10, n. 2 (2009): 210. http://dx.doi.org/10.1186/gb-2009-10-2-210.
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21
CLOWES, F. A. L. "Origin of the epidermis in root meristems". New Phytologist 127, n. 2 (giugno 1994): 335–47. http://dx.doi.org/10.1111/j.1469-8137.1994.tb04284.x.
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22
Dolan, Liam. "Meristems: The Root of Stem Cell Regulation". Current Biology 19, n. 11 (giugno 2009): R459—R460. http://dx.doi.org/10.1016/j.cub.2009.04.030.
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23
Lasok, Hanna, Hugues Nziengui, Philip Kochersperger e Franck Anicet Ditengou. "Arabidopsis Root Development Regulation by the Endogenous Folate Precursor, Para-Aminobenzoic Acid, via Modulation of the Root Cell Cycle". Plants 12, n. 24 (5 dicembre 2023): 4076. http://dx.doi.org/10.3390/plants12244076.
Testo completoAbstract (sommario):
The continuous growth of roots depends on their ability to maintain a balanced ratio between cell production and cell differentiation at the tip. This process is regulated by the hormonal balance of cytokinin and auxin. However, other important regulators, such as plant folates, also play a regulatory role. In this study, we investigated the impact of the folate precursor para-aminobenzoic acid (PABA) on root development. Using pharmacological, genetic, and imaging approaches, we show that the growth of Arabidopsis thaliana roots is repressed by either supplementing the growth medium with PABA or overexpressing the PABA synthesis gene GAT-ADCS. This is associated with a smaller root meristem consisting of fewer cells. Conversely, reducing the levels of free root endogenous PABA results in longer roots with extended meristems. We provide evidence that PABA represses Arabidopsis root growth in a folate-independent manner and likely acts through two mechanisms: (i) the G2/M transition of cell division in the root apical meristem and (ii) promoting premature cell differentiation in the transition zone. These data collectively suggest that PABA plays a role in Arabidopsis root growth at the intersection between cell division and cell differentiation.
24
Mikou, Karima, e Philippe Badila. "Induction photopériodique de l'organogenèse et de la floraison in vitro chez le Cichorium intybus: aspects histologiques". Canadian Journal of Botany 70, n. 6 (1 giugno 1992): 1302–11. http://dx.doi.org/10.1139/b92-163.
Testo completoAbstract (sommario):
In root explants of a long-day plant, Cichorium intybus L., grown in vitro, inflorescences were produced under short-day conditions (9 h) if long days were applied on days 10 to 18 of culture. Long days consisted of either 16 h fluorescent light (5.6 W∙m−2) or daily cycles of 9 h white fluorescent plus 15 h red (660 nm, 0.3 W∙m−2) or blue (440 nm, 0.5 W∙m−2) light. The structural changes in the meristems of buds regenerated under these conditions were studied. The influence of photoperiod appeared to be critical between the 10th and 16th days, during the progressive transition from vegetative to prefloral stage, which occurred more rapidly under photoperiodic conditions with red or blue light. In noninductive short days, intermediate meristems could be observed tardily on day 24, but no flower formation took place after transfer to long days. Increasing the quantity of light under short-day conditions up to a level comparable to long-day conditions resulted in a rise in mitotic activity, mainly in the peripheral zone of the meristem, but the vegetative zonation was retained. These data therefore indicate that the duration of light really commits the meristem to the subsequent formation of flower primordia; in contrast, the quantity of light controls the bud formation during the first part of development. Key words: Cichorium, tissue cultures, flowering, meristems, organogenesis, photoperiodism.
25
Martin, George C. "Apical Dominance". HortScience 22, n. 5 (ottobre 1987): 824–33. http://dx.doi.org/10.21273/hortsci.22.5.824.
Testo completoAbstract (sommario):
Abstract None of the physiological events in plant growth and development is truly independent. Photosynthesis, flowering, and mineral transport are sharply focused areas of research; yet these phenomena are not separable from other metabolic events in the plant. This feature of interdependence may be called correlations (26) or growth correlations (49, 50). The control exerted by the growth zone emanates from a meristem; these meristems include the root or shoot apex, cambium, flowers, fruit, pollen on stigma, and the ovule or seed in a fruit.
26
Sherman, D., e J. Banks. "Ceratopteris is a Useful Model Genetic System for Studying Plant Meristem Development." Microscopy and Microanalysis 3, S2 (agosto 1997): 107–8. http://dx.doi.org/10.1017/s143192760000742x.
Testo completoAbstract (sommario):
Most tissues of a plant are derived from meristems that reside at the tips of the shoot and root. To identify genes that are involved in the organization and in the coordination of cell division and differentation in the meristem, mutations that affect meristem development have been sought. Several mutations that affect meristem development have been characterized in Arabidopsis and maize; however, the angiosperm meristem is small, inconspicuous and difficult to characterize in a non-destructive way. Gametophytes of the fern Ceratopteris richardii have a meristem that is simple, small and conspicuous and is an ideal system for studying meristem development. In this study, the meristems of wild-type and various mutant gametophytes of Ceratopteris are described using cold stage SEM of hydrated gametophytes.The haploid gametophytes of the fern Ceratopteris are either male or hermaphroditic and are easily distinguished by size and shape as well as by type of sex organ produced. Hermaphrodites form a distinct meristem; newly divided cells of this meristem have only four possible cells fates: they may differentiate as antheridia, the sperm-forming organs; differentiate as archegonia, the egg-forming organs; enlarge to contribute to the growing two-dimensional sheet of cells; or remain within to maintain the meristem (Fig. 1; an=antheridia; ar=archegonia). Male gametophytes lack a meristem and are thus much smaller than hermphrodites. Almost all cells of the male differentiate as antheridia, the sperm-forming organs (Fig. 2). Because the gametophytes of Ceratopteris are small (<3 mm), conspicious, free-living, and haploid, it is very simple to select mutations that affect the sex of the gametophyte as well the meristem.
27
Benbadis, M. C., M. Delage e G. Daouse. "Effet stimulant de la poly-D-lysine sur l'entrée en mitose de cellules G2 du méristème racinaire d'Allium sativum". Canadian Journal of Botany 63, n. 1 (1 gennaio 1985): 155–62. http://dx.doi.org/10.1139/b85-018.
Testo completoAbstract (sommario):
Cell proliferation in Allium sativum L. primary root meristems is stimulated by poly-D-lysine. This effect has been studied on asynchronous and on hydroxyurea-synchronized meristems using cell kinetics techniques and DNA microdensitometry. The rapid increase of mitotic indices is the result of the onset of mitosis in 4C cells which are arrested in G2. However, neither the initiation of DNA synthesis in G1 cells, nor the labelling index of roots continuously incubated with tritiated thymidine, are altered. Thus, poly-D-lysine has a selective effect on G2 cells, triggering the onset of mitosis in those cells. Our results, which show that mitosis can be induced in G2 cells by an exogenous supply of a polycationic compound, are discussed in relation to the occurrence and the features of G2-arrested cells within root meristems.
28
Silva, Thaís Cristina Ribeiro, Isabella Santiago Abreu e Carlos Roberto Carvalho. "Improved and Reproducible Flow Cytometry Methodology for Nuclei Isolation from Single Root Meristem". Journal of Botany 2010 (22 giugno 2010): 1–7. http://dx.doi.org/10.1155/2010/320609.
Testo completoAbstract (sommario):
Root meristems have increasingly been target of cell cycle studies by flow cytometric DNA content quantification. Moreover, roots can be an alternative source of nuclear suspension when leaves become unfeasible and for chromosome analysis and sorting. In the present paper, a protocol for intact nuclei isolation from a single root meristem was developed. This proceeding was based on excision of the meristematic region using a prototypical slide, followed by short enzymatic digestion and mechanical isolation of nuclei during homogenization with a hand mixer. Such parameters were optimized for reaching better results. Satisfactory nuclei amounts were extracted and analyzed by flow cytometry, producing histograms with reduced background noise and CVs between 3.2 and 4.1%. This improved and reproducible technique was shown to be rapid, inexpensive, and simple for nuclear extraction from a single root tip, and can be adapted for other plants and purposes.
29
Nascimento, Heloisa Rocha do, Ricardo Gallo, Isane Vera Karsburg e Ademilso Sampaio Oliveira. "Cytogenetic and identification of the nucleolus organizer region in Heliconia bihai (L.) L." Revista Ceres 61, n. 4 (agosto 2014): 451–57. http://dx.doi.org/10.1590/0034-737x201461040002.
Testo completoAbstract (sommario):
The genus Heliconia is not much studied and the number of existing species in this genus is still uncertain. It is known that this number relies between 150 to 250 species. In Brazil, about 40 species are native and known by many different names. The objective of this paper was to characterize morphometrically and to identify the NOR (active nucleolus organizer regions) by Ag-NOR banding of chromosomes of Heliconia bihai (L) L. Root meristems were submitted to blocking treatment in an amiprofos-methyl (APM) solution, fixed in methanol-acetic acid solution for 24 hours, at least. The meristems were washed in distilled water and submitted to enzymatic digestion with pectinase enzyme. The slides were prepared by dissociation of the root meristem, dried in the air and also on hot plate at 50°C. Subsequently, some slides were submitted to 5% Giemsa stain for karyotype construction and to a solution of silver nitrate (AgNO3) 50% for Ag-NOR banding. The species H. bihai has 2n = 22 chromosomes, 4 pairs of submetacentric chromosomes and 7 pairs of metacentric chromosomes, and graded medium to short (3.96 to 0.67 μM), with the presence of active NOR in pairs 1 and 2 and interphase cells with 2 nucleoli. These are the features of a diploid species.
30
Robertson, E. J., K. A. Pyke e R. M. Leech. "arc6, an extreme chloroplast division mutant of Arabidopsis also alters proplastid proliferation and morphology in shoot and root apices". Journal of Cell Science 108, n. 9 (1 settembre 1995): 2937–44. http://dx.doi.org/10.1242/jcs.108.9.2937.
Testo completoAbstract (sommario):
The arc6 (accumulation and replication of chloroplasts) mutant of Arabidopsis has only two greatly enlarged chloroplasts per mature leaf mesophyll cell compared with ninety chloroplasts per cell in the wild type. The mutation is a single nuclear gene and the plant phenotype is normal. Shoot and root apical meristems of arc6 plants have been examined to determine how early during plastid development the mutant arc6 phenotype can be recognised. In the cells of the arc6 apical meristem there are only two proplastids, which are larger than wild type with a highly variable morphology. In the cells of the leaf primordia where differentiation of proplastids to chloroplasts occurs arc6 plastids are larger and at a more advanced developmental stage than wild-type plastids. In arc6 root cells statoliths and other plastids also show grossly abnormal morphology and the statoliths are greatly increased in size. During arc6 stomatal guard cell development the perturbation in proplastid population dynamics affects plastid segregation and 30% of stomata lack plastids in one or both guard cells. Our evidence would suggest that ARC6 is expressed throughout the vegetative cells of the Arabidopsis seedling with major effects on both the proplastid phenotype and the proplastid population. ARC6 is the first gene to be identified in Arabidopsis which has a global effect on plastid development in cells arising from both the shoot and root meristems, and is of major importance in the nuclear control of plastid differentiation in higher plants.
31
Rowland, R. E. "Nucleolus DNA synthesis inVicia faba root-tip meristems". Experientia 41, n. 8 (agosto 1985): 1070–72. http://dx.doi.org/10.1007/bf01952149.
Testo completo
32
Krauss, Ulrike. "Detached Leaf Technique for the Establishment of Root Cultures of Peanut (Arachis hypogaea L.)". Peanut Science 22, n. 2 (1 luglio 1995): 81–84. http://dx.doi.org/10.3146/i0095-3679-22-2-1.
Testo completoAbstract (sommario):
Abstract Axenic cultures of peanut (Arachis hypogaea L.) roots can be initiated from in vitro cultured embryos and shoot meristems. Embryo axes produced more shoots than tissue taken from axillary meristems. For tissue derived from shoot cultures, Virginia cultivars had a higher percentage of rooting explants than a Spanish cultivar. Inoculation with Agrobacterium rhizogenes increased root yields. However, root propagation in liquid medium was unsuccessful. On the other hand, the use of detached leaves, incubated on a sand/mineral liquid medium, led to vigorous root production after inoculation with A. rhizogenes, regardless of the bacterial strain used. These roots could be propagated subsequently in liquid medium. The advantages of the detached leaf technique are discussed.
33
Schneider, Michael, Lucia Vedder, Benedict Chijioke Oyiga, Boby Mathew, Heiko Schoof, Jens Léon e Ali Ahmad Naz. "Transcriptome profiling of barley and tomato shoot and root meristems unravels physiological variations underlying photoperiodic sensitivity". PLOS ONE 17, n. 9 (12 settembre 2022): e0265981. http://dx.doi.org/10.1371/journal.pone.0265981.
Testo completoAbstract (sommario):
The average sowing date of crops in temperate climate zones has been shifted forwards by several days, resulting in a changed photoperiod regime at the emergence stage. In the present study, we performed a global transcriptome profiling of plant development genes in the seedling stage of root and shoot apical meristems of a photoperiod-sensitive species (barley) and a photoperiod insensitive species (tomato) in short-day conditions (8h). Variant expression indicated differences in physiological development under this short day-length regime between species and tissues. The barley tissue transcriptome revealed reduced differentiation compared to tomato. In addition, decreased photosynthetic activity was observed in barley transcriptome and leaf chlorophyll content under 8h conditions, indicating a slower physiological development of shoot meristems than in tomatoes. The photomorphogenesis controlling cryptochrome gene cry1, with an effect on physiological differentiation, showed an underexpression in barley compared to tomato shoot meristems. This might lead to a cascade of suspended sink-source activities, which ultimately delay organ development and differentiation in barley shoot meristems under short photoperiods.
34
Podbielkowska, Maria. "Effect of methotrexate on the ultrastructure of Alliurn ceps L. and Haemanthus albiflos Jacq. roots cultured under anaerobic conditions". Acta Societatis Botanicorum Poloniae 50, n. 4 (2014): 557–61. http://dx.doi.org/10.5586/asbp.1981.075.
Testo completoAbstract (sommario):
Changes were found in the cell structure of the root meristems of <em>Haemanthus albiflos</em> and <em>Allium cepa</em> treated with methotrexate, an oncostatic preparation of the antimetabolite group. Root culture was conducted under anaerorbic conditions to induce In this way glycolysis typical for neoplastic cells. In <em>Haemanthus</em>, where the glycolytilc process runs normally, hypertrophy of the rough ER membranes noted correlated with the presence of numerous mitochondria and dictyasames with changed Structure. In <em>Allium</em> cells, where the glycalytic process runs with the participation of alliin, methotrexate did not evoke development of ER membranes. The structure of mitochondria and dictyosomes was similar as that in the root meristem of <em>Haemanthus</em>. In both studied objects thickening of the cell wall was noted.
35
Kitagawa, Munenori, e David Jackson. "Control of Meristem Size". Annual Review of Plant Biology 70, n. 1 (29 aprile 2019): 269–91. http://dx.doi.org/10.1146/annurev-arplant-042817-040549.
Testo completoAbstract (sommario):
A fascinating feature of plant growth and development is that plants initiate organs continually throughout their lifespan. The ability to do this relies on specialized groups of pluripotent stem cells termed meristems, which allow for the elaboration of the shoot, root, and vascular systems. We now have a deep understanding of the genetic networks that control meristem initiation and stem cell maintenance, including the roles of receptors and their ligands, transcription factors, and integrated hormonal and chromatin control. This review describes these networks and discusses how this knowledge is being applied to improve crop productivity by increasing fruit size and seed number.
36
Anderson, J. A., C. Mousset-Déclas, E. G. Williams e N. L. Taylor. "An in vitro chromosome doubling method for clovers (Trifolium spp.)". Genome 34, n. 1 (1 febbraio 1991): 1–5. http://dx.doi.org/10.1139/g91-001.
Testo completoAbstract (sommario):
This research reports a new technique for chromosome doubling of clover (Trifolium sp.) axillary meristems via in vitro colchicine application. Plant material utilized included T. pratense (red clover) cv. Kenstar clones, and three interspecific hybrids: T. ambiguum (kura clover) × T. repens (white clover); T. alpestre × T. pratense; and T. sarosiense × T. pratense. Vegetative axillary meristems were excised from plants, surface sterilized, and trimmed to a length of 0.5–1 mm. Meristems were placed on the surface of a shoot proliferation medium (ML8) containing colchicine (0.1%) for 48 or 72 h and then transferred back to ML8. Alternative treatments were to preculture meristems on ML8 for 7 days prior to colchicine treatment. Plantlets with two or three trifoliolate leaves were induced to root on CR2 or RL rooting media. Preculturing of meristems on ML8 prior to colchicine exposure resulted in the highest chromosome doubling frequencies among the different genotypes, although there was apparent genotype × treatment interaction. Chromosome doubling frequencies were as high as 81 and 44% for initial root tips and mature shoots, respectively. To make rapid assessments of ploidy level of flowering plants, pollen shape was examined. Chromosome doubling increased the pollen stainability of the T. ambiguum × T. repens hybrid from 2.5 to 33.6%, but did not result in fertility in the other two interspecific hybrids.Key words: Trifolium, colchicine, chromosome doubling, interspecific hybrids.
37
Li, Huchen, Stefan Schilderink, Qingqin Cao, Olga Kulikova e Ton Bisseling. "Plant-specific histone deacetylases are essential for early and late stages of Medicago nodule development". Plant Physiology 186, n. 3 (21 marzo 2021): 1591–605. http://dx.doi.org/10.1093/plphys/kiab140.
Testo completoAbstract (sommario):
Abstract Legume and rhizobium species can establish a nitrogen-fixing nodule symbiosis. Previous studies have shown that several transcription factors that play a role in (lateral) root development are also involved in nodule development. Chromatin remodeling factors, like transcription factors, are key players in regulating gene expression. However, studies have not investigated whether chromatin remodeling genes that are essential for root development are also involved in nodule development. Here, we studied the role of Medicago (Medicago truncatula) histone deacetylases (MtHDTs) in nodule development. Arabidopsis (Arabidopsis thaliana) orthologs of HDTs have been shown to play a role in root development. MtHDT expression is induced in nodule primordia and is maintained in the nodule meristem and infection zone. Conditional, nodule-specific knockdown of MtHDT expression by RNAi blocks nodule primordium development. A few nodules may still form, but their nodule meristems are smaller, and rhizobial colonization of the cells derived from the meristem is markedly reduced. Although the HDTs are expressed during nodule and root development, transcriptome analyses indicate that HDTs control the development of each organ in a different manner. During nodule development, the MtHDTs positively regulate 3-hydroxy-3-methylglutaryl coenzyme a reductase 1 (MtHMGR1). Decreased expression of MtHMGR1 is sufficient to explain the inhibition of primordium formation.
38
Ruiz-Medrano, R., B. Xoconostle-Cazares e W. J. Lucas. "Phloem long-distance transport of CmNACP mRNA: implications for supracellular regulation in plants". Development 126, n. 20 (15 ottobre 1999): 4405–19. http://dx.doi.org/10.1242/dev.126.20.4405.
Testo completoAbstract (sommario):
Direct support for the concept that RNA molecules circulate throughout the plant, via the phloem, is provided through the characterisation of mRNA from phloem sap of mature pumpkin (Cucurbita maxima) leaves and stems. One of these mRNAs, CmNACP, is a member of the NAC domain gene family, some of whose members have been shown to be involved in apical meristem development. In situ RT-PCR analysis revealed the presence of CmNACP RNA in the companion cell-sieve element complex of leaf, stem and root phloem. Longitudinal and transverse sections showed continuity of transcript distribution between meristems and sieve elements of the protophloem, suggesting CmNACP mRNA transport over long distances and accumulation in vegetative, root and floral meristems. In situ hybridization studies conducted on CmNACP confirmed the results obtained using in situ RT-PCR. Phloem transport of CmNACP mRNA was proved directly by heterograft studies between pumpkin and cucumber plants, in which CmNACP transcripts were shown to accumulate in cucumber scion phloem and apical tissues. Similar experiments were conducted with 7 additional phloem-related transcripts. Collectively, these studies established the existence of a system for the delivery of specific mRNA transcripts from the body of the plant to the shoot apex. These findings provide insight into the presence of a novel mechanism likely used by higher plants to integrate developmental and physiological processes on a whole-plant basis.
39
Kaszler, Nikolett, Péter Benkő, Dóra Bernula, Ágnes Szepesi, Attila Fehér e Katalin Gémes. "Polyamine Metabolism Is Involved in the Direct Regeneration of Shoots from Arabidopsis Lateral Root Primordia". Plants 10, n. 2 (5 febbraio 2021): 305. http://dx.doi.org/10.3390/plants10020305.
Testo completoAbstract (sommario):
Plants can be regenerated from various explants/tissues via de novo shoot meristem formation. Most of these regeneration pathways are indirect and involve callus formation. Besides plant hormones, the role of polyamines (PAs) has been implicated in these processes. Interestingly, the lateral root primordia (LRPs) of Arabidopsis can be directly converted to shoot meristems by exogenous cytokinin application. In this system, no callus formation takes place. We report that the level of PAs, especially that of spermidine (Spd), increased during meristem conversion and the application of exogenous Spd improved its efficiency. The high endogenous Spd level could be due to enhanced synthesis as indicated by the augmented relative expression of PA synthesis genes (AtADC1,2, AtSAMDC2,4, AtSPDS1,2) during the process. However, the effect of PAs on shoot meristem formation might also be dependent on their catabolism. The expression of Arabidopsis POLYAMINE OXIDASE 5 (AtPAO5) was shown to be specifically high during the process and its ectopic overexpression increased the LRP-to-shoot conversion efficiency. This was correlated with Spd accumulation in the roots and ROS accumulation in the converting LRPs. The potential ways how PAO5 may influence direct shoot organogenesis from Arabidopsis LRPs are discussed.
40
Yeung, Edward C., Claudio Stasolla e Lisheng Kong. "Apical meristem formation during zygotic embryo development of white spruce". Canadian Journal of Botany 76, n. 5 (1 maggio 1998): 751–61. http://dx.doi.org/10.1139/b98-042.
Testo completoAbstract (sommario):
The first notable sign of shoot and root meristem development in zygotic embryos of white spruce (Picea glauca (Moench) Voss) was the appearance of starch in the respective poles of the embryo. Starch granules gradually accumulated in the subapical cells of the shoot pole and were soon followed by vacuolation in the subapical cells. Vacuolation reached its highest degree in these cells at the early embryo stage. With the formation of the large vacuolated cells, the surface cell layer at the summit of the shoot pole enlarged and differentiated into the surface initials of the shoot meristem. These cells were large with distinct nuclei. As the embryo matured, the large vacuoles within the subapical cells were replaced by small ones with a concomitant increase in the cytoplasmic density of the subapical cells. After germination, the surface initials remained distinct; however, the subapical cells had different fates depending on their location. The subapical cells located next to the surface initials became the central mother cells of the shoot meristem and those located near the cotyledon junction divided periclinally and gave rise to the epicotyl rib meristem. The remaining subapical cells near the procambium became part of the pith. In the root pole, starch could be found in the cap region terminating underneath the developing procambium at the club-shaped stage of embryo development. Two layers of root initials appeared at the junction between the developing procambium and the root cap. The initials were distinct as they were larger in size than surrounding cells. Cell division activity could not be detected in the layer of initials immediately next to the procambium, while mitotic activity could be seen in the adjoining layer next to the root cap. As the embryo matured, cells surrounding the root initials also took on structural characteristics similar to the root meristem initials. As a result, the region of the root meristem initials expanded in size, and the bilayered configuration became obscure. After germination, mitotic figures could be found in the root initials. As seedling continued to grow, fewer mitotic figures could be found in the root meristem cells adjacent to the procambium pole. In roots of mature plants, a group of isodiametric cells could be discerned between the procambium and the root cap. Mitotic activity was not readily detected within this group of isodiametric cells but mitotic figures could be found in surrounding cells.Key words: apical meristems, Picea glauca, white spruce, zygotic embryogenesis.
41
Lemon, Gordon D., e Usher Posluszny. "A new approach to the study of apical meristem development using laser scanning confocal microscopy". Canadian Journal of Botany 76, n. 5 (1 maggio 1998): 899–904. http://dx.doi.org/10.1139/b98-043.
Testo completoAbstract (sommario):
Epi-illumination light microscopy and scanning electron microscopy have been standard techniques for developmental studies of shoot apices. Recently, laser scanning confocal microscopy has gained popularity as a tool for biological imaging. We have adapted laser scanning confocal microscopy to study development in whole shoot apices. It was tested on angiosperm and fern apices using three fluorescent dyes; acriflavine, safranin O, and acid fuchsin, and compared with epi-illumination light microscopy and scanning electron microscopy. In all cases, acid fuchsin proved to be the best fluorochrome for examining shoot apices; having a high affinity for cell walls and nuclear material. The images produced with laser scanning confocal microscopy were sharper and clearer than images generated with epi-illumination light microscopy and scanning electron microscopy. Laser scanning confocal microscopy allows one to map patterns of cell division on the surface of an apical meristem, which is extremely difficult using other techniques such as scanning electron microscopy or epi-illumination light microscopy. Since the laser scanning light microscope records images digitally a method for digital plate production is described. Our methods can easily be applied to study the development of other plant structures on a cellular level such as root apical meristems, floral meristems, stomata, or trichomes, and reproductive organs in lower plants.Key words: confocal microscopy, apical meristem, development, fluorochrome, cytokinesis.
42
Khalil, M. M. A., M. M. Samy, A. M. H. Abd El Aal e A. H. Hamed. "The Effect of Light Quality and Intensity on <em>in vitro</em> Potato Cultures". Journal of Agricultural Sciences – Sri Lanka 18, n. 3 (5 settembre 2023): 364–74. http://dx.doi.org/10.4038/jas.v18i3.9930.
Testo completoAbstract (sommario):
Purpose: The study investigates the effect of light quality and intensity factors on in vitro potato meristem cultures and multiplication for optimization of pre-basic seed potato productions of some potato varieties.Research Method: In vitro experiments were conducted to study the response of meristems and nodal cuttings of five potato varieties, i.e., Cara, Hermes, Lady Rosetta, Santana, and Spunta, to four LED light qualities (blue, red, red+blue, or white) for five potato varities. Also, the response of nodal cuttings was examined under three light intensities (50, 75 and 100 μmol m-2 s-1).Findings: Significant differences were obtained between the four tested light qualities. Red LED gave the best meristem survival rates of the Cara, Hermes, Lady Rosetta, and Spunta potato varieties. In the multiplication phase, a significantly (p ≤ 0.05) higher plantlet length was obtained from nodal cuttings under red light quality. Also, white and red light produced vigorous plantlets, expressed as higher significant dry weight (82.2 and 80.4 mg/plantlet, respectively). Increasing light intensity from 50 to 75 and 100 μmol m-2 s-1 resulted in increases in leaf number, stem diameter, root length, leaf area, chlorophyll content, fresh weight, and dry weight.Originality/value: White LED light quality enhanced in vitro initiation of potato meristems. Furthermore, Light intensity of 75 μmol m-2 s-1 gave better performance of potato plantlets in vitro.
43
Crawford, Brian C. W., Jared Sewell, Greg Golembeski, Carmel Roshan, Jeff A. Long e Martin F. Yanofsky. "Genetic control of distal stem cell fate within root and embryonic meristems". Science 347, n. 6222 (22 gennaio 2015): 655–59. http://dx.doi.org/10.1126/science.aaa0196.
Testo completoAbstract (sommario):
The root meristem consists of populations of distal and proximal stem cells and an organizing center known as the quiescent center. During embryogenesis, initiation of the root meristem occurs when an asymmetric cell division of the hypophysis forms the distal stem cells and quiescent center. We have identified NO TRANSMITTING TRACT (NTT) and two closely related paralogs as being required for the initiation of the root meristem. All three genes are expressed in the hypophysis, and their expression is dependent on the auxin-signaling pathway. Expression of these genes is necessary for distal stem cell fate within the root meristem, whereas misexpression is sufficient to transform other stem cell populations to a distal stem cell fate in both the embryo and mature roots.
44
Muccee, Fatima. "In-silico characterization of meristem defective (MDF) protein associated with regulation of root meristems in Arabidopsis thaliana". Pakistan Journal of Science 76, n. 01 (28 marzo 2024): 76–83. http://dx.doi.org/10.57041/pjs.v76i01.1092.
Testo completoAbstract (sommario):
Meristem defective protein (MDF) plays its role in proper development of meristem patterns in Arabidopsis through regulation of auxins homeostasis. It also enables plants to survive in stress. Present study was designed to characterize MDF protein in A. thaliana to get an insight into its molecular aspects. Sequence of protein was retrieved from uniprot database and subjected to CELLO, SOPMA, SWISSMODEL, MEME server and SRING tools. The protein was also docked with four proteins i. e. SR4, RSZ33, PLT1, 2 and 3. The protein was found to localize in nucleus with secondary structure comprising of alpha helix (47.20%), extended strand (6.34%), beta turn (5.37%) and random coil (41.10%). MDF was analyzed as a conserved protein with monomeric structure. Proteins observed as interacting partners of MDF included STA1, T13D8.9, LSM5, LSM2, LSM4 and LSM8. Docking analysis revealed highest and lowest affinities of MDF binding with RS4, RZS33, PLT1, PLT2 and PLT3 in case of FGRTLTPKEAFRLLSHKFHG and IQGQTTHTFEDLNSSAKVSSDYFSQ conserved motifs, respectively. Features of MDF protein explored in this investigation can be exploited for engineering and production of plants with efficient root meristems development.
45
Limbana, Therese Anne, Louis Concepcion, Azel Baron, Blessy Gascon, Giselle Godin, Mary e Margaret Amistoso. "The Anti-Mitotic Effects of Annona Muricata Extracts to Allium Cepa Root Meristems". Journal of Knowledge Learning and Science Technology ISSN: 2959-6386 (online) 2, n. 1 (16 marzo 2023): 163–79. http://dx.doi.org/10.60087/jklst.vol2.n1.p294.
Testo completoAbstract (sommario):
Guyabano (Annona muricata) harbors a wide array of bioactive compounds that confer significant therapeutic properties. In an attempt to uncover its anti-cancer properties, we investigated the antimitotic effects of guyabano seed extracts on onion (Allium cepa) root meristems.
Methods
The present study utilized the Posttest Only Control Group Design. Onion root meristems were exposed to four distinct concentrations of aqueous and ethanolic extracts of guyabano seeds for 48 hours. For baseline conditions, the negative control group was treated with water whereas the positive control group received methotrexate.
Results
Among the various concentrations of guyabano seed extract treatments, the 800mg/100mL concentration exhibited the lowest mean mitotic index (MMI) in both aqueous and ethanolic solutions (40.33±24.50 and 32.00±9.85, respectively). However, statistical analysis revealed no significant differences between the aqueous and ethanolic treatment concentrations when compared to the negative and positive controls (P=0.40).
Conclusion
The antimitotic effects of aqueous and ethanolic seed extracts of guyabano on onion root meristems were found to be insignificant. However, the lower MMI of both aqueous and ethanolic concentrations of 800mg/100 mL guyabano compared to positive control (methotrexate) warrants further research to assess the antimitotic effects of guyabano.
46
Wang, Dandan, Xiaoxiao Ma, Zhaodong Hao, Xiaofei Long, Jisen Shi e Jinhui Chen. "Overexpression of Liriodenron WOX5 in Arabidopsis Leads to Ectopic Flower Formation and Altered Root Morphology". International Journal of Molecular Sciences 24, n. 2 (4 gennaio 2023): 906. http://dx.doi.org/10.3390/ijms24020906.
Testo completoAbstract (sommario):
Roots are essential for plant growth, and studies on root-related genes, exemplified by WUSCHEL-RELATED HOMEOBOX5 (WOX5), have mainly concentrated on model organisms with less emphasis on the function of these genes in woody plants. Here, we report that overexpression of the WOX5 gene from Liriodendron hybrid (LhWOX5) in Arabidopsis leads to significant morphological changes in both the aerial and subterranean organs. In the Arabidopsis aerial parts, overexpression of LhWOX5 results in the production of ectopic floral meristems and leaves, possibly via the ectopic activation of CLV3 and LFY. In addition, in the Arabidopsis root, overexpression of LhWOX5 alters root apical meristem morphology, leading to a curled and shortened primary root. Importantly, these abnormal phenotypes in the aerial and subterranean organs caused by constitutive ectopic expression of LhWOX5 mimic the observed phenotypes when overexpressing AtWUS and AtWOX5 in Arabidopsis, respectively. Taken together, we propose that the LhWOX5 gene, originating from the Magnoliaceae plant Liriodendron, is a functional homolog of the AtWUS gene from Arabidopsis, while showing the highest degree of sequence similarity with its ortholog, AtWOX5. Our study provides insight into the potential role of LhWOX5 in the development of both the shoot and root.
47
HIDALGO, A., J. A. GONZALEZ-REYES e P. NAVAS. "Ascorbate free radical enhances vacuolization in onion root meristems". Plant, Cell and Environment 12, n. 4 (giugno 1989): 455–60. http://dx.doi.org/10.1111/j.1365-3040.1989.tb01962.x.
Testo completo
48
GIMENEZABIAN, M., J. RUFAS e C. DELATORRE. "Response of interphasic nucleoli to hypoxia in root meristems". Cell Biology International Reports 9, n. 8 (agosto 1985): 699–708. http://dx.doi.org/10.1016/0309-1651(85)90077-3.
Testo completo
49
Peterson, R. L. "Adaptations of root structure in relation to biotic and abiotic factors". Canadian Journal of Botany 70, n. 4 (1 aprile 1992): 661–75. http://dx.doi.org/10.1139/b92-087.
Testo completoAbstract (sommario):
Roots are discussed less frequently than other plant organs in terms of their phylogenetic origin and evolutionary specialization because of limited paleobotanical information and few broad comparative studies of root structure and development. There is considerable diversity, however, in root structure among the major groups of vascular plants. Roots of many extinct and extant seedless vascular plants have a simple apical meristem (i.e., an apical cell), limited secondary growth, and in some genera, branching is accomplished by a true dichotomy of the apical meristem. Roots of seed plants evolved more complex apical meristems, branching from subterminal tissues, and in some groups extensive vascular cambium activity. Evolutionary developments related to nutrient availability include symbiotic interactions with soil fungi to form mycorrhizae, soil bacteria and cyanobacteria to form nitrogen-fixing nodules, and the modification of branching to form cluster roots. Concomitant with these specializations, root hair frequency and structure are often modified. All roots possess a suberized layer, the endodermis, and in many species, particularly among the angiosperms, a specialized suberized exodermis is present. Roots of aquatic species have evolved mechanisms either to tolerate or to avoid anaerobiosis. Roots growing in continuously wet environments possess constitutive aerenchyma whereas roots of periodically flooded plants are able to respond by forming lysigenous or schizogenous aerenchyma. Key words: roots, evolution, adaptations, structure, symbioses.
50
Thies, Karen L., e Clinton H. Graves. "Meristem Micropropagation Protocols for Vitis rotundifolia Michx." HortScience 27, n. 5 (maggio 1992): 447–49. http://dx.doi.org/10.21273/hortsci.27.5.447.
Testo completoAbstract (sommario):
A meristem micropropagation system was developed to produce Agrobacterium -free muscadine grape. Meristems were cultured on a modified Woody Plant Medium (mWPM) supplemented with 0.45 μm BAP. After 2 weeks, cultures were transferred to mWPM containing 8.92 μm BAP to enhance shoot proliferation. Propagules were subsequently subdivided and transferred to fresh medium at 2- to 4-week intervals. New shoots were excised and inserted in mWPM supplemented with 0.57 μm IAA to promote root formation. This method has been successfully used to produce Agrobacterium -free plants of muscadine cultivars Carlos, Doreen, Jumbo, Magnolia, and Sterling for research purposes and for a foundation planting in Mississippi. Chemical names used: benzylaminopurine (BAP); indole3-acetic acid (IAA).