Nonpolar movement of N6-benzyladenine-14C in coleoptile, stem, petiole, and floral organ sections

1973 ◽  
Vol 51 (11) ◽  
pp. 2079-2083 ◽  
Author(s):  
James L. Koevenig
Keyword(s):  
Avena Sativa ◽  
Time Course ◽  
Floral Organ ◽  
Scintillation Counting ◽  
Passive Diffusion ◽  
Plant Organs ◽  
Polar Movement ◽  
Metabolic Difference

Movement of N6-benzyladenine-methylene-14C in Avena sativa coleoptiles, Colens blumei stems and petioles, and Cleome hassleriana stamen filaments, gynophores, and pedicels was studied by suspending sections horizontally between donor and receiver agar cylinders and determining radioactivity in receivers by scintillation counting. No polar movement was found in any of the plant organs. In time-course experiments using oat coleoptiles, the amount of radioactivity in receivers continued to increase for 24 h and the velocity was 1.5-2 mm/h, suggesting movement by passive diffusion. More radioactivity moved through stamen filaments and gynophore sections from mature expanded flowers than through those from young buds, apparently as a result of larger uptake and exit areas in expanded flowers. A significantly greater acropetal and basipetal movement through young pedicels is not due to area differences and probably results from a metabolic difference.

scholarly journals Comparative Time-Course Physiological Responses and Proteomic Analysis of Melatonin Priming on Promoting Germination in Aged Oat (Avena sativa L.) Seeds

2021 ◽  
Vol 22 (2) ◽  
pp. 811
Author(s):  
Huifang Yan ◽  
Peisheng Mao
Keyword(s):  
Antioxidant Capacity ◽  
Avena Sativa ◽  
Proteomic Analysis ◽  
Time Course ◽  
Intact Cell ◽  
Membrane Integrity ◽  
Acid Synthesis ◽  
Ultrastructural Changes ◽  
Oat Seeds ◽  
Aged Seeds

Melatonin priming is an effective strategy to improve the germination of aged oat (Avena sativa L.) seeds, but the mechanism involved in its time-course responses has remained largely unknown. In the present study, the phenotypic differences, ultrastructural changes, physiological characteristics, and proteomic profiles were examined in aged and melatonin-primed seed (with 10 μM melatonin treatment for 12, 24, and 36 h). Thus, 36 h priming (T36) had a better remediation effect on aged seeds, reflecting in the improved germinability and seedlings, relatively intact cell ultrastructures, and enhanced antioxidant capacity. Proteomic analysis revealed 201 differentially abundant proteins between aged and T36 seeds, of which 96 were up-accumulated. In melatonin-primed seeds, the restoration of membrane integrity by improved antioxidant capacity, which was affected by the stimulation of jasmonic acid synthesis via up-accumulation of 12-oxo-phytodienoic acid reductase, might be a candidate mechanism. Moreover, the relatively intact ultrastructures enabled amino acid metabolism and phenylpropanoid biosynthesis, which were closely associated with energy generation through intermediates of pyruvate, phosphoenolpyruvate, fumarate, and α-ketoglutarate, thus providing energy, active amino acids, and secondary metabolites necessary for germination improvement of aged seeds. These findings clarify the time-course related pathways associated with melatonin priming on promoting the germination of aged oat seeds.

scholarly journals Acetylcholine Receptors

1972 ◽  
Vol 60 (3) ◽  
pp. 248-262 ◽  
Author(s):  
H. Criss Hartzell ◽  
Douglas M. Fambrough
Keyword(s):  
Acetylcholine Receptors ◽  
Time Course ◽  
Plasma Membranes ◽  
Scintillation Counting ◽  
Receptor Density ◽  
Rat Diaphragm ◽  
Leg Muscles ◽  
And Function ◽  
Quantitative Radioautography ◽  
Ach Receptors

Using 125iodine-labeled α-bungarotoxin (α-BGT-125I) and quantitative radioautography, we have studied the time-course of the change in acetylcholine (ACh) receptor distribution and density occurring in rat diaphragm after denervation. In innervated fibers, ACh receptors are localized at the neuromuscular junction and the extrajunctional receptor density is less than five receptors per square micrometer. The extrajunctional receptor density begins to increase between 2 and 3 days after denervation and increases approximately linearly to 1695 receptors/µm2 at 14 days, subsequently decreasing to 529 receptors/µm2 at 45 days. We have isolated plasma membranes from rat leg muscles at various times after denervation and find that the change in concentration of ACh receptors in the membranes measured by α-BGT-125I binding and scintillation counting follows a time-course similar to the change in ACh receptor density measured radioautographically. Furthermore, we have correlated extrajunctional ACh receptor density measured by radioautography with extrajunctional ACh sensitivity measured by iontophoretic application of ACh and intracellular recording and find that the log of ACh receptor density is related to 0.53 times the log of ACh sensitivity. These results are discussed in terms of the electrophysiological experiments on the ACh receptor and the recent, more biochemical approaches to the study of ACh receptor control and function.

THE TIME-COURSE OF POLAR MOVEMENT OF GIBBERELLIN THROUGH ZEA ROOTS

1973 ◽  
Vol 60 (9) ◽  
pp. 896-900 ◽  
Author(s):  
W. P. Jacobs ◽  
Paula E. Pruett
Keyword(s):  
Time Course ◽  
Polar Movement

scholarly journals The integration of plant behaviour. III.- The effect of gravity on the growth of roots

1931 ◽  
Vol 108 (758) ◽  
pp. 360-365 ◽  
Keyword(s):  
Avena Sativa ◽  
Growth Substance ◽  
Horizontal Axis ◽  
Horizontal Position ◽  
Growth Substances ◽  
Plant Organs ◽  
Rate Of Growth ◽  
Interesting Discussion ◽  
Plant Behaviour

The question whether the transverse stimulus of gravity affects the rate of growth of various parts of plants has been often investigated, but with results that are in part very contradictory. For a convenient discussion of the results obtained up to 1925, reference may be made to a paper by Gradmann (1925, p. 237). More recently Dolk (1929) has obtained automatic records of the growth of Avena coleeptiles when rotated on the horizontal axis of the clinostat and when placed vertical. His records, which seem quite free from objection, show so uniform a rate of growth that it must be concluded that in these plant organs in these conditions the change from the vertical to the horizontal position, or vice versa , makes no difference to the rate of growth. Cholodny also has obtained evidence that in hypocotyls of Lupinus and Helianthus (1929) and in coleoptiles of Avena sativa (1930), the rate of growth id not affected by their position in relation to gravity. Dolk and Cholodny interpret these results in favour of the Cholodny-Went theory of geotropism, according to which the geotropic curvatures of roots and coleoptiles are brought about by growth-substances continually secreted by the tips, which become re-distributed between the upper and lower sides under the stimulus of gravity, though their total quantity is supposed not to be changed. Now the writers regard this theory favourably, but none the less it appears to them that even if this re-distribution does takes place, and even if it suffices to account for the geotropic curvatures, it remains possible that in some that organs at least the transverse stimulus of gravity may also alter the total quantity of growth-substance. This point has been emphasised by Gradmann in an interesting discussion (1930, p. 596). Actually it is well known that in the nodes of grasses the transverse stimulus of gravity does alter the rate of growth. For nodes that have completed their growth may start growing again if placed horizontal.

SEM Cold Stage Techniques for the Observation of Vegetative and Floral Apices of Oat (Avena sativa L.) Plants

1977 ◽  
Vol 35 ◽  
pp. 590-591
Author(s):  
B. K. Kirchoff ◽  
L.F. Allard ◽  
W.C. Bigelow
Keyword(s):  
Critical Point ◽  
Avena Sativa ◽  
Substantial Improvement ◽  
Fresh Tissue ◽  
Cold Stage ◽  
Critical Point Drying ◽  
Almost All ◽  
Cell Collapse ◽  
Conductive Paint ◽  
Carbon Based

In attempting to use the SEM to investigate the transition from the vegetative to the floral state in oat (Avena sativa L.) it was discovered that the procedures of fixation and critical point drying (CPD), and fresh tissue examination of the specimens gave unsatisfactory results. In most cases, by using these techniques, cells of the tissue were collapsed or otherwise visibly distorted. Figure 1 shows the results of fixation with 4.5% formaldehyde-gluteraldehyde followed by CPD. Almost all cellular detail has been obscured by the resulting shrinkage distortions. The larger cracks seen on the left of the picture may be due to dissection damage, rather than CPD. The results of observation of fresh tissue are seen in Fig. 2. Although there is a substantial improvement over CPD, some cell collapse still occurs.Due to these difficulties, it was decided to experiment with cold stage techniques. The specimens to be observed were dissected out and attached to the sample stub using a carbon based conductive paint in acetone.

Ultrastructural Changes of the Symbiotic Chlorella-Like Alga Isolated from Hydra Viridis

1982 ◽  
Vol 40 ◽  
pp. 320-321
Author(s):  
K.W. Lee ◽  
R.H. Meints ◽  
D. Kuczmarski ◽  
J.L. Van Etten
Keyword(s):  
Time Course ◽  
Reciprocal Cross ◽  
Ultrastructural Level ◽  
Ultrastructural Changes ◽  
Symbiotic Relationship ◽  
Cell Recognition ◽  
Green Hydra ◽  
Different Strains ◽  
Hydra Viridis

The physiological, biochemical, and ultrastructural aspects of the symbiotic relationship between the Chlorella-like algae and the hydra have been intensively investigated. Reciprocal cross-transfer of the Chlorellalike algae between different strains of green hydra provide a system for the study of cell recognition. However, our attempts to culture the algae free of the host hydra of the Florida strain, Hydra viridis, have been consistently unsuccessful. We were, therefore, prompted to examine the isolated algae at the ultrastructural level on a time course.

Destruction of Actin Filaments by Osmium Tetroxide

1977 ◽  
Vol 35 ◽  
pp. 466-467
Author(s):  
P. Maupin-Szamier ◽  
T. D. Pollard
Keyword(s):  
Actin Filaments ◽  
Time Course ◽  
Osmium Tetroxide ◽  
Rabbit Muscle ◽  
Muscle Actin ◽  
Sodium Phosphate Buffer ◽  
Transmission Electron ◽  
The Difference ◽  
Rates Of Decay ◽  
Short Time

We have studied the destruction of rabbit muscle actin filaments by osmium tetroxide (OSO4) to develop methods which will preserve the structure of actin filaments during preparation for transmission electron microscopy.Negatively stained F-actin, which appears as smooth, gently curved filaments in control samples (Fig. 1a), acquire an angular, distorted profile and break into progressively shorter pieces after exposure to OSO4 (Fig. 1b,c). We followed the time course of the reaction with viscometry since it is a simple, quantitative method to assess filament integrity. The difference in rates of decay in viscosity of polymerized actin solutions after the addition of four concentrations of OSO4 is illustrated in Fig. 2. Viscometry indicated that the rate of actin filament destruction is also dependent upon temperature, buffer type, buffer concentration, and pH, and requires the continued presence of OSO4. The conditions most favorable to filament preservation are fixation in a low concentration of OSO4 for a short time at 0°C in 100mM sodium phosphate buffer, pH 6.0.

The time course of calcium deposition in shells of the barnacle (Balanus amphititre amphititre) during cyprid-juvenile metamorphosis

1994 ◽  
Vol 52 ◽  
pp. 178-179
Author(s):  
Nancy R. Wallace ◽  
Craig C. Freudenrich ◽  
Karl Wilbur ◽  
Peter Ingram ◽  
Ann LeFurgey
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Time Course ◽  
Vertical Plane ◽  
Mantle Cavity ◽  
Qualitative Assessment ◽  
Calcium Deposition ◽  
Free Swimming ◽  
Freeze Dried ◽  
Scanning Electron

The morphology of balanomorph barnacles during metamorphosis from the cyprid larval stage to the juvenile has been examined by light microscopy and scanning electron microscopy (SEM). The free-swimming cyprid attaches to a substrate, rotates 90° in the vertical plane, molts, and assumes the adult shape. The resulting metamorph is clad in soft cuticle and has an adult-like appearance with a mantle cavity, thorax with cirri, and incipient shell plates. At some time during the development from cyprid to juvenile, the barnacle begins to mineralize its shell, but it is not known whether calcification occurs before, during, or after ecdysis. To examine this issue, electron probe x-ray microanalysis (EPXMA) was used to detect calcium in cyprids and juveniles at various times during metamorphosis.Laboratory-raised, free-swimming cyprid larvae were allowed to settle on plastic coverslips in culture dishes of seawater. The cyprids were observed with a dissecting microscope, cryopreserved in liquid nitrogen-cooled liquid propane at various times (0-24 h) during metamorphosis, freeze dried, rotary carbon-coated, and examined with scanning electron microscopy (SEM). EPXMA dot maps were obtained in parallel for qualitative assessment of calcium and other elements in the carapace, wall, and opercular plates.

Arabidopsis 4-COUMAROYL-COA LIGASE 8 contributes to the biosynthesis of the benzenoid ring of coenzyme Q in peroxisomes

2019 ◽  
Vol 476 (22) ◽  
pp. 3521-3532
Author(s):  
Eric Soubeyrand ◽  
Megan Kelly ◽  
Shea A. Keene ◽  
Ann C. Bernert ◽  
Scott Latimer ◽  
...  
Keyword(s):  
Oxidative Metabolism ◽  
Time Course ◽  
Reverse Genetics ◽  
De Novo ◽  
Coenzyme Q ◽  
Control Level ◽  
Wild Type ◽  
Fluorescent Reporters ◽  
Coa Ligase ◽  
Peroxisomal Targeting

Plants have evolved the ability to derive the benzenoid moiety of the respiratory cofactor and antioxidant, ubiquinone (coenzyme Q), either from the β-oxidative metabolism of p-coumarate or from the peroxidative cleavage of kaempferol. Here, isotopic feeding assays, gene co-expression analysis and reverse genetics identified Arabidopsis 4-COUMARATE-COA LIGASE 8 (4-CL8; At5g38120) as a contributor to the β-oxidation of p-coumarate for ubiquinone biosynthesis. The enzyme is part of the same clade (V) of acyl-activating enzymes than At4g19010, a p-coumarate CoA ligase known to play a central role in the conversion of p-coumarate into 4-hydroxybenzoate. A 4-cl8 T-DNA knockout displayed a 20% decrease in ubiquinone content compared with wild-type plants, while 4-CL8 overexpression boosted ubiquinone content up to 150% of the control level. Similarly, the isotopic enrichment of ubiquinone's ring was decreased by 28% in the 4-cl8 knockout as compared with wild-type controls when Phe-[Ring-13C6] was fed to the plants. This metabolic blockage could be bypassed via the exogenous supply of 4-hydroxybenzoate, the product of p-coumarate β-oxidation. Arabidopsis 4-CL8 displays a canonical peroxisomal targeting sequence type 1, and confocal microscopy experiments using fused fluorescent reporters demonstrated that this enzyme is imported into peroxisomes. Time course feeding assays using Phe-[Ring-13C6] in a series of Arabidopsis single and double knockouts blocked in the β-oxidative metabolism of p-coumarate (4-cl8; at4g19010; at4g19010 × 4-cl8), flavonol biosynthesis (flavanone-3-hydroxylase), or both (at4g19010 × flavanone-3-hydroxylase) indicated that continuous high light treatments (500 µE m−2 s−1; 24 h) markedly stimulated the de novo biosynthesis of ubiquinone independently of kaempferol catabolism.

Sign in / Sign up

Export Citation Format

Share Document