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Cellular specificity of the gravitropic motor response in roots (1997)

Evans, Michael L. ; Ishikawa, Hideo

Springer

Planta 203 (1997), S. S115

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ISSN: 1432-2048

Keywords: Key words:Arabidopsis ; Auxin ; Calcium ; Distal elongation zone ; Gravitropism (root) ; Zea

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract. A number of features of the gravitropic response of roots are not readily accounted for by the classical Cholodny-Went theory. These include the observations that (i) in the later stages of the response the growth gradient is reversed with no evident reversal of the auxin gradient; (ii) a major component of the acceleration of growth along the upper side occurs in the distal elongation zone (DEZ), a group of cells located between the meristem and the main elongation, not within the central elongation zone; and (iii) the initiation of differential growth in the DEZ appears to be independent of the establishment of auxin asymmetry. Alternative candidates for mediation of differential growth in the DEZ include calcium ions and protons. Gravi-induced curvature is accompanied by polar movement of calcium toward the lower side of the maize root tip and the DEZ is shown to be particularly sensitive to growth inhibition by calcium. Also, gravistimulation of maize roots causes enhanced acid efflux from the upper side of the DEZ. Evidence for gravi-induced modification of ion movements in the root tip includes changes in intracellular potentials and current flow. It is clear that there is more than one motor region in the root with regard to gravitropic responses and there is evidence that the DEZ itself consists of more than one class of responding cells. In order to gain a more complete understanding of the mechanism of gravitropic curvature, the physiological properties of the sub-zones of the root apex need to be thoroughly characterized with regard to their sensitivity to hormones, calcium, acid pH and electrical perturbations.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/PL00008099

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Syndiotactic 1,2-polybutadiene with Co-CS2 catalyst system. I. Preparation, properties, and application of highly crystalline syndiotactic 1,2-polybutadiene (1983)

Ashitaka, Hidetomo ; Ishikawa, Hideo ; Ueno, Haruo ; [et al.]

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 1853-1860

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ISSN: 0360-6376

Keywords: Physics ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: Highly crystalline syndiotactic 1,2-polybutadiene (s-PB) having melting point (mp) up to 216°C was obtained by using a Co(acac)3-AIEt3-CS2 catalyst. The polymer with mp 208°C was found to have 99.7% 1,2 content and 99.6% syndiotacticity by 1H and 13C-NMR measurements. The s-PB can be molded by addition of a stabilizer such as 2,6-di-t-butyl-4-hydroxymethylphenol into fiber, film, and various shaped articles. The physical properties presented in the present article include stress-strain and dynamic mechanical behavior. The highly crystalline syndiotactic 1,2-polybutadiene was applied to a carbon fiber and UBEPOL VCR (cis-1,4-polybutadiene reinforced by fibrous syndiotactic 1,2-polybutadiene).

Additional Material: 2 Ill.