197 research outputs found
Electron spin resonance shifts in S=1 antiferromagnetic chains
We discuss electron spin resonance (ESR) shifts in spin-1 Heisenberg
antiferromagnetic chains with a weak single-ion anisotropy based on several
effective field theories, the O(3) nonlinear sigma model (NLSM) in the Haldane
phase, free fermion theories around the lower and the upper critical fields. In
the O(3) NLSM, the single-ion anisotropy corresponds to a composite operator
which creates two magnons at the same time and position. Therefore, even inside
a parameter range where free magnon approximation is valid, we have to take
interactions among magnons into account. Though the O(3) NLSM is only valid in
the Haldane phase, an appropriate translation of Faddeev-Zamolodchikov
operators of the O(3) NLSM to fermion operators enables one to treat ESR shifts
near the lower critical field in a similar manner to discussions in Haldane
phase. We present that our theory gives quantitative agreements with recent ESR
experimental results on an spin-1 chain compounds NDMAP
Phototactic Responses of Cell Population to Repeated Pulses of Yellow Light in a Phytoflagellate Cryptomonas
Phototactic responses of cell population to repeated pulses of yellow light in a phytoflagellate Cryptomonas sp.
Positive phototaxis in cell populations of a phytoflagellate Cryptomonas sp. was recorded photoelectrically when the duration and intensity of repeated pulses of monochromatic yellow light (570 nm) interspersed with darkness were varied. Irrespective of the duration of the light pulses, phototactic responses to repeated pulses were as great as those to continuous irradiation and were linearly dependent on the logarithm of total incident light energy when the dark interval was shorter than 60 milliseconds. Under these conditions, reciprocity between duration and intensity held well. In contrast, when the dark interval exceeded 250 milliseconds, the responses were remarkably reduced regardless of light duration and were not affected by increasing the intensity of actinic light pulses. The present results clearly indicate that continuous stimulation with actinic light is not essential for the maximum effect, but that the length of dark interval is crucial in phototactic response
Auxin responsiveness of a novel cytochrome P450 in rice coleoptiles
An early auxin-induced gene was isolated from rice (Oryza sativa
L. subsp. japonica cv Nihonmasari) coleoptiles by a
fluorescent-labeled differential display screen. The full-length
gene contains conserved domains characteristic for the
cytochrome P450 superfamily. This gene, designated as CYP87A3,
was weakly expressed in dark-grown coleoptiles but was
up-regulated rapidly and transiently when coleoptile segments
were incubated in 5 m indole-3-acetic acid. This induction
by auxin could not be suppressed by cycloheximide. Depletion of
segments from endogenous auxin reduced the amount of CYP87A3
transcripts. The CYP87A3 transcript level was rapidly, although
transiently, up-regulated in response to light as well. The
observed pattern of gene regulation might indicate a role in the
suppression of auxin-induced coleoptile growth.
The role of CYP87A3 is discussed with respect to auxin signaling
in the regulation of coleoptile growth
Phytochrome-dependent Reduction of Nicotinamide Nucleotides in the Mitochondrial Fraction Isolated from Etiolated Pea Epicotyls
A Rapid Phytochrome-dependent Reduction of Nicotinamide Adenine Dinucleotide Phosphate in Particle Fraction from Etiolated Bean Hypocotyl
Single-ion anisotropy in Haldane chains and form factor of the O(3) nonlinear sigma model
We consider spin-1 Haldane chains with single-ion anisotropy, which exists in
known Haldane chain materials. We develop a perturbation theory in terms of
anisotropy, where magnon-magnon interaction is important even in the low
temperature limit. The exact two-particle form factor in the O(3) nonlinear
sigma model leads to quantitative predictions on several dynamical properties
including dynamical structure factor and electron spin resonance frequency
shift. These agree very well with numerical results, and with experimental data
on the Haldane chain material Ni(CHN)N(PF)
Impaired induction of the Jasmonate Pathway in the rice mutant hebiba
The elongation of rice (Oryza sativa) coleoptiles is inhibited
by light, and this photoinhibition was used to screen for
mutants with impaired light response. In one of the isolated
mutants, hebiba, coleoptile elongation was stimulated in the
presence of red light, but inhibited in the dark. Light
responses of endogenous indolyl-3-acetic acid and abscisic acid
were identical between the wild type and the mutant. In
contrast, the wild type showed a dramatic increase of jasmonate
heralded by corresponding increases in the content of its
precursor o-phytodienoic acid, whereas both compounds were not
detectable in the mutant. The jasmonate response to wounding was
also blocked in the mutant. The mutant phenotype was rescued by
addition of exogenous methyl jasmonate and o-phytodienoic acid.
Moreover, the expression of O. sativa 12-oxophytodienoic acid
reductase, an early gene of jasmonic acid-synthesis, is induced
by red light in the wild type, but not in the mutant. This
evidence suggests a novel role for jasmonates in the light
response of growth, and we discuss a cross-talk between
jasmonate and auxin signaling. In addition, hebiba represents
the first rice mutant in which the induction of the jasmonate
pathway is impaired providing a valuable tool to study the role
of jasmonates in Graminean development
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