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1.
Cotyledon explants of ginseng (Panax ginseng C. A. Meyer) produced somatic embryos directly on medium without growth regulators, with 89% of the explants forming somatic
embryos. Cytokinin treatment greatly suppressed somatic embryo formation but stimulated the direct formation of adventitious
buds. BAP treatment was more effective than the kinetin treatment for adventitious bud formation. Auxin (0.05 mg/l IBA) in
combination with cytokinin enhanced adventitious bud formation, with the highest frequency, 40%, at 0.05 mg/l IBA and 5 mg/l
BAP. Adventitious buds were mainly formed near the distal portion of the cotyledons, while somatic embryos were formed near
the proximal excised margins. Shoots were developed from adventitious buds after transfer to MS medium with 10 mg/l GA3. Root formation from the shoots was obtained after the shoots were transferred to half-strength MS medium with auxin (IAA).
When the plants derived from adventitious buds were transferred to greenhouse soil, 36% were successfully acclimatized.
Received: 7 November 1997 / Revision received: 12 January 1998 / Accepted: 7 February 1998 相似文献
2.
Summary Rapid formation of adventitious roots by walnut cotyledon fragments in vitro was traced by light microscopy. It was shown that this plant model is characterized by two major developmental processes: a) confined elongation of the cotyledon petiole caused by a limited number of cell divisions and b) formation of a morphogenetic zone around each initially wounded vascular bundle within 36 h after detachment of the embryonic axis. During the first phase of development, granular storage protein bodies dissolved, and starch grains were deposited mainly in the distal portion of the cotyledon fragments. Rapidly, new globular protein bodies were formed, and phenolic inclusions accumulated in the vacuoles of epidermal and subepidermal cells and of individual cells close to the vascular bundles. Each adventitious root was found to be in continuity with a single vascular bundle of the cotyledon petiole. A short auxin treatment suppressed the formation of large roots and induced numerous tiny rootlets dispersed all over the surface of the cotyledons.Abbreviations IBA
indole-3-butyric acid 相似文献
3.
4.
H. Y. Seo Y. J. Kim T. I. Park H. S. Kim S. J. Yun K. H. Park M. K. Oh M. Y. Choi C. H. Paik Y. S. Lee Y. E. Choi 《In vitro cellular & developmental biology. Plant》2007,43(3):209-214
Sesamum indicum L. was used as an important oil crop in the world. An efficient protocol for in vitro plant regeneration via adventitious shoot formation from deembryonated cotyledon explants isolated from mature seeds of sesame
is developed. Optimal medium for direct adventitious shoot formation was Murashige and Skoog (MS) medium with 22.2 μM 6-benzylaminopurin
(BA) and 5.7 μM indole-3-acetic acid (IAA). Abscisic acid (3.8 μM ABA) and AgNO3 (29.4 μM) were effective in enhancing the frequency of adventitious shoot formation. Preculture of cotyledon explants on
high sucrose concentration (6–9%) for 2 wk and subsequent transfer to 3% sucrose enhanced the frequency of adventitious shoot
induction. Root formation from the adventitious shoots was easily achieved on MS medium containing 2.7 μM of α-naphthalene
acetic acid (NAA). Regenerated plantlets were acclimatized on sand and peat moss (1:1), showing 95% survival with subsequent
flowering and seed set. We established the high-frequency plant regeneration via adventitious shoot formation in S. indicum L. 相似文献
5.
Two isoforms of chalcone synthase (CHS) were isolated from cDNA libraries derived from UV-A-irradiated anthocyanin-accumulating
(DCb) and non-accumulating (DCs) cell cultures of carrot (Daucus carota L.). The clones designated as DcCHS1, which were present only in the DCb library, had a deduced primary sequence of 389 amino
acids and an expected molecular mass of 42.7 kDa, and seem to be alleles of those cloned by Ozeki et al. (1993). The second
isoform (DcCHS2) was present in both libraries. It had the highest degree of similarity (97.7%) to parsley CHS over all 397
amino acids. The expected molecular mass of the corresponding protein was 43.6 kDa. Results obtained from Southern blot analysis
indicated the existence of at least two CHS genes in carrot. A transient enhancement of the DcCHS1 mRNA level after continuous
irradiation with UV-A light could only be observed in anthocyanin-accumulating cultures, whereas an increase in DcCHS2 mRNA
was seen in both cell lines. The maximum accumulation of CHS mRNA occurred 48 h after the onset of UV-A irradiation. In the
European wild carrot the accumulation of DcCHS1 mRNA was restricted to the red central flowers, whereas the DcCHS2 mRNA was
detectable in all red and white petals, as well as leaves, but was absent in stems and roots. The expression of DcCHS1 was
restricted to anthocyanin-accumulating cells or organs. The heterologous expression of both cDNAs in Escherichia coli resulted in immunostainable bands of different sizes on the Western blot and high levels of catalytic CHS activity.
Received: 2 September 1999 / Accepted: 30 November 1999 相似文献
6.
Chalcone synthase activity and polyphenolic compounds of shoot tissues from adult and rejuvenated walnut trees 总被引:3,自引:0,他引:3
Changes in the metabolism of naphthoquinone and flavonoids during the growth of half-sib adult and rejuvenated walnut shoots
(Juglans nigra × Juglans regia L.) were studied at the tissue level for two years after pruning. Moreover, the role of chalcone synthase (CHS; EC 2.3.1.74)
in the regulation of flavonoid biosynthesis was investigated at the level of enzyme activity. The end products of walnut flavonoid
biosynthesis, myricitrin and quercitrin, which accumulated in the bark and phloem at the end of growth, did not inhibit the
biosynthetic process at concentrations of up to 100 μM each. There was no evidence of CHS regulation by feedback or similar
mechanisms which might modulate enzyme activity. Mathematical correlation of CHS activity and flavonoid accumulation during
shoot growth, however, indicated that CHS is the rate-limiting enzyme of the pathway in bark and phloem and that flavonoids
seem to be transported from phloem to bark where they accumulated mainly during growth. In defoliated shoots, naphthoquinone
metabolism appeared to be a marker of the walnut rejuvenation stage in the medulla, phloem and buds immediately after cutting
and thereafter mainly in buds one year after cutting. Chalcone synthase and flavonoid contents appeared to be markers of the
adult stage in the phloem.
Received: 30 September 1996 / Accepted: 17 March 1997 相似文献
7.
Regulation and activation of phytoene synthase, a key enzyme in carotenoid biosynthesis, during photomorphogenesis 总被引:12,自引:0,他引:12
During photomorphogenesis in higher plants, a coordinated increase occurs in the chlorophyll and carotenoid contents. The
carotenoid level is under phytochrome control, as reflected by the light regulation of the mRNA level of phytoene synthase
(PSY), the first enzyme in the carotenoid biosynthetic pathway. We investigated PSY protein levels, enzymatic activity and
topological localization during photomorphogenesis. The results revealed that PSY protein levels and enzymatic activity increase
during de-etiolation and that the enzyme is localized at thylakoid membranes in mature chloroplasts. However, under certain
light conditions (e.g., far-red light) the increases in PSY mRNA and protein levels are not accompanied by an increase in
enzymatic activity. Under those conditions, PSY is localized in the prolamellar body fraction in a mostly enzymatically inactive
form. Subsequent illumination of dark-grown and/or in far-red light grown seedlings with white light causes the decay of these
structures and a topological relocalization of PSY to developing thylakoids which results in its enzymatic activation. This
light-dependent mechanism of enzymatic activation of PSY in carotenoid biosynthesis shares common features with the regulation
of the NADPH:protochlorophyllide oxidoreductase, the first light-regulated enzyme in chlorophyll biosynthesis. The mechanism
of regulation described here may contribute to ensuring a spatially and temporally coordinated increase in both carotenoid
and chlorophyll contents.
Received: 14 February 2000 / Accepted: 15 March 2000 相似文献
8.
Cloning and expression of UDP-glucose: flavonoid 7-O-glucosyltransferase from hairy root cultures of Scutellaria baicalensis 总被引:1,自引:0,他引:1
A cDNA encoding UDP-glucose: baicalein 7-O-glucosyltransferase (UBGT) was isolated from a cDNA library from hairy root cultures of Scutellaria baicalensis Georgi probed with a partial-length cDNA clone of a UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT) from grape (Vitis vinifera L.). The heterologous probe contained a glucosyltransferase consensus amino acid sequence which was also present in the Scutellaria cDNA clones. The complete nucleotide sequence of the 1688-bp cDNA insert was determined and the deduced amino acid sequences
are presented. The nucleotide sequence analysis of UBGT revealed an open reading frame encoding a polypeptide of 476 amino
acids with a calculated molecular mass of 53 094 Da. The reaction product for baicalein and UDP-glucose catalyzed by recombinant
UBGT in Escherichia coli was identified as authentic baicalein 7-O-glucoside using high-performance liquid chromatography and proton nuclear magnetic resonance spectroscopy. The enzyme activities
of recombinant UBGT expressed in E. coli were also detected towards flavonoids such as baicalein, wogonin, apigenin, scutellarein, 7,4′-dihydroxyflavone and kaempferol,
and phenolic compounds. The accumulation of UBGT mRNA in hairy roots was in response to wounding or salicylic acid treatments.
Received: 8 September 1999 / Accepted: 4 October 1999 相似文献
9.
Microsporogenesis in Lilium longiflorum Thunb. is a naturally synchronous process and affords a system in which to study stage-specific events of meiosis and anther
development. Zymogram gel analyses were conducted with extracts from a variety of stages of anther development to identify
proteinases which likely play roles in anther metabolism. These experiments revealed that several proteinases are present
at different stages of anther development, and class-specific inhibitors were used to classify these enzymes. Proteolytic
activities increased as anther development proceeded and these activities were temporally correlated with the apoptotic events
which precede dehiscence, as well as with events crucial for the maturation of viable pollen.
Received: 12 October 1999 / Accepted: 13 November 1999 相似文献
10.
Levels of endogenous indole-3-acetic acid and indole-3-acetylaspartic acid during adventitious root formation in pea cuttings 总被引:6,自引:0,他引:6
Levels of endogenous indole-3-acetic acid (IAA) and indole-3-acetylaspartic acid (IAAsp) were monitored in various parts of leafy cuttings of pea ( Pisum sativum L. cv. Marma) during the course of adventitious root formation. IAA and IAAsp were identified by combined gas chromatography—mass spectrometry, and the quantitations were performed by means of high performance liquid chromatography with spectrofluorometric detection. IAA levels in the root forming tissue of the stem base, the upper part of the stem base (where no roots were formed), and the shoot apex remained constant during the period studied and were similar to levels occurring in the intact seedling. A reduction of the IAA level in the root regenerating zone, achieved by removing the shoot apex, resulted in almost complete inhibition of root formation. The IAAsp level in the shoot apex also remained constant, whereas in the stem base it increased 6-fold during the first 3 days. These results show that root initiation may occur without increased IAA levels in the root regenerating zone. It is concluded that the steady-state concentration is maintained by basipetal IAA transport from the shoot apex and by conjugation of excessive IAA with aspartic acid, thereby preventing accumulation of IAA in the tissue. 相似文献
11.
Heteroblasty in Arabidopsis thaliana was analyzed in a variety of plants with mutations in leaf morphology using a tissue-specific β-glucuronidase gene marker.
Some mutants exhibited their mutant phenotypes specifically in foliage leaves. The phenotypes associated with the foliage-leaf-specific
mutations were also found to be induced ectopically in cotyledons in the presence of the lec1 mutation. Moreover, the features of an emf1lec1 double mutant showed that cotyledons can be partially converted into carpelloids. When heteroblastic traits were examined
in foliage leaves in the presence of certain mutations or natural deviations by histochemical analysis of the expression of
the tissue-specific marker gene, it was found that ectopic expression of the developmental program for the first foliage leaves
in lec1 cotyledons seemed to affect the heteroblastic features of the first set of foliage leaves, while foliage leaves beyond the
third position appeared normal. Similarly, in wild-type plants, discrepancies in heteroblastic features, relative to standard
features, of foliage leaves at early positions seemed to be eliminated in foliage leaves at later positions. These results
suggest that heteroblasty in foliage leaves might be affected in part by the heteroblastic stage of the preceding foliage
leaves but is finally controlled autonomously at each leaf position.
Received: 9 July 1999 / Accepted: 17 August 1999 相似文献
12.
Yun-He Li Qi-Zhu Chen Jie-Ning Xiao Yun-Feng Chen Xiao-Ju Li Christian Staehelin Xue-Lin Huang 《Plant Growth Regulation》2008,54(2):165-177
Cotyledon segments derived from zygote embryos of mango (Mangifera indica L. cv. Zihua) were cultured on agar medium for 28 days. Depending on different pre-treatments with plant growth regulators,
two distinct patterns of adventitious roots were observed. A first pattern of adventitious roots was seen at the proximal
cut surface, whereas no roots were formed on the opposite, distal cut surface. The rooting ability depended on the segment
length and was significantly promoted by pre-treatment of embryos with indol-3-acetic acid (IAA) or indole-3-butyric acid
(IBA) for 1 h. A pre-treatment with the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) completely inhibited adventitious
root formation on proximal cut surfaces. A second pattern of roots was observed on abaxial surfaces of cotyledon segments
when embryos were pre-treated with 2,700 μM 1-naphthalenacetic acid (NAA) for 1 h. Histological observations indicated that
both patterns of adventitious roots originated from parenchymal cells, but developmental directions of the root primordia
were different. A polar auxin transport assay was used to demonstrate transport of [3H] indole-3-acetic acid (IAA) in cotyledon segments from the distal to the proximal cut surface. In conclusion, we suggest
that polar auxin transport plays a role in adventitious root formation at the proximal cut surface, whereas NAA levels (influx
by diffusion; carrier mediated efflux) seem to control development of adventitious roots on the abaxial surface of cotyledon
segments. 相似文献
13.
Takahashi H Kamada M Yamazaki Y Fujii N Higashitani A Aizawa S Yoshizaki I Kamigaichi S Mukai C Shimazu T Fukui K 《Planta》2000,210(3):515-518
Seedlings of most cucurbitaceous plants develop a peg (protuberance caused by cell outgrowth) on the transition zone between
the hypocotyl and root. The peg is necessary for removing the seed coat after germination. In our spaceflight experiments
on the STS-95 space shuttle, Discovery, we found that cucumber (Cucumis sativus L.) seedlings grown under microgravity conditions developed two pegs symmetrically at the transition zone. Thus, cucumber
seedlings potentially develop two pegs and do not require gravity for peg formation itself, but on the ground the development
of one peg is suppressed in response to gravity. This may be considered as negative control of morphogenesis by gravity.
Received: 17 August 1999 / Accepted: 4 October 1999 相似文献
14.
The effect of Tiron, a water soluble radical scavenger, on growth, morphology and alkaloid content of adventitious roots in Atropa belladonna 总被引:2,自引:0,他引:2
The effect of Tiron (disodium 1,2-dihydroxybenzene-3,5-disulfonate) on the growth, morphology and alkaloid content of adventitious
roots in Atropa belladonna was investigated. High concentrations of Tiron had an inhibitory effect on growth of the root. The appearance of cultured
roots was significantly changed from rough roots accompanied with callus-like tissue in control cultures to fine roots without
callus formation. Alkaloid content was drastically increased by the addition of 1 mM Tiron to the medium. The influence of
NAA, which has an inhibitory effect on alkaloid production, was partially restored by Tiron treatment, indicating that this
radical scavenger may affect the production of alkaloids through modulation of the mode of action of auxin. Glutathione content
of the root was not influenced by Tiron.
Received: 3 June 1999 / Revision received: 28 September 1999 / Accepted: 30 September 1999 相似文献
15.
Hieracium is a member of the Asteraceae family, and contains sexual species in addition to apomictic species that reproduce by apospory
and produce seed without fertilization. A homologue of the floral organ-identity gene DEFICIENS (DEF) was isolated from an apomictic line of Hieracium piloselloides (Vill.) following differential display between mature ovules and those initiating autonomous embryogenesis. The gene termed
HPDEF has 93% amino acid identity with GDEF2, a DEF homologue isolated from Gerbera hybrida (D. Yu et al., 1999, Plant J. 17: 51–62), another member of the Asteraceae. In-situ analysis showed that early in floral
development HPDEF is expressed in stamen and petal primordia, indicating expected B-function activity, according to the ABC model of floral
organ identity (J. L. Bowman et al., 1991, Development 112: 1–20; E. S. Coen and E. M. Meyerowitz, 1991, Nature 353: 31–37).
However, HPDEF expression was also observed in ovule primordia and expression continued in developing ovules until anthesis, indicating
that this gene may have a role in ovule development. Expression of HPDEF was not detected in megaspore mother cells, or in sexual or aposporous embryo sacs. In sexual Hieracium, HPDEF was uniformly expressed throughout the ovule integument until anthesis. In most ovules of the apomict, however, HPDEF expression was transiently down-regulated in a specific zone in the chalazal region where cells initiating aposporous embryo
sac formation differentiate. Uniform low-level HPDEF expression was subsequently observed prior to anthesis in ovules from sexual and apomictic plants. HPDEF may be down-regulated as a consequence of apomictic initiation and/or its down-regulation may facilitate progression of apomictic
events.
Received: 15 September 1999 / Accepted: 12 October 1999 相似文献
16.
Andreas Hamann 《Trees - Structure and Function》1998,12(3):175-180
Adventitious root formation in cuttings from fascicular shoots in loblolly pine (Pinus taeda L.) consists of four more or less discontinuous stages: (1) proliferation of cells at the base of the cutting, (2) differentiation
of wound vascular tissue and periderm, (3) dedifferentiation of a zone near the wound cambium and wound phloem to form a root
initial, and (4) formation of a root meristem. Anatomical changes during adventitious root initiation are described in cuttings
from donors of different types and ages. Cuttings from seedlings and 3- to 7-year-old hedged stock plants rooted better than
cuttings from 3-year-old tree form donors. It is concluded that the loss of rooting capacity in loblolly pine can be arrested
by shearing loblolly pine stock plants to low hedges. The process of root initiation, however, was similar in cuttings from
all sources and is apparently not the cause for the rapid decline of rooting potential with increasing age of the donor plant.
Received: 3 June 1997 / Accepted: 15 August 1997 相似文献
17.
Alfin1 transcription factor overexpression enhances plant root growth under normal and saline conditions and improves salt tolerance in alfalfa 总被引:11,自引:0,他引:11
Plant root development is an essential determinant of plant growth and crop yield that could be enhanced by induced changes in the expression of root-specific regulatory factors. We reported previously that Alfin1 binds DNA in a sequence-specific manner and that Alfin1 overexpression in transgenic alfalfa (Medicago sativa L.) enhances expression of the salt-inducible MsPRP2 gene in roots, suggesting that Alfin1 functions to regulate gene expression in roots. Here we show that Alfin1 is an essential gene for root growth and that its overexpression in transgenic plants confers a many-fold increase in root growth under normal and saline conditions. Alfin1-binding sites occur in promoters of genes expressed in roots of a wide variety of plant species and we propose that it is a general root growth regulator. Even though Alfin1 overexpression was under the control of the CaMV 35S promoter, plant shoot growth was not adversely affected. We show further that introduction of the Alfin1 transgene in plants confers a dominant characteristic that significantly increases plant growth and salt tolerance. 相似文献
18.
Inactivation of DNA replication origins by the cell cycle regulator, trigonelline, in root meristems of Lactuca sativa 总被引:4,自引:0,他引:4
The effects of trigonelline (TRG) on the cell cycle in root meristems of Lactuca sativa L. were examined in the knowledge that TRG is a cell cycle regulator that causes cell arrest in G2, and prevents ligation
of replicons in S-phase. The hypothesis was tested that continuous exposure to TRG would perturb DNA replication which, in
turn, would lengthen the cell cycle and impair root elongation. Using DNA fibre autoradiography, mean replicon size was 31
and 13 μm in the TRG (3 mM) and control treatments, respectively. Trigonelline also resulted in a lengthening of both S-phase
and the cell cycle and a decrease in primary root elongation. Hence, replicon inactivation was responsible for the protracted
S-phase. Trigonelline treatment also resulted in a 1.6-fold increase in fork rate (13.8 μm h−1) compared with the control (8.4 m h−1). The faster fork rate in the larger replicons is in accord with the highly significant positive relationship already established
between fork rate and replicon size for various unrelated higher plants.
Received: 11 October 1999 / Accepted: 23 December 1999 相似文献
19.
The entry of calcium and magnesium from external sources into mycorrhizal roots of 3-year-old Norway spruce trees (Piceaabies [L.] Karst.) was monitored. Roots of intact plants were exposed for various periods of time, ranging from 2 min to 48 h,
to nutrient solutions which contained the stable-isotope tracers 25Mg and 44Ca. After labelling, samples of roots were excised from the plants, shock-frozen, cryosubstituted and embedded. The resulting
isotope composition in this material was analysed by a laser-microprobe-mass-analyser (LAMMA) at relevant positions within
cross-sections of the roots. For both elements, we determined (i) the fractions of the isotopes originating from the plant
prior to labelling, and (ii) the fraction of isotopes originating from the corresponding tracer that penetrated into the root.
Both divalent cations rapidly penetrated across the cortical apoplast and reached the endodermis. After 2 min of exposure
to the labelling solution, an initial transient gradient of the tracers could be observed within the root cortex. Subsequently,
calcium as well as magnesium equilibrated between the apoplast of the entire cortex and the external tracer with a half-time,
t1/2, of about 3 min. In contrast, the kinetics of radial movement into the vascular stele showed a delay with a t1/2 of 100–120 min. We take this as strong evidence that there exists a free apoplastic path for divalent cations in the cortex
and that the endodermis is a major barrier to the further passage of Mg and Ca into the xylem. While 25Mg in the labelling solution exchanged rapidly with Mg in the cortical apoplast, the exchange across the plasma membrane with
Mg present in the protoplasm of the same cortical cells was almost 2 orders of magnitude slower. The kinetics of Ca and Mg
entry at +6 °C were similar to those obtained at a root temperature of +22 °C.
Received: 23 December 1998 / Accepted: 17 September 1999 相似文献
20.
The mechanical properties of young stems of Aristolochia macrophylla Lam. and Aristolochia brasiliensis Mart. et Zucc. were studied during elongation growth and primary differentiation. Data for the modulus of elasticity, for
the viscoelastic behaviour caused by longitudinal tension and for the shear modulus resulting from torsion around a longitudinal
axis were related to the underlying structural changes by quantitative analysis of stem anatomy, tissue distribution, ultrastructure,
and cell wall biochemistry. The orientation of cellulose microfibrils was determined by light microscopy and small-angle X-ray
diffraction, and the lignin content was determined by thioglycolic acid derivatization and spectroscopic quantification. It
was demonstrated that the increase in stability during early development is due to the complementary effects of increase in
cell wall material, lignification, and cellulose microfibril alignment. A detailed micromechanical model, considering internal
prestresses, is proposed to explain the characteristic biphasic stress-strain behaviour as well as the strain-hardening observed.
Received: 22 March 1999 / Accepted 9 September 1999 相似文献