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1.
The involvement of cell-wall polymer synthesis in auxin-mediated elongation of coleoptile segments from Zea mays L. was investigated with particular regard to the growth-limiting outer epidermis. There was no effect of indole acetic acid (IAA) on the incorporation of labeled glucose into the major polysaccharide wall fractions (cellulose, hemicellulose) within the first 2 h of IAA-induced growth. 2,6-Dichlorobenzonitrile inhibited cellulose synthesis strongly but had no effect on IAA-induced segment elongation even after a pretreatment period of 24 h, indicating that the growth response is independent of the apposition of new cellulose microfibrils at the epidermal cell wall. The incorporation of labeled leucine into total and cell-wall protein of the epidermis was promoted by IAA during the first 30 min of IAA-induced growth. Inhibition of IAA-induced growth by protein and RNA-synthesis inhibitors (cycloheximide, cordycepin) was accompanied by an inhibition of leucine incorporation into the epidermal cell wall during the first 30 min of induced growth but had no effect on the concomitant incorporation of monosaccharide precursors into the cellulose or hemicellulose fractions of this wall. It is concluded that at least one of the epidermal cell-wall proteins fulfills the criteria for a growth-limiting protein induced by IAA at the onset of the growth response. In contrast, the synthesis of the polysaccharide wall fractions cellulose and hemicellulose, as well as their transport and integration into the growing epidermal wall, appears to be independent of growth-limiting protein and these processes are therefore no part of the mechanism of growth control by IAA.Abbreviations CHI
cycloheximide
- COR
cordycepin
- DCB
2,6-dichlorobenzonitrile
- GLP
growth-limiting protein(s)
- IAA
indole-3-acetic acid 相似文献
2.
Four experimental predictions of the acid-growth theory of auxin (indole-3-acetic acid, IAA) action in inducing cell elongation were reinvestigated using abraded segments of maize (Zea mays L.) coleoptiles. i) Quantitative comparison of segment elongation and medium-acidification kinetics measured in the same sample of tissue reveals that these IAA-induced processes are neither correlated in time nor responding coordinately to cations present in the medium. ii) Exogenous protons are not able to substitute for IAA in causing segment elongation at the predicted pH of 4.5–5.0. Instead, external buffers induce significant segment elongation only below pH 4.5, reaching a maximal response at pH 1.75–2.5. Acid and IAA coact additively, and therefore independently, in the whole range of feasible pH values. iii) Neutral or alkaline buffers (pH 6–10) are unable to abolish the IAA-mediated growth response and have no effect on its lag-phase. iv) Fusicoccin, at a concentration producing the same H+ excretion as high concentrations of IAA, is ineffective in inducing segment elongation. Moreover, sucrose and other sugars can quantiatively substritute for IAA in inducing H+ excretion but are likewise ineffective in inducing elongation. It is concluded that these results are incompatible with the acid-growth theory of auxin action.Abbreviations IAA
indole-3-acetic acid
- FC
fusicoccin 相似文献
3.
Cell-wall tension of the inner tissues of the maize coleoptile and its potential contribution to auxin-mediated organ growth 总被引:1,自引:0,他引:1
Plant organs such as maize (Zea mays L.) coleoptiles are characterized by longitudinal tissue tension, i.e. bulk turgor pressure produces unequal amounts of cell-wall tension in the epidermis (essentially the outer epidermal wall) and in the inner tissues. The fractional amount of turgor borne by the epidermal wall of turgid maize coleoptile segments was indirectly estimated by determining the water potential * of an external medium which is needed to replace quantitatively the compressive force of the epidermal wall on the inner tissues. The fractional amount of turgor borne by the walls of the inner tissues was estimated from the difference between -* and the osmotic pressure of the cell sap (i) which was assumed to represent the turgor of the fully turgid tissue. In segments incubated in water for 1 h, -* was 6.1–6.5 bar at a i of 6.7 bar. Both -* and i decreased during auxin-induced growth because of water uptake, but did not deviate significantly from each other. It is concluded that the turgor fraction utilized for the elastic extension of the inner tissue walls is less than 1 bar, i.e. less than 15% of bulk turgor, and that more than 85% of bulk turgor is utilized for counteracting the high compressive force of the outer epidermal wall which, in this way, is enabled to mechanically control elongation growth of the organ. This situation is maintained during auxin-induced growth.Abbreviations and Symbols i
osmotic pressure of the tissue
- 0
external water potential
- *
water potential at which segment length does not change
- IAA
indole-3-acetic acid
- ITW
longitudinal inner tissue walls
- OEW
outer epidermal wall
- P
turgor
Supported by Deutsche Forschungsgemeinschaft (SFB 206). 相似文献
4.
J. Carrasco-Luna A. Calatayud F. González-Darós S. del Valle-Tascón 《Protoplasma》1995,184(1-4):63-71
Summary The influence of exogenous potassium hexacyanoferrate (III) (HCF III) on elongation of maize (Zea mays L.) coleoptile segments was investigated. Addition of HCF III led to a strong stimulation of growth both in the presence and absence of indole-3-acetic acid (IAA). The magnitude of growth stimulation was dependent on the presence of IAA, HCF III concentration, incubation time, and phase growth. The reduced form, potassium hexacyanoferrate (II), was without effect on growth. In the presence of HCF III, elongation was suppressed when coleoptile segments were treated with N,N-dicyclohexylcarbodiimide, cycloheximide or atebrine (quinacrine). The addition of HCF III stimulated the IAA-induced proton extrusion, and the e–/H+ ratio decreased with incubation time. HCF III also strongly stimulated elongation ofAvena saliva L. coleoptile segments andGlycine max L. hypocotyl segments. These results suggested that a plasma membrane redox system (NADH oxidase type I) may be involved in the regulation of growth through the activity of the plasma membrane-bound ATPase.Abbreviations CH
cycloheximide
- DCCD
N,N-dicyclohexylcarbodiimide
- HCF III
potassium hexacyanoferrate (III) (potassium ferricyanide)
- HCF II
potassium hexacyanoferrate (II) (potassium ferrocyanide)
- IAA
indole-3-acetic acid 相似文献
5.
6.
Microsomal vesicles prepared from etiolated hypocotyl tissue of zucchini (Cucurbita pepo L. cv. All Green Bush) exhibited saturable N-1-naphthylphthalamic acid ([3H]NPA) binding, NPA-stimulated association of indol-3yl-acetic acid ([3H]IAA), and saturable binding of guanosine 5-O-[3-thiotriphosphate] (GTP--[35S]). These vesicles were used to test the possibility that NPA receptors might interact with IAA-anion efflux carriers by coupling through a GTP-binding protein (G-protein). Unlabelled GTP--S or guanosine 5-O-[2-thiodiphosphate] (GDP--S) had no effect on saturable NPA binding or on the NPA-stimulated association of IAA with microsomes. NPA did not affect saturable binding of GTP--[35S] to microsomes, either in the presence or absence of saturating concentrations of unlabelled GTP--S or GDP. It is concluded that the occupancy of phytotropin receptors is not transduced to auxin efflux carriers by a GTP-binding protein. 相似文献
7.
Robert E. Cleland 《Planta》1984,160(6):514-520
The relationship between the plastic-extensibility values (PEx) obtained in the Instron technique and the growth parameter, wall extensibility () has been evaluated for Avena sativa L. coleoptile cell walls. The possibility that PEx is proportional to the growth rate rather than to has been eliminated by showing that turgor-driven changes in the growth rate do not cause comparable changes in PEx. For Avena coleoptiles, PEx appears to be a measure of the average over the previous 60–90 min rather than a measure of the instantaneous of the growth equation. This is indicated by the fact that while PEx and the growth rate start to change simultaneously after addition of indole-3-acetic acid or KCN, the growth rate reaches a new, constant value 60–90 min before a new plateau value of PEx is obtained. Similar results are obrained with soybean (Glycine max L.) hypocotyl walls, indicating that the relationship between PEx and the parameter is a general one, although the period over which is averaged differs from tissue to tissue. In addition, it is shown that PEx can be measured more than once on the same section; a new potential for plastic extension is regenerated whenever the force vectors are changed even slightly. It is concluded that PEx is a measure of those domains in the wall where a wall-loosening event has occurred which has not been eliminated by further wall synthesis or other biochemical events.Abbreviations and symbols DP
Instron plastic compliance
- IAA
indole-3-acetic acid
- PEx
Instron plastic extensibility
-
instantaneous wall extensibility 相似文献
8.
Incorporation and release of 14C-label in prenylquinones of Chlorella was investigated under steady state conditions. After one hour of 14CO2-photosynthesis all plastid quinones investigated were labeled. The highest label was found in phylloquinone (18%) while -tocopherol exhibits the lowest label (0.38%). Among the plastoquinones, plastohydroquinone-9 shows a higher labeling degree (5.1%) and a faster labeling kinetic than plastoquinone-9 (1.6%). After replacement of 14CO2 against 12CO2 the total radioactivity in plastohydroquinone-9, -tocopherol and phylloquinone decreases but in -tocoquinone and plastoquinone-9 proceeds further. From this labeling kinetic we conclude, that newly synthesized [14C]-tocopherol molecules are converted to [14C]-tocoquinone and [14C]plastohydroquinone-9 molecules to [14C]plastoquinone-9. From their 14C-incorporation kinetic half-lives could be calculated for all prenylquinones in the same ranges as previously found for the chlorophylls and carotenoids (Grumbach et al., 1978). Half-lives are shorter in plastohydroquinone-9 (30 min) and plastoquinone-9 (40 min) than in phylloquinone (55 min), -tocoquinone (50 min) and -tocopherol (220 min). This means that all prenyl-lipids such as chlorophyll a, -and -carotene, plastohydroquinone-9 and plastoquinone-9 which are more directly involved in the process of photosynthesis are subject to a continuous and higher turnover than the xanthophyll and -tocopherol. From the fast labeling kinetic and short half-lives of -tocoquinone and especially phylloquinone with a labeling degree of 12% after one hour of 14CO2 photosynthesis we suppose that perhaps these two prenylquinones are also involved in the photosynthetic activity of chloroplasts. 相似文献
9.
Treatment of etiolated zucchini (Cucurbita pepo L.) hypocotyl tissue with sub-micromolar concentrations of the cationophore monensin rapidly (<20 min) inhibited the transport catalytic activity of the specific auxin-anion efflux carrier and reduced the inhibition of this carrier by the phytotropin N-1-naphthylphthalamic acid (NPA). Monensin inhibited the basipetal polar transport of indol-3yl-acetic acid (IAA) in long (30 mm) zucchini segments. At concentrations lower than 10–5 mol·dm–3 monensin did not affect uptake of the pH probe [2-14C]5,5-dimethyloxazolidine-2,4-dione (DMO) or that of the membrane-potential probe tetra[14C-phenyl]phosphonium bromide (TPP+), did not affect the response of IAA net uptake to external Ca2+ concentration and did not alter the metabolism of IAA. It was concluded that low concentrations of monensin inhibit transport through the Golgi apparatus of auxin efflux carrier protein and that the efflux carriers turn over very rapidly in the plasma membrane. Monensin pretreatment did not affect the saturable binding of [3H]NPA to microsomal membranes, indicating that the auxin-efflux catalytic sites and the NPA-binding sites are located on separate proteins. At higher concentrations (10–5 mol·dm–3) monensin inhibited both mediated uptake and mediated efflux components of IAA transport. This effect was at least in part attributable to perturbation by monensin of the driving forces for mediated uptake since high concentrations of monensin also reduced the uptake of DMO and TPP+.Abbreviations CH
cycloheximide
- DMO
5,5-dimethyloxazolidine-2,4-dione
- MDMP
2-(4-methyl-2,6-dinitroanlilino)N-methyl-propionamide
- NPA
N-1-naphthylphthalamic acid
- TPP+
tetraphenylphosphonium ion
We thank Mrs. R.P. Bell for technical assistance and Drs. G.F. Katekar and M.A. Venis for generous gifts of NPA. S.W. was supported by the U.K. Science and Engineering Research Council. 相似文献
10.
The function of the epidermis in auxinmediated elongation growth of maize (Zea mays L.) coleoptile segments was investigated. The following results were obtained: i) In the intact organ, there is a strong tissue tension produced by the expanding force of the inner tissues which is balanced by the contracting force of the outer epidermal wall. The compression imposed by the stretched outer epidermal wall upon the inner tissues gives rise to a wall-pressure difference which can be transformed into a water-potential difference between inner tissues and external medium (water) by removal of the outer epidermal wall. ii) Peeled segments fail to respond to auxin with normal growth. The plastic extensibility of the inner-tissue cell walls (measured with a constant-load extensiometer using living segments) is not influenced by auxin (or abscisic acid) in peeled or nonpeeled segments. It is concluded that auxin induces (and abscisic acid inhibits) elongation of the intact segment by increasing (decreasing) the extensibility specifically in the outer epidermal wall. In addition, tissue tension (and therewith the pressure acting on the outer epidermal wall) is maintained at a constant level over several hours of auxin-mediated growth, indicating that the inner cells also contribute actively to organ elongation. However, this contribution does not involve an increase of cell-wall extensibility, but a continuous shifting of the potential extension threshold (i.e., the length to which the inner tissues would extend by water uptake after peeling) ahead of the actual segment length. Thus, steady growth involves the coordinated action of wall loosening in the epidermis and regeneration of tissue tension by the inner tissues. iii) Electron micrographs show the accumulation of striking osmiophilic material (particles of approx. 0.3 m diameter) specifically at the plasma membrane/cell-wall interface of the outer epidermal wall of auxin-treated segments. iv) Peeled segments fail to respond to auxin with proton excretion. This is in contrast to fusicoccin-induced proton excretion and growth which can also be readily demonstrated in the absence of the epidermis. However, peeled and nonpeeled segments show the same sensitivity to protons with regard to the induction of acid-mediated in-vivo elongation and cell-wall extensibility. The observed threshold at pH 4.5–5.0 is too low to be compatible with a second messenger function of protons also in the growth response of the inner tissues. Organ growth is described in terms of a physical model which takes into account tissue tension and extensibility of the outer epidermal wall as the decisive growth parameters. This model states that the wall pressure increment, produced by tissue tension in the outer epidermal wall, rather than the pressure acting on the inner-tissue walls, is the driving force of growth.Abbreviations and symbols
E
el, E
pl
elastic and plastic in-vitro cell-wall extensibility, respectively
-
E
tot
E
el+E
pl
- FC
fusicoccin
- IAA
indole-3-acetic acid
- IT
inner tissue
- ITW
inner-tissue walls
- OEW
outer epidermal wall
-
osmotic pressure
-
P
wall pressure
-
water potential 相似文献
11.
Three predictions of the acid-growth theory of fusicoccin (FC) action in inducing cell elongation were reinvestigated using abraded segments of maize (Zea mays L.) coleoptiles. i) Quantitative comparison of segment elongation and medium-acidification kinetics measured in the same sample of tissue shows that these FC-induced processes are strictly correlated in time and respond coordinately to cations present in the medium. ii) Fusicoccin (1 mol l-1) induces a rapid acidification of the cell-wall solution, reaching a final level of pH 3.8–4.0. Exogenous protons are able to substitute quantitatively for FC in causing segment elongation at pH 3.8–4.0. At pH 4, FC has no additional effect on cell elongation. iii) Neutral buffers (pH 7) completely abolish the FC-mediated growth response. iv) Cycloheximide (10 mg l-1) inhibits both FC-induced and acid-buffer(pH 4)-induced elongation after a lag of 40–45 min, and FC-induced H+ excretion after a lag of 2 h. Under the same conditions, indole-3-acetic acid-induced elongation and H+ excretion are inhibited without detectable lag. It is concluded that these results are fully compatible with the acid-growth theory of FC action.Abbreviations IAA
indole-3-acetic acid
- CHI
cycloheximide
- FC
fusicoccin 相似文献
12.
To study the effect of auxin on direct somatic embryogenesis from leaf cultures ofOncidium `Gower Ramsey', 1-cm-long explants have been cultured in vitro testing IAA, 2,4-, quercetin, TIBA and PCIB. On a modified MS medium devoid of plant growth regulators, leaf cells of three regions (leaf tips, adaxial sides and cut ends) formed somatic embryos. After 8 weeks in culture, the frequencies of embryo-forming explants were 55, 52.5 and 30 % on leaf tips, adaxial sides and cut ends, respectively, and the numbers of embryos per dish was 89.3. Except for TIBA, other growth regulators (IAA, 2,4-, quercetin, PCIB) and their combinations tested, all retarded direct embryo formation. In the presence of 0.1 and 0.5 M TIBA, leaf tip, adaxial sides and cuts end of explants gave almost the same embryogenic response as the control. However, 10 and 27.5 % of explants were induced to form embryos from abaxial sides, and these explants did not form embryos on cut ends. In addition, after 8weeks in culture, TIBA at 0.5M highly promoted the mean numbers of embryos per dish to 134.2. 相似文献
13.
An improved method is introduced for the determination of the quantum yield of photosystem I. The new method employs saturating light pulses with steep rise characteristics to distinguish, in a given physiological state, centers with an open acceptor side from centers with a reduced acceptor side. The latter do not contribute to PSI quantum yield (I). Oxidation of P700 is measured by a rapid modulation technique using the absorbance change around 830 nm. The quantum yield I is calculated from the amplitude of the rapid phase of absorbance change (A; 830 nm) upon application of a saturation pulse in a given state, divided by the maximal A (830 nm) which is induced by a saturation pulse with far-red background illumination. Using this technique, I can be determined even under conditions of acceptor-side limitation, as for example in the course of a dark-light induction period or after elimination of CO2 from the gas stream. Thus determined I values display a close-to-linear relationship with those for the quantum yield of PSII (II) calculated from chlorophyll fluorescence parameters. It is concluded that the proposed method may provide new information on the activity of the PSI acceptor side and thus help to separate the effects of acceptorside limitation from those of cyclic PSI, whenever a non-linear relationship between II and the P700-reduction level is observed.Abbreviations and Symbols A
absorbance change
- I
quantum yield of photosystem I
- II
quantum yield of photosystem II
- PAR
photosynthetically active radiation
This work was supported by the Deutsche Forschungsgemeinschaft (SFB 176 Molekulare Grundlagen der Signalübertragung und des Stofftransportes in Membranen and SFB 251 Ökologie, Physiologie und Biochemie pflanzlicher Leistung unter Streß). 相似文献
14.
Phenylacetic acid (PAA), a naturally-occurring acidic plant growth substance, was readily taken up by pea (Pisum sativum L. cv. Alderman) stem segments from buffered external solutions by a pH-dependent, non-mediated diffusion. Net uptake from a 0.2 M solution at pH 4.5 proceeded at a constant rate for at least 60 min and, up to approx. 100 M, the rate of uptake was directly proportional to the external concentration of the compound. The net rate of uptake of PAA was not affected by the inclusion of indol-3yl-acetic acid (IAA) in the uptake medium (up to approx. 30 M) and, unlike the net uptake of IAA, was not stimulated by N-1-naphthylphthalamic acid (NPA) or 2,3,5-triiodobenzoic acid. At an external concentration of 0.2 M and pH 4.5, the net rate of uptake of PAA was about twice that of IAA. It was concluded that the uptake of PAA did not involve the participation of carriers and that PAA was not a transported substrate for the carriers involved in the uptake and polar transport of IAA. Nevertheless, the inclusion of 3–100 M unlabelled PAA in the external medium greatly stimulated the uptake by pea stem segments of [1-14C]IAA (external concentration 0.2 M). It was concluded that whilst PAA was not a transported substrate for the NPA-sensitive IAA efflux carrier, it interacted with this carrier to inhibit IAA efflux from cells. Over the concentration range 3–100 M, PAA progressively reduced the stimulatory effect of NPA on IAA uptake, indicating that PAA also inhibited carrier-mediated uptake of IAA. The consequences of these observations for the regulation of polar auxin transport are discussed.Abbreviations IAA
indol-3yl-acetic acid
- DMO
5,5-dimethyloxazolidine-2,4-dione
- NPA
N-1-naphthylphthalamic acid
- PAA
phenylacetic acid
- TIBA
2,3,5-triiodobenzoic acid 相似文献
15.
Inhibitory action of red light on the growth of the maize mesocotyl: evaluation of the auxin hypothesis 总被引:8,自引:0,他引:8
Moritoshi Iino 《Planta》1982,156(5):388-395
Brief irradiation of 3-d-old maize (Zea mays L.) seedlings with red light (R; 180 J m-2) inhibits elongation of the mesocotyl (70–80% inhibition in 8 h) and reduces its indole-3-acetic acid (IAA) content. The reduction in IAA content, apparent within a few hours, is the result of a reduction in the supply of IAA from the coleoptile unit (which includes the shoot apex and primary leaves). The fluence-response relationship for the inhibition of mesocotyl growth by R and far-red light closely resemble those for the reduction of the IAA supply from the coleoptile. The relationship between the concentration of IAA (1–10 M) supplied to the cut surface of the mesocotyl of seedlings with their coleoptile removed and the growth increment of the mesocotyl, measured after 4 h, is linear. The hypothesis that R inhibits mesocotyl growth mainly by reducing the IAA supply from the coleoptile is supported. However, mesocotyl growth in seedlings from which the coleoptiles have been removed is also inhibited by R (about 25% inhibition in 8 h). This inhibition is not related to changes in the IAA level, and not relieved by applied IAA. In intact seedlings, this effect may also participate in the inhibition of mesocotyl growth by R. Inhibition of cell division by R, whose mechanism is not known, will also result in reduced mesocotyl elongation especially in the long term (e.g. 24 h).Abbreviations FR
far-red light
- IAA
indole-3-acetic acid
- Pfr
phytochrome in the far-red-absorbing form
- Pr
phytochrome in the red-absorbing form
- R
red light 相似文献
16.
The effect of plant growth regulators on the secondary wall thickeningof cotton fibre was studied. The results indicated that the GAS andiP+iPA levels in the fibre of field-grown cotton plantsremained almost constant but the IAA and ABA levels changed considerably duringfibre development. Although the change in both IAA and ABA levels seemed not tobe closely related with the rate of cellulose accumulation, there was still arelationship between the ratio of ABA to IAA and secondary wall thickening. Inin vitro studies, ABA (50mol·L–1) markedly enhanced theaccumulation of dry matter and cellulose in the fibre cell wall duringsecondarywall thickening, but no similar effect was observed with NAA, GA3 orkinetin treatments. The role of ABA in secondary wall thickening of cottonfibreis discussed. 相似文献
17.
Scots pine (Pinus sylvestris L.) seedlings grown in nutrient solution in controlled-environment chambers were used. The effects of a shortday (SD, early autumn) treatment on growth and the content of free and alkaline hydrolysable abscisic acid (ABA) in shoots and roots were investigated. The weekly relative growth rates of seedlings grown continuously under long-day (LD, summer) conditions were stable at approx. 0.08 g g–1 d–1 between weeks four and eight from germination. Weekly relative growth rates of seedlings transferred to SD conditions decreased rapidly to a then stable level of approx. 0.04 g g–1 d01. Shoot elongation ceased within two weeks of SD treatment. The content of both free and alkaline hydrolysable ABA was approx. 40–50% higher in shoots of seedlings grown for five weeks in LD plus one week in SD than in shoots of seedlings grown for five or six weeks in LD. Two additional weeks of SD did not change the free ABA content. Three weeks in simulated late autumn (SD but decreased temperatures) and three weeks in simulated winter (lower light intensity and temperature) further increased the content of free ABA in the shoots. A transfer back to LD conditions reduced the ABA content to a level equal to the level found during the first LD period. The recovery of radioactive ABA at certain times after application ofr[3H] ABA was the same in shoots and roots of LD-grown and SD-treated seedlings.Abbreviations ABA
abscisic acid
- LD
long day(s)
- RGR7
weekly relative growth rates
- SD
short day(s) 相似文献
18.
The relationship between steady-state elongation rate (G) and turgor pressure (P; G/P curve) was investigated using isolated segments of maize (Zea mays L.) coleoptiles incubated in osmotic solutions of a water potential range of 0 to -10 bar (polyethylene glycol 6000 as osmoticum). Short-term elongation measurements revealed curvilinear G/P curves with a steep slope at high turgor and a shallow slope at low turgor. Owing to a decrease of osmotic pressure and turgor, there was a tendency for straightening of the G/P curves during long-term elongation. An elongation rate of zero was adjusted by lowering the turgor by 4.5 bar at a constant osmotic pressure of 6.7 bar. Auxin increased — whereas abscisic acid decreased — the slope of the G/P curve but these hormones had no effect on the threshold turgor of growth (Y = 2.2 bar). It is concluded that extensibility of the growing cell walls represented by the yielding coefficient of Lockhart's growth equation is turgor-dependent and therefore decreases to a very low value as the turgor approaches Y. When the turgor was kept at Y, a constant segment length was maintained over at least 6 h. However, separation of reversible (lrev) and irreversible (lirr) components of total (in vivo) length (ltot = lrev + lirr) W measuring segment length before and after freezing/thawing revealed that lirr increased continuously and lrev decreased continuously at constant ltot. After a step-down in turgor the segments grew in lirr although they shrank in ltot over the whole turgor range of 0
irr irreversible length - lrev reversible length - ltot total length (= lirr + lrev) - i osmotic pressure of cell sap - i water potential of tissue - o water potential of incubation medium - ABA abscisic acid - G growth rate - m yielding coefficient - P turgor pressure - PEG polyethylene glycol 6000 - Y yield threshold Supported by Deutsche Forschungsgemeinschaft (SFB 206). We thank R. Hertel for helpful comments. 相似文献
19.
F. Pupilli S. Arcioni F. Damiani M. Pezzotti 《Plant Cell, Tissue and Organ Culture》1990,23(3):193-199
Plant regeneration from leaf- and cotyledon-derived calli and from protoplast-derived tissue has been obtained in Lotus pedunculatus. Callus induction was achieved with 2,4-D and plant regeneration required the following two media sequences: bud formation was stimulated by IAA and BA and shoot growth by kinetin. Root formation occurred in the presence of IAA. Cotyledon protoplasts showed a low plating efficiency and plant regeneration was achieved via an intervening callus phase.Abbreviations BA
6-benzyladenine
- 2,4-D
2,4-dichlorophenoxyacetic acid
- IAA
indole-3-acetic acid
- IBA
indole-3-butyric acid
- 2iP
N6--2-isopentenyl-adenine
- NAA
-naphthaleneacetic acid 相似文献
20.
Thirty five strains of Arabidopsis thaliana (L.) Heynh. have been identified with altered phototropic responses to 450-nm light. Four of these mutants have been more thoroughly characterized. Strain JK224 shows normal gravitropism and second positive phototropism. However, while the amplitude for first positive phototropism is the same as that in the wild-type, the threshold and fluence for the maximum response in first positive phototropism are shifted to higher fluence by a factor of 20–30. This mutant may represent an alteration in the photoreceptor pigment for phototropism. Strain JK218 exhibits no curvature to light at any fluence from 1 mol·m-2 to 2700 mol·m-2, but shows normal gravitropism. Strain JK345 shows no first positive phototropism, and reduced gravitropism and second positive phototropism. Strain JK229 shows no measurable first positive phototropism, but normal gravitropism and second positive phototropism. Based on these data, it is suggested that: 1. gravitropism and phototropism contain at least one common element; 2. first positive and second positive phototropism contain at least one common element; and 3. first positive phototropism can be substantially altered without any apparent alteration of second positive phototropism.Abbreviation WT
wild-type 相似文献