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1.
Effect of Putrescine, 4-PU-30, and Abscisic Acid on Maize Plants Grown under Normal, Drought, and Rewatering Conditions 总被引:7,自引:0,他引:7
The experiments were carried out with maize (Zea mays L.) seedlings, hybrid Kneja 530, grown hydroponically in a growth chamber. Twelve-day-old plants were foliar treated with
putrescine, N1-(2-chloro-4-pyridyl)-N2-phenylurea (4-PU-30), and abscisic acid (ABA) at concentrations of 10−5
m. Twenty-four hours later the plants were subjected to a water deficit program, induced by 15% polyethylene glycol (PEG; molecular
weight, 6,000). Three days after drought stress half of the plants were transferred to nutrient solution for the next 3 days.
The effects of the water shortage, rewatering, and plant growth regulator (PGR) treatment on the fresh and dry weights, leaf
pigment content, proline level, relative water content (RWC), transpiration rate, activities of catalase and guaiacol peroxidase,
hydrogen peroxide content, and level of the products of lipid peroxidation were studied. It was established that the application
of PGRs alleviated to some extent the plant damage provoked by PEG stress. At the end of the water shortage program the plants
treated with these PGRs possessed higher fresh weight than drought-subjected control seedlings. It was found also that putrescine
increased the dry weight of plants. Under drought, the RWC and transpiration rate of seedlings declined, but PGR treatment
reduced these effects. The accumulation of free proline, malondialdehyde, and hydrogen peroxide was prevented in PGR-treated
plants compared with the water stress control. The results provided further information about the influence of putrescine,
4-PU-30, and ABA on maize plants grown under normal, drought, and rewatering conditions.
Received September 25, 1997; accepted August 10, 1998 相似文献
2.
J. Beltrano M. G. Ronco E. R. Montaldi A. Carbone 《Journal of Plant Growth Regulation》1998,17(1):53-57
Treatment of flag leaves and ears of wheat plants with MJ (jasmonic acid methylester) (10−5 and 10−4
m) did not increase ethylene production, but it did accelerate senescence as indicated by the loss of chlorophyll. MJ also
caused the closure of stomata, and consequently the rates of transpiration and photosynthesis decreased. Early maturity shortened
the grain filling period, so the thousand grain weight was lower. Although ethylene elicited the same physiologic effects,
the syndrome of senescence by MJ is independent of the former. We conclude that senescence and death in wheat are far from
being elucidated; however, MJ and ethylene seem to participate in the phenomenon.
Received July 10, 1997; accepted January 5, 1998 相似文献
3.
Physiologic and Yield Responses of Shaded Cotton to the Plant Growth Regulator PGR-IV 总被引:2,自引:0,他引:2
The plant growth regulator PGR-IV has been reported to improve the growth, boll retention, and yield of cotton (Gossypium hirsutum L.) under optimum growing conditions. However, little is known about the response of cotton to PGR-IV under low light stress.
A 3-year field study was conducted to determine if applying PGR-IV before an 8-day period of shade (63% light reduction) benefitted
the growth and yield of shaded cotton. Shading during early squaring did not affect yield. Shading after the first flower
stage significantly increased leaf chlorophyll concentration and fruit abscission and decreased the leaf photosynthetic rate,
nonstructural carbohydrate concentrations, and lint yield. Foliar application of PGR-IV at 292 mL ha−1 at early squaring and first flower did not improve the leaf photosynthetic rate of shaded cotton. However, shaded plants
receiving PGR-IV had higher nonstructural carbohydrate concentrations in the floral buds and significantly lower fruit abscission
than the shaded plants without PGR-IV. Applying PGR-IV to the foliage before shading resulted in a numeric increase (6–18%)
in lint yield compared with shaded plants without PGR-IV. The decreased fruit abscission from the application of PGR-IV was
associated with improved assimilate translocation. The yield enhancement from foliar application of PGR-IV was attributed
to increased fruit retention. However, the average boll weight of shaded plants with PGR-IV tended to be lower than that of
shaded plants without PGR-IV. Lint percentage was not affected by PGR-IV. Foliar application of PGR-IV appears beneficial
for increasing the fruit retention of shaded cotton.
Received June 12, 1997; accepted January 19, 1998 相似文献
4.
L. S. Nelson 《Journal of Plant Growth Regulation》1996,15(1):33-38
Studies were conducted in 55-liter aquariums under controlled environment conditions to evaluate growth regulator effects of flurprimidol [-(1-methylethyl)--[4-(trifluoromethoxy) phenyl]-5-pyrimidinemethanol] on Eurasian watermilfoil (Myriophyllum spicatum L.). Treatments included flurprimidol concentrations ranging from 0 to 500 g L-1, with exposure times varying from 0.25 to 28 days. Extending the flurprimidol contact time increased the growth inhibitory response. Flurprimidol-treated shoots were 14–64% shorter than untreated plants at 14 DAT (days after treatment). Growth inhibition persisted 56 DAT for plants exposed to 25 and 100 g L-1 flurprimidol for 28 days or 200 g L-1 flurprimidol for 10 days. Growth-inhibited plants accumulated starch in shoots and roots, whereas plants showing little or no growth suppression utilized available assimilate for growth. Treatments that most effectively suppressed shoot length accumulated up to 68% more total nonstructural carbohydrate compared with untreated plants. Shoot and root dry weight biomass were unaffected by flurprimidol.Abbreviations PGR(s)
plant growth regulator(s)
- TNC
total non-structural carbohydrate
- DAT
days after treatment
- PVC
polyvinyl chloride
- DW
dry weight
- BOD
biological oxygen demand
- DMSO
dimethyl sulfoxide
- LSD
least significant difference 相似文献
5.
M. J. Montague 《Journal of Plant Growth Regulation》1997,16(1):11-19
Segments can be cut from the peducular-1 internode of oat (Avena sativa L.) shoots so as to contain the graviresponsive, auxin-sensitive leaf sheath pulvinus, and the gibberellin-sensitive internodal
tissue. These two growth-capable tissues were used to study the effects and interactions of jasmonic acid (JA) and abscisic
acid (ABA) in regulating cell elongation. When supplied alone at physiologic concentrations (10−5, 10−4
m), JA promoted growth and cell wall synthesis in the internodal tissue, whereas by itself, ABA inhibited internodal elongation
and even inhibited JA-promoted growth. When gibberellic acid (GA3) was used to stimulate internodal elongation, JA and ABA caused similar levels of inhibition and, at certain concentrations,
were synergistic. Inhibition by ABA was initiated several hours earlier than inhibition by JA, and only the ABA effect could
be partially overcome by 10−3
m aminoethoxyvinylglycine. Both JA and ABA inhibited elongation of pulvinar tissue that was induced to grow by gravistimulus
or auxin, although here JA was more potent than ABA at equimolar concentrations. When 10−5
m fusicoccin was used as a general nonphysiologic growth stimulus, JA had no effect on the internode but inhibited the pulvinus,
whereas ABA had no effect on the pulvinus but inhibited the internode. These results provide strong physiologic evidence that
JA and ABA act by different mechanisms in the regulation of elongation, at least in this representative grass.
Received May 28, 1996; accepted November 7, 1996 相似文献
6.
The effect of brassinolide (BR) on cell growth and shikonin and its derivative formation in Onosma paniculatum cell culture was studied. BR addition with IAA and BAP (+BR/+IAA/+BAP) in B5 medium slightly increased the cell growth at 0.01–0.1 ppb concentration compared with a growth control (−BR/+IAA/+BAP). Only
BR addition (+BR/−IAA/−BAP) at 0.001–100 ppb in B5 medium significantly increased the cell fresh weight compared with a growth control (−BR/−IAA/−BAP). The same concentration
of BR tested at 0–1000 ppb increased the cell fresh weight of +IAA/+BAP significantly more than that of −IAA/−BAP. BR at 0.001–0.1
ppb with IAA and BAP added (+BR/+IAA/+BAP) in M9 medium increased shikonin and its derivative content markedly by 31–87%, compared with its control (−BR/+IAA/+BAP). BR at
0.001–1000 ppb without IAA and BAP added to M9 medium (+BR/−IAA/−BAP) also increased shikonin and its derivative content compared with its control (−BR/−IAA/−BAP). However,
the amount of shikonin and derivative formed of +IAA/+BAP was greater than that of −IAA/−BAP only at the same concentration
of BR at 0–1 ppb. These combined results show that BR at 0.01 ppb with IAA and BAP added was the best for cell growth and
shikonin formation. Formation of shikonin and its derivative by adding BR at 0.01 ppb with IAA and BAP (+BR/+IAA/+BAP) in
M9 medium was significantly enhanced 4 days after BR addition compared with a production control (−BR/+IAA/+BAP). In contrast,
+BR/−IAA/−BAP vs. −BR/−IAA/−BAP was not as effective as +BR/+IAA/+BAP vs. −BR/+IAA/+BAP for the shikonin formation. The time
course study for shikonin formation also showed that +BR/+IAA/+BAP and −BP/+IAA/+BAP only slightly increased cell growth in
M9 medium. Similarly, soluble protein content in the cells treated by BR at 0.01 ppb with IAA and BAP (+BR/+IAA/+BAP) exceeded
that of the control (−BR/+IAA/+BAP) 4 days after BR addition. And +BR/−IAA/−BAP only slightly increased the soluble protein
content over that of −BR/−IAA/−BAP.
Received November 2, 1998; accepted August 25, 1999 相似文献
7.
Foliar applications of the plant growth regulators (PGRs) flurprimidol and mefluidide suppressed shoot elongation and regrowth and enhanced shoot injury caused by selected herbicides in Canada thistle (Cirsium arvense L.). Flurprimidol stimulated movement of 14C-sucrose from leaves to roots. However, the stimulation was nullified when glyphosate, chlorsulfuron, or clopyralid was applied to foliage 1 week after application of the PGR. Herbicide-induced root injury was not enhanced by PGR application but these PGRs may be useful in decreasing weed competition among crops not similarly inhibited. 相似文献
8.
New Plant Growth Regulators Protect Photosynthesis and Enhance Growth Under Drought of Jack Pine Seedlings 总被引:12,自引:0,他引:12
To determine whether natural plant growth regulators (PGRs) can enhance drought tolerance and the competitive ability of
transplanted seedlings, 1.5-year-old jack pine (Pinus banksana Lamb.) seedlings were treated with homobrassinolide, salicylic acid, and two polyamines, spermine and spermidine, triacontanol,
abscisic acid (ABA), and the synthetic antioxidant, Ambiol. PGRs were fed into the xylem for 7 days and plants were droughted
by withholding water for 12 days. ABA, Ambiol, spermidine, and spermine at a concentration of 10 μg L−1 stimulated elongation growth under drought, whereas ABA, Ambiol, and spermidine maintained higher photosynthetic rates, higher
water use efficiency, and lower Ci/Ca ratio under drought compared with control plants. The damaging effects of drought on
membrane leakage was reversed by Ambiol, ABA, triacontanol, spermidine, and spermine. Because ABA, Ambiol, and both polyamines
enhanced elongation growth and also reduced membrane damage in jack pine under drought, they show promise as treatments to
harden seedlings against environmental stress. The protective action of these compounds on membrane integrity was associated
with an inhibition of ethylene evolution, with a reduction in transpiration rate and an enhancement of photosynthesis, which
together increased water use efficiency under drought. Although most of the tested compounds acted as antitranspirants, the
inhibition in membrane leakage in ABA-, Ambiol-, and polyamine-treated plants appeared more closely related to the antiethylene
action.
Received December 30, 1998; accepted October 14, 1999 相似文献
9.
Ganka Chaneva Sevdalina Furnadzhieva Kaledona Minkova Jaromir Lukavsky 《Journal of applied phycology》2007,19(5):537-544
The effect of light intensity (50–300 μmol photons m−2 s−1) and temperature (15–50°C) on chlorophyll a, carotenoid and phycobiliprotein content in Arthronema africanum biomass was studied. Maximum growth rate was measured at 300 μmol photons m−2 s−1 and 36°C after 96 h of cultivation. The chlorophyll a content increased along with the increase in light intensity and temperature and reached 2.4% of dry weight at 150 μmol photons
m−2 s−1 and 36°C, but it decreased at higher temperatures. The level of carotenoids did not change significantly under temperature
changes at illumination of 50 and 100 μmol photons m−2 s−1. Carotenoids were about 1% of the dry weight at higher light intensities: 150 and 300 μmol photons m−2 s−1. Arthronema africanum contained C-phycocyanin and allophycocyanin but no phycoerythrin. The total phycobiliprotein content was extremely high,
more than 30% of the dry algal biomass, thus the cyanobacterium could be deemed an alternative producer of C-phycocyanin.
A highest total of phycobiliproteins was reached at light intensity of 150 μmol photons m−2 s−1 and temperature of 36°C, C-phycocyanin and allophycocyanin amounting, respectively, to 23% and 12% of the dry algal biomass.
Extremely low (<15°C) and high temperatures (>47°C) decreased phycobiliprotein content regardless of light intensity. 相似文献
10.
Survival of conifer transplants is often poor on exposed planting sites in the boreal forest. More than one-third of all
conifers do not become established. To enhance the competitive ability of jack pine seedlings, seeds were treated with natural
plant growth regulators (PGRs; viz., homobrassinolide, salicylic acid, and two polyamines, spermine and spermidine) and growth
promotion was studied for 16 days. Homobrassinolide (5 ng l–1), salicylic acid (100 μg l–1) and spermine (10 μg l–1) enhanced elongation growth and elongation rate of whole plant. Homobrassinolide (5 ng l–1) and salicylic acid (100 μg l–1) stimulated root elongation by 38% and 10% respectively while spermine (1000 μg l–1) increased needle growth by 14%. Homobrassinolide stimulated dry weight growth and growth rate. Homobrassinolide recorded
over 20% increase in dry matter production, apportioned equally to root and needles, whereas spermine enhanced total dry matter
production by almost 10%, mostly by increasing needle weight. Homobrassinolide facilitated nearly 19% increase in growth rate
while spermine recorded only a 7% growth promotion. Spermidine inhibited both elongation and dry weight growth at all concentrations.
Growth promotion by homobrassinolide, salicylic acid and spermine may be through an acceleration of processes connected to
cell elongation, cell division and C allocation and these PGRs showed most promise for the early invigoration and improvement
of jack pine seedling growth.
Received: 27 August 1997 / Accepted: 8 January 1998 相似文献
11.
The effect of short-term exposure to elevated CO2 concentration and high irradiance on the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases
(GPX) and catalase (CAT), and on the extent of the lipid peroxidation was studied in bean (Phaseolus vulgaris L.) plants. Plants were exposed for 4 d (8 h a day) to irradiance of 100 (LI) or 1000 (HI) μmol m−2 s−1 at ambient (CA, 350 μmol mol−1) or elevated (CE, 1300 μmol mol−1) CO2 concentration. Four-day exposure to CE increased the leaf dry mass in HI plants and RuBPC activity and chlorophyll content
in LI plants. Total soluble protein content, leaf dry matter and RuBPC activity were higher in HI than in LI plants, although
the HI and CE increased the contents of malonyldialdehyde and H2O2. Under CA, exposure to HI increased the activity of APX and decreased the total SOD activity. Under CE, HI treatment also
activated APX and led to reduction of both, SOD and GPX, enzymes activities. CE considerably reduced the CAT activity at both
irradiances, possibly due to suppressed rate of photorespiration under CE conditions. 相似文献
12.
This paper studies the influence of the 7-oxalactone type of brassinosteroids (BRs) and 6-ketone upon the biological activity
of the alga Chlorella vulgaris (Chlorophyceae). The results of the study indicate significant differences in the growth and metabolism of C. vulgaris cells caused by the different chemical structures of the BRs used. The most significant differences in the stimulation of
the growth of the biomass and metabolites contained in it were caused by structural differences in the B ring of BRs. It was
found that in C. vulgaris 7-oxalactone type of BRs [brassinolide (BL) and its derivatives] are more active than 6-ketone type of BRs [castasterone
(CS) and its derivatives]. It was found that BRs used within the range of concentration of 10−12 to 10−8
m stimulate two- to threefold the growth and division of C. vulgaris cells. The most stimulating influence upon the number of the algal cells and the phosphorus, chlorophyll, and monosaccharides
contained in the alga, as well as the intensity of the photosynthesis, and sugar and glycolate excretion was demonstrated
by BL at a concentration 10−8
m in the 36th h of cultivation. HomoCS was characterized by the lowest biological activity. In turn, after the 48th h an inhibition
of the rate of growth and development of the alga takes place. In the range from 10−7 to 10−6
m the inhibition of growth and development of the alga was manifested by BRs. During the further toxic activity of BRs the
cells of C. vulgaris undergo complete degradation. In turn, in concentrations lower than 10−12
m, BRs do not exert any biologically significant influence upon C. vulgaris cells.
On the basis of the study, the biological activity of BRs was arranged in the following order: BL > 24-epiBL > homoBL > CS
> 24-epiCS > homoCS.
Received July 21, 1997; accepted April 7, 1998 相似文献
13.
R. L. Jarret 《Journal of Plant Growth Regulation》1997,16(4):227-231
Plant growth retardants were evaluated for their ability to reduce the growth rate of sweetpotato (Ipomoea batatas (L.) Lam.) in vitro. Nodal sections of cv. Jewel were cultured for 30 days on medium containing NDA, ancymidol, phosfon,
TIBA, difenzoquat, chlormequat, ACC, mepiquat chloride, or daminozide at 0, 10−4, 10−5, 10−6, 10−7, or 10−8
m. Difenzoquat, NDA, phosfon, and TIBA, at 10−4
m, were lethal to axillary bud explants. A low concentration (10−8
m) of chlorflurenol or NDA stimulated shoot elongation. The effective concentration range for most growth retardants was 10−5 to 10−6
m. Small (2- to 4-mm diameter) storage root-like swellings were observed on roots in cultures containing TIBA or ancymidol.
The growth-inhibiting effects of ancymidol and NDA were transitory and did not persist through a 180-day culture period. Shoots
cultured on medium containing 10−5
m phosfon, TIBA, or difenzoquat were significantly shorter than control plants after a 180-day culture period. Culture on medium
containing TIBA, NDA, ancymidol, or ACC resulted in abnormal leaf and stem development. Plants derived from nodal explants
cultured on medium containing either phosfon or chlormequat were near normal in appearance but with some plants exhibiting
interveinal chlorosis and reduced root system development.
Received May 9, 1997; accepted August 14, 1997 相似文献
14.
To study vacuolar chloride (Cl−) transport in the halophilic plant Mesembryanthemum crystallinum L., Cl− uptake into isolated tonoplast vesicles was measured using the Cl−-sensitive fluorescent dye lucigenin (N,N′-dimethyl-9,9′-bisacridinium dinitrate). Lucigenin was used at excitation and emission wavelengths of 433 nm and 506 nm,
respectively, and showed a high sensitivity towards Cl−, with a Stern-Volmer constant of 173 m
−1 in standard assay buffer. While lucigenin fluorescence was strongly quenched by all halides, it was only weakly quenched,
if at all, by other anions. However, the fluorescence intensity and Cl−-sensitivity of lucigenin was shown to be strongly affected by alkaline pH and was dependent on the conjugate base used as
the buffering ion. Chloride transport into tonoplast vesicles of M. crystallinum loaded with 10 mm lucigenin showed saturation-type kinetics with an apparent K
m
of 17.2 mm and a V
max
of 4.8 mm min−1. Vacuolar Cl− transport was not affected by sulfate, malate, or nitrate. In the presence of 250 μm
p-chloromercuribenzene sulfonate, a known anion-transport inhibitor, vacuolar Cl− transport was actually significantly increased by 24%. To determine absolute fluxes of Cl− using this method, the average surface to volume ratio of the tonoplast vesicles was measured by electron microscopy to be
1.13 × 107 m−1. After correcting for a 4.4-fold lower apparent Stern-Volmer constant for intravesicular lucigenin, a maximum rate of Cl− transport of 31 nmol m−2 sec−1 was calculated, in good agreement with values obtained for the plant vacuolar membrane using other techniques.
Received: 18 February 2000/Revised: 30 June 2000 相似文献
15.
To examine the involvement of Na+,K+,2Cl− cotransport in monovalent ion fluxes in vascular smooth muscle cells (VSMC), we compared the effect of bumetanide on 86Rb, 36Cl and 22Na uptake by quiescent cultures of VSMC from rat aorta. Under basal conditions, the values of bumetanide-sensitive (BS) inward
and outward 86Rb fluxes were not different. Bumetanide decreased basal 86Rb uptake by 70–75% with a K
i
of ∼0.2–0.3 μm. At concentrations ranging up to 1 μm, bumetanide did not affect 36Cl influx and reduced it by 20–30% in the range from 3 to 100 μm. In contrast to 86Rb and 36Cl influx, bumetanide did not inhibit 22Na uptake by VSMC. BS 86Rb uptake was completely abolished in Na+- or Cl−-free media. In contrast to 86Rb, basal BS 36Cl influx was not affected by Na+
o
and K+
o
. Hyperosmotic and isosmotic shrinkage of VSMC increased 86Rb and 36Cl influx to the same extent. Shrinkage-induced increments of 86Rb and 36Cl uptake were completely abolished by bumetanide with a K
i
or ∼0.3 μm. Shrinkage did not induce BS 86Rb and 36Cl influx in (Na+ or Cl−)- and (Na+ or K+)-depleted media, respectively. In the presence of an inhibitor of Na+/H+ exchange (EIPA), neither hyperosmotic nor isosmotic shrinkage activated 22Na influx. Bumetanide (1 μm) did not modify basal VSMC volume and intracellular content of sodium, potassium and chloride but abolished the regulatory
volume increase in isosmotically-shrunken VSMC. These data demonstrate the absence of the functional Na+,K+,2Cl− cotransporter in VSMC and suggest that in these cells basal and shrinkage-induced BS K+ influx is mediated by (Na+
o
+ Cl−
o
)-dependent K+/K+ exchange and Na+
o
-dependent K+,Cl− cotransport, respectively.
Received: 30 January 1996/Revised: 20 May 1996 相似文献
16.
The hyperpolarization of the electrical plasma membrane potential difference has been identified as an early response of
plant cells to various signals including fungal elicitors. The hyperpolarization-activated influx of Ca2+ into tomato cells was examined by the application of conventional patch clamp techniques. In both whole cell and single-channel
recordings, clamped membrane voltages more negative than −120 mV resulted in time- and voltage-dependent current activation.
Single-channel currents saturated with increasing activities of Ca2+ and Ba2+ from 3 to 26 mm and the single channel conductance increased from 4 pS to 11 pS in the presence of 20 mm Ca2+ or Ba2+, respectively. These channels were 20–25 and 10–13 times more permeable to Ca2+ than to K+ and to Cl−, respectively. Channel currents were strongly inhibited by 10 μm lanthanum and 50% inhibited by 100 μm nifedipine. This evidence suggests that hyperpolarization-activated Ca2+-permeable channels provide a mechanism for the influx of Ca2+ into tomato cells.
Received: 13 February 1996/Revised: 12 August 1996 相似文献
17.
Jafar Seyfabadi Zohreh Ramezanpour Zahra Amini Khoeyi 《Journal of applied phycology》2011,23(4):721-726
The effects of irradiance and photoperiod on growth rates, chlorophyll a, β-carotene, total protein, and fatty acid content of Chlorella vulgaris were determined. The maximum growth rate (1.13 day−1) was at 100 μmol photons m−2 s−1 and 16:8-h light/dark photoperiod. Chlorophyll a and β-carotene contents significantly differed under different light regimes with chlorophyll a content lower at high irradiance and longer light duration, while β-carotene showed the inverse trend. The total protein
and fatty acid content also significantly differed in different light regimes; the maximum percentage of protein (46%) was
at 100 μmol photons m−2 s−1 and 16:8 h photoperiod, and minimum (33%) was at 37.5 μmol photons m−2 s−1 and 8:16 h photoperiod; the total saturated fatty acids increased, while monounsaturated and polyunsaturated fatty acids
decreased with increasing irradiance and light duration. 相似文献
18.
Significance of betaines in the increased chlorophyll content of plants treated with seaweed extract 总被引:2,自引:0,他引:2
Seaweed extract, prepared by alkaline extraction of Ascophyllum nodosum (L.) Le Jol., applied either to the soil or to the foliage of tomato plants, produced leaves with higher chlorophyll levels
than those of control plants. The effects on leaf chlorophyll content were investigated using a cucumber bioassay procedure
devised for cytokinins. The seaweed extract was shown to increase the chlorophyll levels of the cucumber cotyledons, but ‘peaks’
of activity were obtained when widely different concentrations were used. The possibility that these effects were the result
of betaines present in the extract was considered. Glycinebetaine, γ-aminobutyric acid betaine and δ-aminovaleric acid betaine
all produced significantly enhanced chlorophyll concentrations in the cotyledons. ‘Peaks’ of activity were observed for each
betaine: for glycinebetaine at 10−6 and between 10−4 and 101 mg 1−1, for γ-aminobutyric acid betaine at 10−6, between 10−4 and 10−1, and 101 mg 1−1, and for δ-aminovaleric acid betaine between 10−5 and 101 mg 1−1. It was concluded that the effects of enhancing chlorophyll levels produced by the seaweed extract were due, at least in
part, to betaines. 相似文献
19.
It has previously been shown that osmotic cell shrinkage activates a nonselective cation (NSC) channel in M-1 mouse cortical
collecting duct cells [54] and in a variety of other cell types [20]. In the present study we further characterized the shrinkage-activated
NSC channel in M-1 cells and its mechanism of activation using whole-cell current recordings. Osmotic cell shrinkage induced
by addition of 100 mm sucrose to the bath solution caused a 20-fold increase in whole-cell inward currents from −10.8 ± 1.5 pA to −211 ± 10.2 pA
(n= 103). A similar response was observed when cell shrinkage was elicited using a hypo-osmotic pipette solution. This indicates
that cell shrinkage and not extracellular osmolarity per se is the signal for current activation. Cation substitution experiments revealed that the activated channels discriminate poorly
between monovalent cations with a selectivity sequence NH4 (1.2) ≥ Na+ (1) ≈ K+ (0.9) ≈ Li+ (0.9). In contrast there was no measurable permeability for Ca2+ or Ba2+ and the cation-to-anion permeability ratio was about 14. The DPC-derivatives flufenamic acid, 4-methyl-DPC and DCDPC were
the most effective blockers followed by LOE 908, while amiloride and bumetanide were ineffective. The putative channel activator
maitotoxin had no effect. Current activation was dependent upon the presence of intracellular ATP and Mg2+ and was inhibited by staurosporine (1 μm) and calphostin C (1 μm). Moreover, cytochalasin D (10 μm) and taxol (2 μm) reduced the current response to cell shrinkage. These findings suggest that the activation mechanism of the shrinkage-activated
NSC channel involves protein kinase mediated phosphorylation steps and cytoskeletal elements.
Received: 3 May 2000/Revised: 6 July 2000 相似文献
20.
The diffusion coefficients of four solutes ranging in molecular weight from 238 to 10,000 in the lateral intercellular spaces
(LIS) of cultured kidney cells (MDCK) grown on permeable supports were determined from the spread of fluorescence produced
after the release of caged compounds by a pulse from a UV laser. Two types of experiments were performed: measurement of the
rate of change of fluorescence after releasing a caged fluorophore, and measurement of the change in fluorescence of a relatively
static fluorescent dye produced by the diffusion of an uncaged ligand for the dye. Fluorescence intensity was determined by
photon-counting the outputs of a multichannel photomultiplier tube. Diffusion coefficients were determined in free solution
as well as in the LIS of MDCK cells grown on permeable supports and the hindrance factor, θ, determined from the ratio of
the free solution diffusivity to that in the LIS. The hindrance factors for 3000-MW dextran, 8-hydroxypyrene-1,3,6-trisulfonic
acid (HPTS, MW 524) and N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid (HEPES, MW 238) were not significantly different
from 1. The diffusion of 10,000-MW dextran was substantially reduced in the LIS with a θ of 5.6 ± 0.3. Enzymatic digestion
by neuraminidase of the sialic acid residues of the glycosylation groups in the LIS increased the diffusivity of the 10,000-MW
dextran 1.8-fold indicating hindrance by the glycocalyx. We conclude that small solutes, such as Na+ and Cl−, would not be significantly restricted in their diffusion in the LIS and that solute concentration gradients could not develop
along the LIS under physiologic conditions.
Received: 7 October 1999 相似文献