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1.
The effect of application of GA3 on hypocotyl growth, the endogenous GAs, and the metabolism of applied 3H-GA1 were investigated in relation to dwarfism and light-mediated growth inhibition in the normal (tall) strain Violet and the dwarf strain Kidachi of Japanese morning glory (Pharbitis nil). GA3 applied in a wide concentration range (10−9 to 10−3m) to 4-day-old seedlings caused great extension of the hypocotyls in light-grown plants of both the normal and the dwarf strain. However, the dwarf strain did not attain the same length as the normal one at any given GA3 concentration, even when saturation was reached. Dark-grown plants of the dwarf strain responded to GA3, although relatively much less than light-grown ones; dark-grown plants of the normal strain showed no GA3 response at all.  相似文献   

2.
Hiatt AJ 《Plant physiology》1967,42(2):294-298
Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K2SO4, CaCl2, and NaCl solutions at concentrations of 10−5 to 10−2 n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10−5 n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10−3 n K2SO4. Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake.  相似文献   

3.
The influence of NO3 uptake and reduction on ionic balance in barley seedlings (Hordeum vulgare, cv. Compana) was studied. KNO3 and KCl treatment solutions were used for comparison of cation and anion uptake. The rate of Cl uptake was more rapid than the rate of NO3 uptake during the first 2 to 4 hours of treatment. There was an acceleration in rate of NO3 uptake after 4 hours resulting in a sustained rate of NO3 uptake which exceeded the rate of Cl uptake. The initial (2 to 4 hours) rate of K+ uptake appeared to be independent of the rate of anion uptake. After 4 hours the rate of K+ uptake was greater with the KNO3 treatment than with the KCl treatment, and the solution pH, cell sap pH, and organic acid levels with KNO3 increased, relative to those with the KCl treatment. When absorption experiments were conducted in darkness, K+ uptake from KNO3 did not exceed K+ uptake from KCl. We suggest that the greater uptake and accumulation of K+ in NO3-treated plants resulted from (a) a more rapid, sustained uptake and transport of NO3 providing a mobile counteranion for K+ transport, and (b) the synthesis of organic acids in response to NO3 reduction increasing the capacity for K+ accumulation by providing a source of nondiffusible organic anions.  相似文献   

4.
Moore TC 《Plant physiology》1967,42(5):677-684
The capacities of indole-3-acetic acid (IAA) and gibberellin A3 (GA3) to counteract the inhibitory effects of (2-chloroethyl) trimethylammonium chloride (CCC), 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride (Amo-1618), and N,N-dimethylaminosuccinamic acid (B-995) on hypocotyl elongation in light-grown cucumber (Cucumis sativus L.) seedlings were investigated. One μg of GA3 applied to the shoot tip was sufficient to completely nullify the effect of 10 μg of Amo-1618 or 25 μg of B-995 applied simultaneously to the shoot tip, and 10 μg of GA3 completely counteracted the effect of 10−3 m CCC added to the root medium. One μg of IAA counteracted the effect of 10−3 m CCC in the root medium, but IAA did not nullify the action of either Amo-1618 or B-995. Experiments were conducted using 2 growth retardants simultaneously, which indicated that Amo-1618 and CCC inhibit a common process, namely GA biosynthesis, essential to hypocotyl elongation. However, since the effect of CCC was overcome by applications of both GA and IAA, growth retardation resulting from treatment with CCC apparently is not due solely to inhibition of GA biosynthesis. B-995 did not interact additively with either Amo-1618 or CCC, which suggests that B-995 affects a process different from those affected by the other 2 retardants. Thus, while inhibition evoked by B-995 is reversible by applied GA, the action of B-995 does not appear to be inhibition of GA biosynthesis.  相似文献   

5.
Gibberellic acid (GA3) induces invertase activity within 6 hours in Avena stem segments that are incubated in the dark at 23°. The maximum amount of promotion is about 5 times that of invertase activity in untreated segments. GA3 causes significant promotion of invertase activity at concentrations as low as 3 × 10−5 μm GA3. The increase in invertase activity elicited by GA3 between 3 × 10−5 μm and 300 μm closely parallels the growth promotion that is caused by GA3 over this concentration range. In control segments, invertase activity rises steeply during the first 6 hours of incubation, then decays slowly between 12 and 48 hours. In GA3-treated segments, the invertase activity also rises during the first 6 hours, parallel to that in control segments and continues to rise during the next 42 hours. These changes in invertase activity during 48-hour incubation periods do not parallel the changes in growth that occur in control and GA3-treated segments. Cycloheximide at 10 μg/ml abolishes all GA3-promoted growth and invertase activity in these segments. Actinomycin D at 40 and 80 μg/ml decreases GA3-promoted growth by 20% and invertase activity by 38 and 44%, respectively. The data clearly support the idea that protein synthesis is necessary for GA3-promoted growth and invertase activity in Avena stem segments.  相似文献   

6.
Cell elongation and cell division in elongating lettuce hypocotyl sections   总被引:1,自引:1,他引:0  
The roles of cell division and cell elongation in the growth of sections excised from hypocotyls of lettuce (Lactuca sativa L. cv. Arctic) were investigated. Elongation of sections incubated in the light is inhibited compared to dark-grown sections and this inhibition is reversed by gibberellic acid (GA3). The elongation of both dark-grown and GA3-treated, light-grown sections can be enhanced by 10mM KCl. Under all conditions of incubation, elongation growth is greatest in the uppermost quarter of the hypocotyl section while the basal quarter does not elongate. In darkness the two apical segments of sections marked into four equal parts grow at the same rate, while in light, growth of the apical segment exceeds that of the second segment. Cell division in cortical or epidermal cells, as measured by mitotic index or cell number, is not affected by illumination conditions nor by GA3 or KCl treatments. Although -irradiation and FUDR pretreatment eliminate or cause a marked reduction in cell division in the excised hypocotyl, sections from seeds irradiated with -rays or incubated in 5-fluorodeoxyuridine elongate in response to GA3 and KCl treatment as do sections from non-pretreated controls. Therefore, since neither GA3 nor darkness affect celldivision activity and since treatments which eliminate or significantly reduce cell division do not affect growth, we conclude that the effect of GA3 and darkness in this material is to increase cell elongation.Abbreviations FUDR 5-fluorodeoxyuridine - GA(s) gibberellin(s) - GA3 gibberellic acid  相似文献   

7.

Background and Aims

The mechanism of auxin action on ion transport in growing cells has not been determined in detail. In particular, little is known about the role of chloride in the auxin-induced growth of coleoptile cells. Moreover, the data that do exist in the literature are controversial. This study describes experiments that were carried out with maize (Zea mays) coleoptile segments, this being a classical model system for studies of plant cell elongation growth.

Methods

Growth kinetics or growth and pH changes were recorded in maize coleoptiles using two independent measuring systems. The growth rate of the segments was measured simultaneously with medium pH changes. Membrane potential changes in parenchymal cells of the segments were also determined for chosen variants. The question of whether anion transport is involved in auxin-induced growth of maize coleoptile segments was primarily studied using anion channel blockers [anthracene-9-carboxylic acid (A-9-C) and 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS)]. In addition, experiments in which KCl was replaced by KNO3 were also performed.

Key Results

Both anion channel blockers, added at 0·1 mm, diminished indole-3-acetic acid (IAA)-induced elongation growth by ∼30 %. Medium pH changes measured simultaneously with growth indicated that while DIDS stopped IAA-induced proton extrusion, A-9-C diminished it by only 50 %. Addition of A-9-C to medium containing 1 mm KCl did not affect the characteristic kinetics of IAA-induced membrane potential changes, while in the presence of 10 mm KCl the channel blocker stopped IAA-induced membrane hyperpolarization. Replacement of KCl with KNO3 significantly decreased IAA-induced growth and inhibited proton extrusion. In contrast to the KCl concentration, the concentration of KNO3 did not affect the growth-stimulatory effect of IAA. For comparison, the effects of the cation channel blocker tetraethylammonium chloride (TEA-Cl) on IAA-induced growth and proton extrusion were also determined. TEA-Cl, added 1 h before IAA, caused reduction of growth by 49·9 % and inhibition of proton extrusion.

Conclusions

These results suggest that Cl plays a role in the IAA-induced growth of maize coleoptile segments. A possible mechanism for Cl uptake during IAA-induced growth is proposed in which uptake of K+ and Cl ions in concert with IAA-induced plasma membrane H+-ATPase activity changes the membrane potential to a value needed for turgor adjustment during the growth of maize coleoptile cells.  相似文献   

8.
The roles of gibberellic acid (GA3) and fusicoccin (FC) in the elongation growth and acidification of the medium by excised hypocotyl sections of lettuce (Lactuca sativa L.) were investigated. Hypocotyl sections incubated in buffer without GA3 elongate optimally at pH 4.0–4.25 while sections incubated with GA3 show the same growth between pH 4.25 and 6.0. Preincubation of sections at pH 6.0 for 6 h does not affect the subsequent elongation response to acidic medium (pH 4.25); however, the sections become refractory to further acid treatment after their initial burst of growth in response to pH 4.25. Sections made refractory to acid are responsive to GA3 application, however, and the rate of growth in response to GA3 of sections pretreated for 6 h at pH 4.25 is 85% of that of sections pretreated at pH 6.0. Although preincubation of sections for 48 h in medium at pH 6.0 abolishes the GA3 response, it does not affect the response to buffer at pH 4.25. FC stimulates elongation growth in letuce hypocotyls at an optimal concentration of 1 M, and pretreatment of sections at pH 4.25 does not affect this elongation response. Although both GA3 and FC increase elongation of the section, neither causes appreciable acidification of the medium. Addition of KCl or NaCl to FC-treated sections causes rapid medium acidification but addition of salts to GA3-treated tissue does not cause acidification. Abrasion of the hypocotyl to remove the cuticle does not enhance acidification of the medium by the sections nor deos it affect elongation of the sections in response to GA3 or FC. Medium acidification by the sections is not a passive process since it is abolished both by low temperature (2° C) and metabolic inhibitors (carbonyl cyanide-m-chlorophenyl-hydrazone, azide). The acidification of the medium by barley (Hordeum vulgare L.) roots in response to FC is also dependent on the presence of KCl. We conclude that the acid-growth hypothesis does not explain GA3- or FC-induced elongation in lettuce hypocotyls.Abbreviations FC tusicoccin - GA3 gibberellic acid - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - CCCP carbonyl cyanide-m-chlorophenyl-hydrazone - MES 2-(N-morpholino)ethanesulphonic acid - Tris tris-(hydroxymethyl)aminomethane  相似文献   

9.
The rest period of the potato tuber was studied in relation to certain biochemical changes that are induced by gibberellic acid (GA3). The concentration of reducing sugars in excised plugs with buds treated with 10−4m GA3 decreased in the first 4 hours after treatment and then rapidly increased up to 70 hours. The pattern in control buds was similar, but the changes occurred more slowly. The response to GA3 is temperature-dependent and is not limited to any particular tissue of the tuber. The concentration of reducing sugars in excised buds increased proportionally to the log of the concentration of GA3 in a range from 10−8 to 10−4m. At 10−3m, GA3 slightly inhibited production of reducing sugars. Malonate inhibits the initial decrease and the subsequent increase in reducing sugars in control buds, but not the increase induced by GA3.  相似文献   

10.
Jones KC 《Plant physiology》1969,44(12):1695-1700
Barley endosperm halves release acid phosphatase in response to several gibberellins and gibberellin precursors. Seed halves incubated with 10−7m GA3 at 29° begin to release phosphatase after 11 hr and release it for another 26 hr in response to GA3. After 37 hr, the rate of release slows to that of seed halves incubated without GA3. GA3 is active at 10−10m and maximally active at 10−7m. Comparative activity of 12 gibberellins and gibberellin precursors is GA1 = GA3 > GA2 > GA4 = GA7 > GA5 = GA13 > GA14 > GA8 = GA9 > (−)kaurenoic acid > (−)-kaurene. These compounds show the same order of activity and approximately the same relative activity in inducing reducing sugar release as in inducing phosphatase activity. The activity of each compound increases with its presumed position in a biosynthetic pathway leading from kaurene to GA3. This correlation suggests that activity may be a reflection of the efficiency of conversion to an active form within the seed half.  相似文献   

11.
pICln has been proposed to be the swelling-activated anion channel responsible for ICl, swell, or a channel regulator. We tested the anion channel hypothesis by reconstituting recombinant pICln into artificial and biological membranes. Single channels were observed when pICln was reconstituted into planar lipid bilayers. In the presence of symmetrical 300 mM KCl, the channels had a high open probability and a slope conductance of 48 pS, and were outwardly rectifying. Reduction of trans KCl to 50 mM shifted the reversal potential by −31.2 ± 0.06 mV, demonstrating that the channel is at least seven times more selective for cations than for anions. Consistent with this finding, channel conductance was unaffected by substitution of Cl with glutamate, but was undetectable when K+ was replaced by N-methyl-d-glucamine. Reconstitution of pICln into liposomes increased 86Rb+ uptake by three- to fourfold, but had no effect on 36Cl uptake. Phosphorylation of pICln with casein kinase II or mutation of G54, G56, and G58 to alanine decreased channel open probability and 86Rb+ uptake. When added to the external medium bathing Sf9 cells, pICln inserted into the plasma membrane and increased cell cation permeability. Taken together, these observations demonstrate that channel activity is due to pICln and not minor contaminant proteins. However, these findings do not support the hypothesis that pICln is the anion-selective ICl, swell channel. The observed cation channel activity may reflect an as yet to be defined physiological function of pICln, or may be a consequence of in vitro reconstitution of purified, recombinant protein.  相似文献   

12.
Wheat seedlings (Triticum vulgare) treated with 1 mm KNO3 or NaNO3, in the presence of 0.2 mm CaSO4, were compared during a 48-hour period with respect to nitrate uptake, translocation, accumulation and reduction; cation uptake and accumulation; and malate accumulation. Seedlings treated with KNO3 absorbed and accumulated more nitrate, had higher nitrate reductase levels in leaves but less in roots, accumulated 17 times more malate in leaves, and accumulated more of the accompanying cation than seedlings treated with NaNO3. Within seedlings of each treatment, changes in nitrate reductase activity and malate accumulation were parallel in leaves and in roots. Despite the great difference in malate accumulation, leaves of the KNO3-treated seedlings had only slightly greater levels of phosphoenolpyruvate carboxylase than leaves of NaNO3-treated seedlings. NADP-malic enzyme levels increased only slightly in leaves and roots of both KNO3- and NaNO3-treated seedlings. The effects of K+ and Na+ on all of these parameters can best be explained by their effects on nitrate translocation, which in turn affects the other parameters. In a separate experiment, we confirmed that phosphoenolpyruvate carboxylase activity increased about 2-fold during 36 hours of KNO3 treatment, and increased only slightly in the KCl control.  相似文献   

13.
The growth and IAA-oxidase activity of light-grown cucumber seedlings (cv. Aonagajibae) were investigated in response to GA3 and IAA. Both GA3 and IAA induced significant elongation of the hypocotyl. The fresh and dry weights of the hypocotyl increased due to GA3 or IAA treatment, whereas no significant change was observed in the cotyledons of GA3-treated seedlings as compared with the controls. The fresh and dry weights of IAA-treated cotyledons were both lower than those of controls. Treatment with GA3 or IAA resulted in retardation of IAA-oxidase activity in the hypocotyl and cotyledons. The degree of retardation was less in the cotyledons than in the hypocotyl. An inverse relationship was recognized between GA3- or IAA-induced elongation and IAA-oxidase activity in the hypocotyl. The auxin-mediated mechanism for gibberellin action was discussed.  相似文献   

14.
Ricinus communis L. plants were grown in nutrient solutions in which N was supplied as NO3 or NH4+, the solutions being maintained at pH 5.5. In NO3-fed plants excess nutrient anion over cation uptake was equivalent to net OH efflux, and the total charge from NO3 and SO42− reduction equated to the sum of organic anion accumulation plus net OH efflux. In NH4+-fed plants a large H+ efflux was recorded in close agreement with excess cation over anion uptake. This H+ efflux equated to the sum of net cation (NH4+ minus SO42−) assimilation plus organic anion accumulation. In vivo nitrate reductase assays revealed that the roots may have the capacity to reduce just under half of the total NO3 that is taken up and reduced in NO3-fed plants. Organic anion concentration in these plants was much higher in the shoots than in the roots. In NH4+-fed plants absorbed NH4+ was almost exclusively assimilated in the roots. These plants were considerably lower in organic anions than NO3-fed plants, but had equal concentrations in shoots and roots. Xylem and phloem saps were collected from plants exposed to both N sources and analyzed for all major contributing ionic and nitrogenous compounds. The results obtained were used to assist in interpreting the ion uptake, assimilation, and accumulation data in terms of shoot/root pH regulation and cycling of nutrients.  相似文献   

15.
Gibberellin response in lettuce hypocotyl sections   总被引:9,自引:7,他引:2       下载免费PDF全文
Silk WK  Jones RL 《Plant physiology》1975,56(2):267-272
Excised lettuce (Lactuca sativa L.) hypocotyl sections retain the ability to elongate in response to gibberellic acid (GA3) addition. In 48 hr at 30 C a GA3-treated segment more than doubles while a control segment elongates less than 50%. Auxin has no detectable effect on this system. Sensitivity to GA3 is not decreased by apex or root removal. Of the experimental variables tested, temperature, sucrose, and preincubation in water affect growth both with and without GA3. Blue and far red light inhibit growth without GA3; this inhibition is reversed by GA3. Potassium chloride stimulates growth of illuminated sections treated with GA3 but has no effect on control growth. When sections are incubated in the dark, KCl has a promotive effect on elongation.  相似文献   

16.
Analysis of NaCl toxicity in Chlorella sorokiniana showed decreased growth rates, increased dry weight per cell, increased intracellular Na+ and Cl, more total chlorophyll per cell, a decreased chlorophyll a to chlorophyll b ratio, increased rates of O2 evolution, and decreased rates of CO2 fixation when the extracellular concentration of NaCl was increased from zero to 0.3 m. Cultures did not grow at concentrations greater than 0.3 m NaCl unless 10 mm calcium salts were present. Inclusion of that concentration of Ca2+ extended the tolerance to 0.5 m NaCl before growth stopped. Increasing the light intensity from 1.2 to 9.4 mw/cm2 increased growth rates for cultures in 0.10 to 0.45 m NaCl. At 14 mw/cm2 added Ca2+ reduced growth rates of cultures in 0.3 m NaCl compared to controls without added Ca2+. Maximal growth rates for cultures in NaCl media were achieved by addition of 10 mm CaSO4 and maintenance of the light intensity at 9.4 mw/cm2. The maximal growth rate of the organism was 9.6 doublings/day achieved at 2.7 mw/cm2 for control cultures. In 0.3 m NaCl the growth rate was 4.3 doublings/day at 2.7 mw/cm2 and 8.2 doublings/day at 9.4 mw/cm2 with 10 mm CaSO4 added.  相似文献   

17.
Pesci P 《Plant physiology》1988,86(3):927-930
The increase in proline induced by ABA, a process stimulated by NaCl or KCl in barley leaves, did not occur when Na+ (or K+) was present in the external medium as the gluconate salt, namely with an anion unable to permeate the plasma membrane. However, proline increase was restored, to different extents, by the addition of various chloride salts but not by ammonium chloride. Moreover, it was shown that the stimulation of the process by NaCl (or KCl) was variously affected by the presence of different salts; all the ammonium salts (10 millimolar NH4+ concentration) inhibited this stimulation almost completely. Inhibition by NH4+ was accompanied by a decreased Na+ influx (−40%). Also, in the case of Na-gluconate, Na+ uptake was reduced and the addition of Cl as the calcium or magnesium salt (but not as ammonium salt) restored both the ion influxes and the increase in proline typical of NaCl treatments. Both 4,4′-diisothiocyano-2,2′-disulfonic acid stilbene (DIDS), an anion transport inhibitor, and tetraethylammonium chloride (TEA), a K+ channels-blocking agent, caused, as well as with a reduction of ion influxes, an inhibition of the proline accumulation. The inhibition was practically total with 1 millimolar DIDS and about 80% with 20 millimolar TEA. A possible role of ion influxes in the process leading to the increase in proline induced by ABA is proposed.  相似文献   

18.
Week-old wheat seedlings absorbed at least 40% NO3 from NaNO3 when preloaded with K+ than when preloaded with Na+ or Ca2+. Cultures of Triticum vulgare L. cv. Arthur were grown for 5 days on 0.2 mm CaSO4, pretreated for 48 hours with either 1 mm CaSO4, K2SO4, or Na2SO4, and then transferred to 1 mm NaNO3. All solutions contained 0.2 mm CaSO4. Shoots of K+-preloaded plants accumulated three times more NO3 than shoots of the other two treatments. Initially, the K+-preloaded plants contained 10-fold more malate than either Na+- or Ca2+-preloaded seedlings. During the 48-hour treatment with NaNO3, malate in both roots and shoots of the K+-preloaded seedlings decreased. Seedlings preloaded with K+ reduced 25% more NO3 than those preloaded with either Na+ or Ca2+. These experiments indicate that K+ enhanced NO3 uptake and reduction even though the absorption of K+ and NO3 were separated in time. Xylem exudate of K+-pretreated plants contained roughly equivalent concentrations of K+ and NO3, but exudate from Na+ and Ca2+-pretreated plants contained two to four times more NO3 than K+. Therefore K+ is not an obligatory counterion for NO3 transport in xylem.  相似文献   

19.
Sodium uptake by rainbow trout gills has been investigated with a small-volume system enabling rapid, successive flux measurements in different solutions. Sodium influx obeys a Michaelis-Menten type relation, with a Km of 0.46 mM, and uptake proceeds unimpaired in the absence of penetrating counter-ions. This suggests a coupled cation exchange. Ammonia output is about the same as the Na+ influx when external [Na+] is 1 mM, but at higher or lower Na+ influxes, the correlation does not hold. A progressive downward shift in the pH of the irrigating medium as Na+ influx increases indicates that the exchanging cation is hydrogen. In support of this, acetazolamide, which inhibits Na+ uptake, also prevents the downward pH shift. The potential across the gill is about 10 mv, body fluids positive, in NaCl solutions up to 10 mM, and is little affected by changes in Na+ concentration below that. Finally, evidence for locating the rate-limiting step at the outer membrane of the epithelium is presented.  相似文献   

20.
Hiatt AJ 《Plant physiology》1970,45(4):411-414
Excised barley roots accumulated 40 to 50% more K+ from 0.04 mm than from 0.06 mm KCl when incubated for 24 hours in KCl solutions containing 0.2 mm CaSO4. This phenomenon was not markedly influenced by the rate of absorption of the counteranion. The presence of Na+ in the treatment solutions decreased total K accumulation but did not alter the K+ concentration at which the accumulation peak occurred. Short interval studies indicated that this phenomenon is easily observable after 4 hours and begins to become apparent within 2 hours. In comparison with barley, accumulation of K+ by excised wheat roots decreased as KCl concentration was increased from 0.02 to 0.06 mm; but K+ accumulation curve for corn roots showed no peaks or depressions in the concentration range of 0.01 to 0.1 mm. A normal hyperbolic curve was noted for the accumulation of Na+ from 0.01 to 1 mm NaCl by barley roots.  相似文献   

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