共查询到20条相似文献,搜索用时 13 毫秒
1.
We have characterized the transport of [3H]indoleacetic acid (IAA) in intact corn (Zea mays L.) coleoptiles. We have used a wide range of concentrations of added IAA (28 femtomoles to 100 picomoles taken up over 60 minutes). The shape of the transport curve varies with the concentration of added IAA, although the rate of movement of the observed front of tracer is invariant with concentration. At the lowest concentration of tracer used, the labeled IAA in the transport stream is not detectably metabolized or immobilized, curvature does not develop as a result of tracer application, and normal phototropic and gravitropic responsiveness are not affected. Therefore we believe we are observing the transport of true tracer quantities of labeled auxin at this lowest concentration. 相似文献
2.
Summary Indoleacetic acid (IAA)-5-3H (2×10-9) was applied to intact roots of Phaseolus coccineus seedlings at the apex or 2 cm above the apex, and the movement of IAA-3H and its metabolites traced by sectioning and chromatography. Basipetal movement of label occurred for 2 cm or less, declining exponentially, and the amount increased with time. Acropetal transport from above the apex showed quantitatively less movement of radioactivity. After a 6h treatment period a decline of label occurred in the first 0.5cm, below which there was a long distance movement of small amounts of label, mainly in IAA, towards the apex where the label concentrated by a factor of approximately 2. Short-distance basipetal movement consisted of about equal amounts of IAA and metabolites, and only metabolites were found in areas more basipetal than 2cm. Label from solutions of sucrose-14C and 3H2O followed the same general pattern of movement as label from IAA-3H, except that acropetal movement of water showed a steady decrease in the amount of label as the distance from the area of application increased. The short distance basipetal transport of label with the breakdown of IAA-3H indicates that the extent of basipetal movement was limited by catabolic processes. The acropetal pattern of IAA-3H movement with the concentration of the transported material close to the apex, is possibly the result of transport in the phloem. 相似文献
3.
Summary Part of the IAA-I- or IAA-2-14C applied at low concentrations to the apices of intact, light-grown dwarf pea seedling was transported unchanged to the root system The calculated velocity of transport in the stem was 11 mm per hour. In the root the label accumulated in the developing lateral root primordia.A large proportion of the applied IAA was converted by tissues of the apical bud, stem and root to indole-3-acetyl-aspartic acid (IAAsp). This compound was not transported. In addition evidence was obtained for the formation of IAA-protein complexes in the apex and roots, but not in the fully-expanded internodes.Large quantities of a decarboxylation product of IAA, tentatively indentified as indole-3-aldehyde (IAld), and several minor metabolites of IAA, were detected in extracts of the roots and first internodes, but not in the above-ground organs exposed to light. These compounds were readily transported through stem and root tissues. Together, the decarboxylation of IAA and the formation of IAAsp operated to maintain a relatively constant level of free IAA-14C in the root system. 相似文献
4.
Darbyshire B 《Plant physiology》1971,47(1):65-67
Activity of indoleacetic acid oxidase was shown to increase following a period of water stress. Two fractions of indoleacetic acid oxidase were extracted from plant extracts. Similarly, two protein peaks (determined by ultraviolet absorption) were isolated. One peak, associated with an indoleacetic acid oxidase peak, increased following water stress. The second peak, not associated with extractable indoleacetic acid oxidase, decreased after water stress. The results are discussed in terms of general growth effects. 相似文献
5.
Partial purification and kinetics of indoleacetic Acid oxidase from tobacco roots 总被引:3,自引:9,他引:3 下载免费PDF全文
Extracts from roots of Nicotiana tabacum L var. Bottom Special contain oxidative enzymes capable of rapid degradation of indoleacetic acid (IAA) in the presence of Mn2+ and 2, 4-dichlorophenol. Purification of IAA oxidase was attempted by means of ammonium sulfate fractionation and elution through a column of SE-Sephadex. Two distinct fractions, both causing rapid oxidation of IAA in the absence of H2O2, were obtained. One fraction exhibited high peroxidase activity when guaiacol was used as the electron donor; the other did not oxidase guaiacol. Both enzyme fractions caused similar changes in the UV spectrum of IAA; absorption at 280 mμ was reduced, while major absorption peaks appeared at 254 and 247 mμ. The kinetics of IAA oxidation by both fractions were followed by measuring the increase in absorption at 247 mμ. The peroxidase-containing fraction showed no lag or a slight lag which could be eliminated by addition of H2O2 (3 μmoles/ml). The peroxidase-free fraction showed a longer lag, but addition of similar amounts of H2O2 inhibited the rate of IAA oxidation and did not remove the lag. With purified preparations, IAA oxidation was stimulated only at low concentrations of H2O2 (0.03 μmole/ml). A comparison of Km values for IAA oxidation by the peroxidase-containing and peroxidase-free fractions suggests that tobacco roots contain an IAA oxidase which may have higher affinity for IAA and may be more specific than the general peroxidase system previously described from other plant sources. A similar oxidase is present in commercial preparations of horseradish peroxidase. It is suggested that oxidation of IAA by horseradish peroxidase may be due to a more specific component. 相似文献
6.
Cell wall and protoplast isoperoxidases in relation to injury, indoleacetic Acid, and ethylene effects 总被引:10,自引:7,他引:3 下载免费PDF全文
A number of plants have been surveyed with respect to isolation by mild grinding in large quantities of leaf cells. The extent of recovery of mesophyll cells per unit leaf area was found to vary with plant species and the method of grinding. Greater than 70% recovery was obtained from the leaves of Canna indica L., Crotalaria Laburnifolia L., and Thunbergia grandiflora Roxb. 相似文献
7.
Rapid modulation of nitrate reductase in pea roots 总被引:10,自引:0,他引:10
The regulatory properties of nitrate reductase (NR; EC 1.6.6.1) in root extracts from hydroponically grown pea (Pisum sativum L. cv. Kleine Rheinländerin) plants were examined and compared with known properties of NR from spinach and pea leaves. Nitrate-reductase activity (NRA) extracted from pea roots decreased slowly when plants were kept in the dark, or when illuminated plants were detopped, with a half-time of about 4 h (= slow modulation in vivo). In contrast, the half-time for the dark-inactivation of NR from pea leaves was only 10 min. However, when root tip segments were transferred from aerobic to anaerobic conditions or vice versa, changes in NRA were as rapid as in leaves (= rapid modulation in vivo). Nitrate-reductase activity was low when extracted from roots kept in solutions flushed with air or pure oxygen, and high in nitrogen. Okadaic acid, a specific inhibitor of type-1 and type-2A protein phosphatases, totally prevented the in vivo activation by anaerobiosis of NR, indicating that rapid activation of root NR involved protein dephosphorylation. Under aerobic conditions, the low NRA in roots was also rapidly increased by incubating the roots with either uncouplers or mannose. Under these conditions, and also under anaerobiosis, ATP levels in roots were much lower than in aerated control roots. Thus, whenever ATP levels in roots were artificially decreased, NRA increased rapidly. The highly active NR extracted from anaerobic roots could be partially inactivated in vitro by preincubation of desalted root extracts with MgATP (2 mM), with a half-time of about 20 min. It was reactivated by subsequently incubating the extracts with excess AMP (2 mM). Thus, pea root NR shares many of the previously described properties of NR from spinach leaves, suggesting that the root enzyme, like the leaf enzyme, can be rapidly modulated, probably by reversible protein phosphorylation/ dephosphorylation. 相似文献
8.
9.
7-Chloroindoleacetic acid and dichloroindoleacetic acids with a Cl in the 7 position showed anti-auxinic activity and promoted root growth in wheat ( Triticum aestivum L. cv. Diamant II). In contrast, 4-, 5- and 6-chloroindoleatetic acids acted as strong auxins inhibiting the growth of wheat roots. Flax ( Linum usitatissimum L. cv. Concurrent) and cucumber ( Cucumis sativus L. cv. Favör) roots showed similar, but less clear-cut responses. 7-Chloroindoleacetic acid and 4,7-dichloroindoleacetic acid alleviated root growth inhibition in wheat caused by IAA, monochloroindoleacetic acids and benzyladenine. 2,4-D, 4- and 6-chloroindoleacetic acids strongly induced ethylene formation in cucumber seedlings; 4,7- and 6,7-dichloroindoleacetic acids did not, except at high concentrations. The more lipid-soluble dichloroindoleacetic acids were stronger inhibitors of ATP formation in cucumber mitochondria than monochloroindoleacetic acids, while IAA itself had only a very slight effect. 相似文献
10.
Growth of the primary root of 12 genotypes of peas ( Pisum sativum ) differing in their stem height was recorded for 14 days. The growth rate of roots of wild-type tall, gibberellin (GA)-deficient le dwarf or slender mutants (with la crys ) was similar (3 cm day−1 ); that of severely GA-deficient nana ( na-1 ) plants was 50% of wild-type but elongation ceased after 8 days; moderately severe dwarf GA-deficient lines ls-1 and lh-1 had a 15% reduction in elongation rate but displayed no time-dependent slowing of the growth rate and brassinosteroid-insensitive and -deficient dwarfs lka and lkb showed slightly decreased root elongation. GA (levels reported in Yaxley et al. 2001 ) is not substantially limiting to root growth until it is severely deficient. The terminal 3 cm of roots of tall plants contained about 25 or 35 ng g−1 fresh weight indole-3-acetic acid (IAA), depending on the genetic background, and le-1 dwarfs were similar. Nana ( na-1 ) had less than 50% the level of IAA of tall, all the moderately severe dwarfs had reductions of about 30% and the slender plants had about 40% more IAA than the corresponding wild-type. With the exception of slender plants, IAA level in the root tips correlated with root elongation. Root growth seems to be promoted by IAA within the range of the internal concentrations detected. Nana plants had a reduced amount of IAA and a lower root-growth rate. Whereas external application of IAA always inhibits root growth, even at very low concentrations, root growth is not similarly inhibited by internal IAA as slender plants had the highest IAA level and growth rate similar to wild-type, regardless of the shoot GA content. 相似文献
11.
12.
In vitro oxidation of indoleacetic Acid by soluble auxin-oxidases and peroxidases from maize roots 总被引:7,自引:2,他引:7 下载免费PDF全文
Soluble auxin-oxidases were extracted from Zea mays L. cv LG11 apical root segments and partially separated from peroxidases (EC 1.11.1.7) by size-exclusion chromatography. Auxin-oxidases were resolved into one main peak corresponding to a molecular mass of 32.5 kilodaltons and a minor peak at 54.5 kilodaltons. Peroxidases were separated into at least four peaks, with molecular masses from 32.5 to 78 kilodaltons. In vitro activity of indoleacetic acid-oxidases was dependent on the presence of MnCl2 and p-coumaric acid. Compound(s) present in the crude extract and several synthetic auxin transport inhibitors (including 2,3,5-triiodobenzoic acid and N-1-naphthylphthalamic acid) inhibited auxin-oxidase activity, but had no effect on peroxidases. The products resulting from the in vitro enzymatic oxidation of [3H] indoleacetic acid were separated by HPLC and the major metabolite was found to cochromatograph with indol-3yl-methanol. 相似文献
13.
Comparative studies on tobacco pith and sweet potato root isoperoxidases in relation to injury, indoleacetic Acid, and ethylene effects 下载免费PDF全文
Sweet potato (Ipomoea batatas) root parenchyma and tobacco (Nicotiana tabacum) stem pith, both known to increase peroxidase activity after excision, differed from each other in their isoperoxidase patterns and in the isoperoxidase responses to injury and exogenous ethylene. 相似文献
14.
E. G. Rudikovskaya G. A. Fedorova L. V. Dudareva L. E. Makarova A. V. Rudikovskii 《Russian Journal of Plant Physiology》2008,55(5):712-715
It was shown that, in pea (Pisum sativum L.) roots, flavans are a dominating component of the soluble phenol fraction. In plants grown at low temperature (8°C), flavan content during the early growth phase was lower than in plants grown at 22°C, but later it increased and was by 40% higher than in plants grown at 22°C. Total phenol content in the two treatments differed insignificantly. Low growth temperature decreased the content of some phenolic compounds in pea seedling roots. 相似文献
15.
Interaction of indoleacetic Acid and gibberellic Acid in the short-term growth kinetics of oat stem segments 下载免费PDF全文
Gibberellins and auxins are the only hormones known that promote growth in oat (Avena sativa) stem segments, but when applied together, indoleacetic acid inhibits gibberellic acid-induced growth appreciably. This study shows that in addition to this inhibitory role, indoleacetic acid shortens the response time of the tissue to gibberellic acid. 相似文献
16.
Effects of ethylene and gibberellic Acid on cellular growth and development in apical and subapical regions of etiolated pea seedling 总被引:1,自引:0,他引:1 下载免费PDF全文
Subhook swelling of 4-day-old etiolated pea seedlings (var. Alaska), caused by 0.5 microliter per liter ethylene, was prevented by preincubation and continued growth in 0.1 mm gibberellic acid (GA). The subhook region exhibited normal elongation and cell size and volume. However, inhibition of elongation and cessation of cell division caused by 0.5 microliter per liter ethylene in the apical hook region of the etiolated pea stem were not overcome by GA. Most of the arrested cells were in G(2). These data suggest a possible interaction of GA and ethylene in cell enlargement in the subhook region of the etiolated pea seedlings. They also suggest a different mode of action by ethylene in the apical hook region where the ethylene effect was not counteracted by GA. 相似文献
17.
Subcellular fractions from pea (Pisum sativum L.) roots have been prepared by differential centrifugation techniques. Greater than 50% of the recovered plastids can be isolated by centrifugation at 500g for 5 minutes. Plastids of this fraction are largely free from mitochondrial and microsomal contamination as judged by marker enzyme analysis. De novo fatty acid biosynthesis in pea roots occurs in the plastids. Isolated pea root plastids are capable of fatty acid synthesis from acetate at rates up to 4.3 nanomoles per hour per milligram protein. ATP, bicarbonate, and either Mg2+ or Mn2+ are all absolutely required for activity. Coenzyme A at 0.5 millimolar improved activity by 60%. Reduced nucleotides were not essential but activity was greatest in the presence of 0.5 millimolar of both NADH and NADPH. The addition of 0.5 millimolar glycerol-3-phosphate increased activity by 25%. The in vitro and in vivo products of fatty acid synthesis from acetate were primarily palmitate, stearate, and oleate, the proportions of which were dependent on experimental treatments. Fatty acids synthesized by pea root plastids were recovered in primarily phosphatidic acid and diacylglycerol or as water soluble derivatives and the free acids. Lesser amounts were found in phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, and monogalactosyldiacylglycerol. 相似文献
18.
19.
Effects of gibberellic Acid, calcium, kinetic, and ethylene on growth and cell wall composition of pea epicotyls 下载免费PDF全文
Mondal MH 《Plant physiology》1975,56(5):622-625
The influence of gibberellic acid (GA), calcium, kinetin, and ethylene on growth and cell-wall composition of decapitated pea epicotyls (Pisum sativum L. var. Alaska) was investigated. Calcium, kinetin, and ethylene each caused an inhibition of GA-induced elongation of pea stems. Gibberellic acid did not reverse the induction of swelling by Ca2+, kinetin, or ethylene. Both Ca2+ and ethylene significantly inhibited the stimulatory effects of GA on the formation of residual wall material. Although GA promoted the development of walls relatively low in pectic substances and pectic uronic acid, Ca2+, kinetin, and ethylene favored the formation of walls rich in these constituents. Calcium, kinetin, and GA, alone or in combination, had no effect on the production of ethylene by pea epicotyls. 相似文献
20.
Although lateral roots may contribute significantly towards growth and nourishment of plants, the mechanics of their elongation behaviour in strong soils is not well known. The aim of this study is to report maximum axial growth pressures (p) and maximum elongation rates (E) of the lateral roots of an annual herbaceous plant (pea) and a woody perennial (eucalypt). As such measurements have not been reported previously, measurements of P and E for lateral roots were compared with the primary roots of pea for which reports are widespread. Values of P were estimated from the measured maximum values of axial force and root diameter on single, intact roots of seedlings in the laboratory. Additional measurements of both P and E were made for the lateral roots of pea when the growth of the remaining root axes was stopped (with removal of tips) to determine the overall effects of root-growth-inhibition on P and E of single roots.Values of P and E for lateral roots of pea were significantly greater than those for the lateral roots of eucalypt. Although root diameter for the primary roots of pea were similar to those for the lateral roots of eucalypt, the former exerted nearly twice as much pressure as the latter. The lateral roots of pea elongated significantly slower than the primary roots; however, P of lateral roots was significantly lower than the primary roots when elongation of all other roots was inhibited during the measurements. Production and/or development of lateral roots increased when elongation of the remaining roots (both primary and lateral roots) of pea seedlings was restricted due to the removal of root tips and exposure of one of the lateral roots to high strength. In general, maximum axial force exerted by primary and lateral roots was similar for roots of <1 mm diameter. However, primary roots exerted greater maximum axial force than the lateral roots when root diameter was >1 mm. As axial pressure of lateral roots was independent of root diameter, thickening of root tips is less likely to assist penetration of lateral roots in strong soils. 相似文献