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1.
Summary The reasons underlying the initial increase and subsequent decrease in the amount of radioactivity in the receiver block at the apical end of a Zea root segment supplied with a basal donor block containing labelled IAA have been investigated.The phenomenon was observed in segments supplied with IAA-1- 14C, IAA-2- 14C and IAA-5- 3H. An acropetal polarity in the movement of radioactivity into the receiver blocks was observed using donor blocks containing IAA-5- 3H at concentrations as low as 10 -10M.The decrease in the amount of radioactivity in the receiver block begins after 6–8 h of transport at 25° C, and is unaffected by renewal of the donor block every 2 h, or the presence of 2% sucrose in the donor and receiver blocks.The net export of radioactivity into the receiver block at the apical end of the segment virtually ceases after 6–8 h of transport at 25° C, and is not prolonged by the presence of 2% sucrose in the donor and receiver blocks. At 10° C, net export of radioactivity continues for at least the first 50 h of transport, and the amount of radioactivity in a continuously applied receiver block continues to increase over this period.Receiver blocks removed from the apical end of segments after 8 h of transport and placed on planchettes show little or no decrease in the amount of radioactivity they contain as a function of time, in marked contrast to those left in contact with the segment.There is a marked, and metabolically dependent, resorption of radioactivity from the receiver block at the apical end of the segment after about 8 h of transport at 25° C; most of the resorbed radioactivity remains in the apical 2–4 mm of the segment.There is a loss of radioactive CO 2 from segments supplied with a basal donor block containing 10 -6M IAA-1- 14C at 25° C, the emission beginning after 6–8 h of transport. Segments similarly supplied with 10 -6M IAA-2- 14C did not begin to lose radioactive CO 2 until after about 10–12 h of transport.The ability of the segments to transport radioactivity in a polar manner declines with time after they are excised from the root, regardless of whether their cut ends are kept in the intervening period in contact with plain agar blocks, or ones containing unlabelled IAA at 10 -6M. By the 6th h after excision at 25° C no transport of radioactivity through the segments and into the receiver blocks could be detected in either the aropetal or basipetal direction.The decrease in radioactivity in the receiver block after transport periods of 6–8 h at 25° C is therefore due to (1) a cessation of net export of radioactivity into the block, and (2) the onset of a metabolically-dependent, net resorption of radioactivity. At this time substantial amounts of radioactive CO 2 begin to be evolved from segments supplied with IAA-1- 14C, whereas with IAA-2- 14C radioactive CO 2 is not evolved for a further 4–6 h. 相似文献
2.
The movement of IAA- 14C through coleoptile segments of Avena and Zea has been investigated under aerobic and anaerobic conditions. The results are as follows: Zea. Using a 5-mm segment and a 2-hour transport period anaerobic conditions reduced the total uptake of 14C from an apical donor by 74% and the proportion of the total found in the receiving block by at least 45%. Anaerobic conditions reduced total uptake from a basal donor by 58% but no 14C reached the apical receiving block in either air or N 2. Uptake from apical and basal donor blocks in N 2 is closely similar. The presence of 14C in the basal receiving blocks, and its absence in the apical receiving blocks, in N2 suggests that even in anaerobic conditions movement of IAA is polarized basipetally, although the movement occurs at only a fraction of the rate found in air. Anaerobic conditions induced a similar reduction in basipetal movement of IAA in upper and lower 5-mm segments taken from the apical 10 mm of a Zea coleoptile. Using 10-mm Zea segments no 14C was recovered in the receiving blocks at the basal end of the segment after 2 and 4 hours in N2 whereas large amounts were recovered in air. Avena: Using 5-mm segments and a 2-hour transport period the total uptake of 14C from an apical donor is reduced by 83%. Movement of 14C into the basal donor is totally inhibited in N2. Total uptake of 14C from a basal donor is reduced by 61% in nitrogen and no 14C reached the apical receiving blocks regardless of the atmospheric conditions. A time course for the movement of 14C into the basal and apical receiving blocks through 5-mm segments showed that in air the amount in the basal receivers increased for 4 hours and then remained approximately uniform. In N2 no significant 14C reached the receivers until 6 to 8 hours after the application of donors but even then the amounts were about 12 to 14% of that in aerobic receivers. Movement of 14C into apical receivers was similar in air and in nitrogen and even after 6 to 8 hours the amount of radioactivity barely reached significant levels. 相似文献
3.
The movement of auxin through tendril segments of Passiflora caerulca L. has been investigated using IAA-2- 14C. It has been shown that (1) flux of IAA through the segments is strongly polarized basipetally: (2) the amount of 14C recovered in the basal receiver blocks increases linearly within a transport period of 6 h; (3) velocity of basipetal transport is 14.5 mm h ?1; (4) at least 70% of the radioactivity in the receiver blocks is confined to the IAA molecule: approximately 55% of 14C from methanolic extracts of the segments is IAA: (5) at low temperatures (2–4°C) the basipetal transport is abolished; (6) white light promotes basipetal transport, and this effect is abolished in a CO 2-free atmosphere; (7) no difference could be detected in 14C content between dorsal and ventral halves of tendril segments nor among individual dorsal and ventral receiver blocks. 相似文献
4.
Several experiments have been performed to analyse the ABA effects on the basipetal transport of IAA-2- 14C, using sections of epicotyls prepared from etiolated Lens seedlings. The sections were incubated in an ABA solution or ABA was applied in the donor blocks containing IAA. For each type of assay, the uptake (analyses of the donor blocks) and the movement of IAA-C 14 (analyses of the receiver blocks) were inhibited by ABA. The distribution of continuous decrease of the radioactivity, along the sections' axis, showed a 14C level from the apical towards the basal segments. ABA caused a decrease in the 14C concentration for the total sections, but a relative increase for the basal segment. When ABA was applied simultaneously with IAA in the donor blocks, the transport velocity of IAA, through the sections, was not changed significantly, while an ABA pretreatment caused a significant decrease. 相似文献
5.
Summary Movement of both [ 3H]GA 1 and [ 14C]GA 3 through root segments from P. coccineus seedlings was basipetally polarised. The basipetal/acropetal ratio of radioactivity from [ 3H]GA 1 in agar receiver blocks was 9.2 for apical, elongating segments, and 4.0 for more basal, non-elongating segments. Polarity of gibberellin transport was restricted to the stele, and absent from cortical tissues. Transport of [ 14C]IAA through root segments to agar receivers was preferentially acropetal, particularly so in the stele. Despite the existence of basipetal polarity of gibberellin transport in the root, [ 3H]GA 1 injected into cotyledons moved into and acropetally along the seedling root. 相似文献
6.
Transport and metabolism of IAA-1- 14C in Coleus blumei Benth. was studied by means of a combination of liquid scintillation counting, autoradiography and thin-layer chromatography. Transport of IAA in petiole segments of increasing age (No. 2-8) was strictly polar in a basipetal direction. No acropetal movement occurred in either young or old tissues. The greatest amount, expressed as a percentage of the radioactivity lost from the donor block, was found in basal receivers on petiole number 2. There was gradually less transport in older segments. The recovery as a percentage of the radioactivity not accounted for by donor and receiver blocks, measured by counting the radioactivity in an acetonitrile-extract of petiole segments, was low: 25 to 50%. In this acetonitrile-soluble fraction evidence for different radioactive compounds was found, depending on the age of the tissue. A possible relationship between the amounts of auxin transported in the tissue and its corresponding metabolism is discussed. 相似文献
7.
3H-IAA transport in excised sections of carnation cuttings was studied by using two receiver systems for recovery of transported
radioactivity: agar blocks (A) and wells containing a buffer solution (B). When receivers were periodically renewed, transport
continued for up to 8 h and ceased before 24 h. If receivers were not renewed, IAA transport decreased drastically due to
immobilization in the base of the sections. TIBA was as effective as NPA in inhibiting the basipetal transport irrespective
of the application site (the basal or the apical side of sections). The polarity of IAA transport was determined by measuring
the polar ratio (basipetal/acropetal) and the inhibition caused by TIBA or NPA. The polar ratio varied with receiver, whereas
the inhibition by TIBA or NPA was similar. Distribution of immobilized radioactivity along the sections after a transport
period of 24 h showed that the application of TIBA to the apical side or NPA to the basal side of sections, increased the
radioactivity in zones further from the application site, which agrees with a basipetal and acropetal movement of TIBA and
NPA, respectively. The existence of a slow acropetal movement of the inhibitor was confirmed by using 3H-NPA. From the results obtained, a methodological approach is proposed to measure the variations in polar auxin transport.
This method was used to investigate whether the variations in rooting observed during the cold storage of cuttings might be
related to changes in polar auxin transport. As the storage period increased, a decrease in intensity and polarity of auxin
transport occurred, which was accompanied by a delay in the formation and growth of adventitious roots, confirming the involvement
of polar auxin transport in supplying the auxin for rooting.
Received April 19, 1999; accepted December 2, 1999 相似文献
8.
Summary An acropetal polarisation of the movement of 2,4-dichlorophenoxy acetic acid (2,4-D) through subapical segments of Pisum seedling primary roots has been monitored throughout a 60 h transport period in darkness at 25° C using [1- 14C]2,4-D and [2- 14C]2,4-D. Uptake of 2,4-D does not proceed at a constant rate; periods in which the amount of 14C in the root segments and receiver blocks increases rapidly are followed by periods in which the amount of radioactivity remains relatively constant or declines slightly. These oscillations do not appear to be related to the time of day at which the experiments are begun or ended. Immobilisation and degradation of 2,4-D during transport in the segments seems to be low. Replacement of [1- 14C]2,4-D donor blocks after 25 h by blocks containing unlabelled 2,4-D results in continued transport of the compound into receiver blocks, with only small amounts of 14C remaining in the root tissues. Radioactivity is also exported from the segments into the blocks used to replace the donor blocks, with larger amounts being exported into the blocks applied to the apical ends than into those applied to the basal ends of the segments. This radioactivity may be taken-up again by the segments but more 14C is exported into these blocks towards the end of the experiments. The possibility of regular oscillations in uptake and movement of 2,4-D in Pisum root segments is discussed. 相似文献
9.
Several differences in the translocation pattern of radioactive kinetin in plant petioles were determined. Radioactivity from kinetin-8- 14C (Kn*) moved from donor agar blocks through petioles of bean and cocklebur but not of cotton. There was no difference in basipetal or acropetal movement of radioactivity from Kn* in cocklebnr petioles, but there was in bean petioles. In bean petioles this movement was preferentially basipetal, but it was influenced by the age of the petiole and by the presence of added indoleactic acid. The combination treatment accelerated the basipetal movement of radioactivity from Kn* in young bean petioles and not in old ones. All data is based on radioactivity translocated into receiver agar blocks which were assayed individually in a liquid scintillation spectrometer. The results show that plant species, direction of transport, age of tissue, and presence of IAA can all influence the translocation of Kn* in petioles. 相似文献
10.
The transport of radiolabeled indoleacetic acid (IAA), and some of its conjugates, was investigated in nodal stem segments of Phaseolus vulgaris L. Donor agar blocks containing either [2-acetyl- 14C]-IAA; [2-acetyl- 14C]-indole-3-acetyl-L-aspartate (IAAsp); [2-acetyl- 14C]-indole-3-acetyl-L-glycine (IAGly); or [2-acetyl- 14C]-indole-3-acetyl-L-alanine (IAAla) were placed on either the apical or basal cut surface of stem segments each bearing an axillary bud at the midline. In some experiments, a receiver block was placed on the end opposite to the donor. After transport was terminated, the segments were divided into five equal sections plus the bud, and the radioactivity of donors, receivers and each part of the stem segment was counted.For all four substances tested, the amount of 14C transported to the axillary bud from the base was the same or greater than that from the apical end. After basipetal transport, the distribution of 14C in the segment declined sharply from apex to base. The inverse was true for acropetal transport. Transport for the three IAA conjugates did not differ substantially from each other.The IAA transport inhibitor, N-1-naphthylphthalamic acid (NPA), inhibited basipetal 14C-IAA transport to the base of the stem segment but did not alter substantially the amount of 14C-IAA recovered from the bud. Transport of 14C-IAA from the apical end to all parts of the stem segment declined when the base of the section was treated with nonradioactive IAA. Taken together with data presented in the accompanying article [Tamas et al. (1989) Plant Growth Regul 8: 165–183], these results suggest that the transport of IAA plays a role in axillary bud growth regulation, but its effect does not depend on the accumulation of IAA in the axillary bud itself. 相似文献
11.
Jacobs, W. P., Beall, F. D. and Pharis, R. P. 1988. The transport and metabolism of gibberellins A 1 and A 5 in excised segments from internodes of Phaseolus coccineus. -Physiol. Plant. 72: 529–534. The transport and metabolism of gibberellins (GAs) ([ 3H]-GA, and [ 3H]-GA 5) of high specific radioactivity were investigated in excised segments from young internodes of Phaseolus coccineus L. Both GA 1 and GA 5 are native to this species and present in shoot tissue. The segments, 5.1 mm long, were incubated for 6 h in the horizontal position with agar donor blocks containing the [ 3H]-GA on the morphological apical or basal ends and with plain agar receiver blocks on the opposite end. At the end of incubation, the individual agar blocks were analyzed immediately for total radioactivity, or both blocks and intervening tissue were frozen and freeze-dried for later chromatographic analysis. The movement of both [ 3H]-GA, and [ 3H]-GA 5 was found to be consistently without polarity. However, approximately 5-fold more [ 3H]-GA, than [ 3H]-GA 5 was transported through the Phaseolus segments into receivers when equal amounts were in the donors. The extractable radioactivity from receiver blocks was primarily that of the donor GA. No putative GA conjugates were found in any class of receivers, but more GA metabolites were found in the free acid fraction from acropetal than basipetal receivers. Chromatographic analysis by reversed phase C 18 high performance liquid chromatography of the tissue segments showed that [ 3H]-GA, was metabolized more than [ 3H]-GA 5. Tissue adjacent to receiver blocks contained not only the precursor GA from the donor, but also polar ‘free GA metabolites’ and putative GA glucosyl conjugates. These results provide evidence that GA., which is the known ‘effector’ GA for elongation in shoot tissue of several species, is more effectively transported than GA 5 (a known precursor of GA 1) or than GA 1s more polar metabolites. 相似文献
12.
Summary Light promotes the net acropetal movement of 14C through 6-mm subapical segments of dark-grown roots of Zea mays supplied at their basal ends with 1 M IAA-1- 14C in agar blocks. This promotion occurs only when the segments are irradiated during the transport period, and both red and blue light appear to be as effective as white light at the radiant flux densities used in this investigation. The promotion is not found if the segments are pretreated with light and then returned to darkness before the trasport of IAA-1- 14C is determined. The very slight basipetal movement of 14C through the segments supplied with an apical source of IAA-1- 14C is unaffected by light.Only one radioactive substance is found in the apical receiver blocks. This substance has an R f virtually identical to those of the stock solution of IAA incorporated into the donor block and of unlabelled IAA. The movement of radioactivity into the receiver blocks through, the illuminated segments therefore appears to reflect the movement of IAA. Light thus increases the acropetal movement of IAA through the Zea root segment.The primary roots of Zea mays var. Giant Horse Tooth seedlings grown in total darkness do not exhibit a positive geotropic response. When the seed is orientated with the embryo uppermost the radicle grows out horizontally. On exposure to light, however, the roots bend down. This reaction appears about 3–9 hours after the onset of illumination, and white, red and blue light appear to be equally effective at the flux densities employed in this study. Green light in the spectral band between 510–530 nm did not appear to induce this positive geotropic responsiveness. 相似文献
13.
Summary When eight 14C-labelled auxin and non-auxin compounds were applied to the apical buds of intact dwarf pea seedlings ( Pisum sativum L.), only [1- 14C]indoleacetic acid ([ 14C]IAA) and -[1- 14C] naphthaleneacetic acid ([ 14C]NAA) underwent appreciable basipetal transport during the first 24 h; over a longer period (72 h) considerable basipetal transport of the auxin [1- 14C]2,4-dichlorophenoxyacetic acid ([ 14C]2,4-D) also occurred, but at a very much lower velocity ( ca. 1.4–2.2 mm·h -1). The movement of 2,4-D possessed many of the characteristics of a typical auxin transport. During uptake and transport IAA and NAA were extensively metabolised to the corresponding aspartates, and to ethanol-insoluble/NaOH-soluble compounds; little metabolism of 2,4-D was observed. None of the non-auxin compounds applied (sorbose, sucrose, leucine, adenine and kinetin) underwent appreciable basipetal transport from the apical bud. All but sorbose were extensively metabolised by the apical tissues. Little metabolism of sorbose itself was detected.The results suggest that the long-distance basipetal auxin transport system from the apical bud of intact plants is specific for auxins; the specificity may result from the affinity of auxins for specific transport sites. 相似文献
14.
Summary The net uptake and movement of radioactivity by 12-mm root segments of Zea mays have been studied as a function of time at 5, 15 and 25° C. Segments were supplied with an agar donor block containing 1 M IAA-1- 14C or IAA-2- 14C continuously or for a limited period of time (pulse-labelling). In the latter case the original donor block was replaced either by a plain agar block or by one containing 1 M unlabelled IAA. Receiver blocks were placed at the other end of the segments.The net uptake of radioactivity from the donor block at 15° C was greater at the basal end than at the apical end of the segment. At 5 and 15° C, the net uptake from a basal donor was virtually linear with time but at 25° C the rate of net accumulation decreased after about 10 h. Decarboxylation of IAA undoubtedly occurred at 15 and 25° C when the concentration in the tissue attained a high value.An acropetally polarised movement of radioactivity into the receiver blocks occurred regardless of whether the results were based on the actual amounts of radioactivity in the receiver block, or on the amounts in the receiver block expressed as a percentage of the net total radioactivity accumulated from the donor block. Only one radioactive substance was present in the receiver block and it ran to the same R f as IAA in the isopropanol: ammonium: water solvent system.The amounts of radioactivity moving into that part of the root segment at least 6 mm distant from the end in contact with either an apical or a basal donor block were assessed. An acropetal polarity in the movement of radioactivity was observed on the basis of the actual amounts of radioactivity in these distal parts of the segments, but no such polarity was evident when the amounts of radioactivity were expressed as a percentage of the net total accumulated from the donor block. At least 3 radioactive substances were present in the tissue in addition to the substance running to the same R f as IAA. The distribution of radioactivity in the segment cannot therefore be used to assess the distribution of IAA.Acropetal movement of radioactivity into an apical receiver block is not dependent upon the continued uptake of IAA at the basal end of the segment. No distinct pulses of radioactivity were detected moving through the root segments.Only a small part of the radioactivity in the root segment appears to be located in the polar transport system, while the bulk is not. The polarity found in the movement of the bulk radioactivity within the segment seems to be related to the polarity in IAA uptake from the donor blocks. 相似文献
15.
Summary The movement of 14C from indole-3-acetic acid (IAA) 14C has been examined in 5 mm root segments of dark-grown seedlings of Helianthus annuus and Brassica oleracea. Contaminants from distilled water, phosphate buffer and the razor-blade cutter increase the decarboxylation of IAA- 14C, and cutting of root segments results in an activation of IAA-destroying enzymes at the cut surfaces. When these sources of errors were eliminated the following was shown: a) Both in sunflower and cabbage there is a slight acropetal flux of 14C through the root segments into the agar receiver blocks. The amount of 14C found in the receiver blocks increases with the lenght of the transport period. b) When the root segments, after the transport period, are cut in two equal parts and these assayed separately, the amounts of 14C in the two parts indicate a greater acropetal than basipetal transport. c) The total radioactivity of the receiver blocks is in part due to IAA- 14C and in part to 14CO 2, the latter being a result of enzymatic destruction of auxin. d) Addition of ferulic acid, an inhibitor of IAA oxidases, to the receiver blocks markedly inhibits the decarboxylation of IAA- 14C and thus increases the amount transported. This effect is more pronounced after a 20 hr than after a 6 hr transport period. 相似文献
16.
Summary Movement of IAA was studied in excised coleoptile apices and whole seedlings of Zea mays L. and Avena sativa L. during geotropic stimulation. A micropipette technique permitted the application of [5- 3H]IAA at predetermined points on the coleoptiles with minimal tissue damage.When [5- 3H]IAA was applied to the upper side of a horizontal excised Zea coleoptile, about 60% of the recoverable radioactivity had moved into the lower half after 2 h. In contrast, when application was made to the lower side of a horizontal excised coleoptile, only 4% of the radioactivity migrated to the upper half. There was, thus, a net downward movement of 56%. Similar patterns of distribution were found for radioactivity in both the tissue and the basal receiver blocks. In horizontal shoot tissues of intact Zea seedlings a net downward movement of about 30% of the recoverable radioactivity occurred after 1 h of geotropic stimulation. Comparable experiments with Avena indicated a net downward movement of 6–12% in excised apices of coleoptiles and in the intact shoot. In both Zea and Avena chromatographic analyses of tissue and receiver blocks indicated that the movement of radioactivity reflected that of IAA.In Zea coleoptiles, the lateral migration of radioactivity after 2 h was 3 to 4 times greater in the apical tissues than in the basal tissues. A significant net downward movement of radioactivity was detected after 10 min of geotropic stimulation in the extreme apex of Zea coleoptiles but not in the more basal regions.These experiments show that downward lateral transport of IAA occurs in intact shoots of Zea and Avena seedlings upon geotropic stimulation. Lateral transport of IAA had previously been demonstrated only in sub-apical segments of Zea coleoptiles. 相似文献
17.
The rhizophore of Selaginella willdenovii Baker develops from the ventral angle meristem. The morphological nature of this organ has been in dispute. The purpose of this investigation was to obtain physiological evidence to support the contention that the rhizophore is a root and not a shoot. This was accomplished by studying the movement of 3H-indoleacetic acid and 14C-indoleacetic acid in Selaginella rhizophores. In 6-millimeter tissue segments, twice as much radioactivity accumulated in acropetal receivers as in basipetal. During 1 hour of transport in intact roots auxin traveled twice as far in the acropetal direction as basipetal. A significant amount of radioactivity transported in the tissue was found to co-chromatograph with cold indoleacetic acid. Decarboxylation accounted for 10% loss of activity from donors. The data provide sufficient physiological evidence that this organ is morphogenetically a root. 相似文献
18.
We examined the influence of aluminum and calcium (and certain other cations) on hormone transport in corn roots. When aluminum was applied unilaterally to the caps of 15 mm apical root sections the roots curved strongly away from the aluminum. When aluminum was applied unilaterally to the cap and 3H-indole-3-acetic acid was applied to the basal cut surface twice as much radioactivity (assumed to be IAA) accumulated on the concave side of the curved root as on the convex side. Auxin transport in the apical region of intact roots was preferentially basipetal, with a polarity (basipetal transport divided by acropetal transport) of 6.3. In decapped 5 mm apical root segments, auxin transport was acropetally polar (polarity = 0.63). Application of aluminum to the root cap strongly promoted acropetal transport of auxin reducing polarity from 6.3 to 2.1. Application of calcium to the root cap enhanced basipetal movement of auxin, increasing polarity from 6.3 to 7.6. Application of the calcium chelator, ethylene-glycol-bis-(β-aminoethylether)- N, N, N′, N′-tetraacetic acid, greatly decreased basipetal auxin movement, reducing polarity from 6.3 to 3.7. Transport of label after application of tritiated abscisic acid showed no polarity and was not affected by calcium or aluminum. The results indicate that the root cap is particularly important in maintaining basipetal polarity of auxin transport in primary roots of corn. The induction of root curvature by unilateral application of aluminum or calcium to root caps is likely to result from localized effects of these ions on auxin transport. The findings are discussed relative to the possible role of calcium redistribution in the gravitropic curvature of roots and the possibility of calmodulin involvement in the action of calcium and aluminum on auxin transport. 相似文献
19.
14C-Indoleacetic acid was applied to coleoptiles of corn ( Zea mays) and oat ( Avena sativa). The coleoptiles were detached from the endosperms at 6-minute intervals after indoleacetic acid application, and the radioactivity was determined in successive 2-millimeter regions. The rate (per cent per minute) of basipetal transport of indoleacetic acid is periodic in various regions of the coleoptile, with a period of about 20 minutes. The possible relation of this cyclic phenomenon to other rhythmic processes of similar periodicities is discussed. A distinct acropetal transport (against the concentration gradient) from the subapical region to the apical 2-millimeter region of the coleoptile was detected. 相似文献
20.
The effect of a 180° displacement from the normal vertical orientation on longitudinal growth and on the acropetal and basipetal movement of 14C-IAA was investigated in Avena sativa L. and Zea mays L. coleoptile sections. Inversion inhibits growth in intact sections (apex not removed) and in decapitated sections supplied apically with donor blocks containing auxin. Under aerobic conditions, inversion inhibits basipetal auxin movement and promotes acropetal auxin movement, whereas under anaerobic conditions, it does not influence the movement of auxin in either direction. Inversion retards the basipetal movement of the peak of a 30-minute pulse of auxin in corn. The inversion-induced inhibition of basipetal auxin movement is not explained by an effect of gravity on production, uptake, destruction, exit from sections, retention in tissue, or purely physical movement of auxin. It is concluded that inversion (a) inhibits basipetal transport, the component of auxin movement that is metabolically dependent, and as a result (b) inhibits growth and (c) promotes acropetal auxin movement. 相似文献
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