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1.
The metabolism of exogenously applied14C-24-epibrassinolide (14C-EBR) in seedlings of cucumber and wheat was examined. Total lipids were extracted with isopropanol and chloroform, and then
partitioned with water. More than 80% of radioactivity was distributed to chloroform-phase. Concentrated chloroform-phase
was applied to silica gel plate and was developed with chloroform-ethanol (5:1 v/v). Rf value of original14C-EBR was about 0.6. In cucumber leaves harvested after 2 day-culture, three peaks were detected at Rf 0.11, 0.47 and 0.84.
In cucumber petioles of 2 day-culture, however, a major peak was detected at Rf 0.90. But14C-EBR was hardly metabolized in hypocotyls and roots after 2 days.
In wheat leaves harvested just after pulse labeling, a peak was detected at Rf 0.63. By further analysis of this peak using
ODS-HPLC, however, an original peak of14C-EBR and two metabolites having higher polarity were detected. In wheat leaves harvested after 2 day-culture, the profile
of TLC scanning was similar to that just after pulse labeling, although, an original peak of14C-EBR was no longer detected by ODS-HPLC. In wheat roots,14C-EBR was hardly metabolized. These results indicate that14C-EBR occurring in leaves and petioles is metabolized to produce several kinds of metabolites. 相似文献
2.
Jasmonic acid (JA) is part of a long-distance signal-transduction pathway that effects increases in de-novo nicotine synthesis
in the roots of Nicotiana sylvestris Speg et Comes (Solanaceae) after leaf wounding. Elevated nicotine synthesis increases whole-plant nicotine pools and makes
plants more resistant to herbivores. Leaf wounding rapidly increases JA pools in damaged leaves, and after a 90-min delay,
root JA pools also increase. The systemic response in the roots could result from either: (i) the direct transport of JA from
wounded leaves, or (ii) JA synthesis or its release from conjugates in roots in response to a second, systemic signal. We
synthesized [2-14C]JA, and applied it to a single leaf in a quantity (189 μg) known to elicit both a whole-plant nicotine and root JA response
equivalent to that found in plants subjected to leaf wounding. We quantified radioactive material in JA, and in metabolites
both more and less polar than JA, from treated and untreated leaves and roots of plants in eight harvests after JA application.
[2-14C]Jasmonic acid was transported from treated leaves to roots at rates and in quantities equivalent to the wound-induced changes
in endogenous JA pools. The [2-14C]JA that had been transported to the roots declined at the same rate as endogenous JA pools in the roots of plants after
leaf wounding. Most of the labeled material applied to leaves was metabolized or otherwise immobilized at the application
site, and the levels of [2-14C]JA in untreated leaves did not increase over time. We measured the free JA pools before and after four different hydrolytic
extractions of root and shoot tissues to estimate the size of the potential JA conjugate pools, and found them to be 10% or
less of the free JA pool. We conclude that the direct transport of wound-induced JA from leaves to roots can account for the
systemic increase in root JA pools after leaf wounding, and that metabolism into less polar structures determines the duration
of this systemic increase. However, the conclusive falsification of this hypothesis will require the suppression of all other
signalling pathways which could have shoot-to-root transport kinetics similar to that of endogenous JA.
Received: 14 April 1997 / Accepted: 9 June 1997 相似文献
3.
The effects of 24-epibrassinolide (EBR) added to nutrient solution on growth of cucumber (Cucumis sativus L.) under root-zone hypoxia were investigated. Cucumber seedlings were hydroponically grown for 8 days in normoxic and hypoxic
nutrient solutions with and without addition of EBR at 1 μg l−1. EBR exerted little influence on plant performance in the normoxic nutrient solution, while the chemical alleviated root-zone
hypoxia-induced inhibition of root and shoot growth and net photosynthetic rate (Pn). EBR added to hypoxic nutrient solution
caused an increase in the concentration of fructose, sucrose, and total soluble sugars in the roots but not in the leaves.
Root-zone hypoxia enhanced the activities of lactate dehydrogenase (LDH), alcohol dehydrogenase (ADH), and pyruvate decarboxylase
in the roots. Interestingly, EBR further enhanced ADH activity but lowered LDH activity in hypoxic roots. These results suggest
that EBR added to hypoxic nutrient solution may stimulate the photosynthate allocation down to roots and the shift from lactate
fermentation to alcohol fermentation in hypoxic roots, resulting in the increase in ATP production through glycolysis and
the avoidance of cytosolic acidosis and eventually enhanced tolerance of cucumber plants to root-zone hypoxia. 相似文献
4.
W. Jiang P.C. Struik J. Lingna H. van Keulen Z. Ming & T.J. Stomph 《The Annals of applied biology》2007,150(3):383-391
We investigated the uptake and distribution of zinc (Zn) either applied to the roots or to the leaves in rice during grain development. Plants of two aerobic rice cultivars were grown in a nutrient solution with either sufficient Zn or surplus Zn. Root treatment with 1 week‘s supply of both 65Zn and unlabelled Zn was started at flowering or 15 days after flowering (DAF). Foliar treatment with 65Zn applied to the flag leaf or to senescent leaves was carried out at flowering. When 65Zn was applied to roots, plants continued to take up Zn after flowering, even beyond 15 DAF, irrespective of cultivar and Zn nutritional status of the plants. During the 1 week of supply of both 65Zn and unlabelled Zn, which either started at flowering or 15 DAF, the absorbed 65Zn was mainly distributed to roots, stem and grains. Little 65Zn was allocated to the leaves. Following a week of 65Zn supply directly after flowering, under sufficient Zn or surplus Zn, the proportions of total 65Zn uptake allocated to the grains continued to change during grain filling (9–33%). This Zn mainly came from the roots but under sufficient Zn supply also from the stem. With 65Zn applied to leaves (either the flag leaf or the lowest senescent leaf), both cultivars showed similar Zn distribution within the plants. About 45–50% of the 65Zn absorbed was transported out of the 65Zn‐treated leaf. From that Zn, more than 90% was translocated to other vegetative organs; little was partitioned to the panicle parts and even less to the grains. These results suggest that in rice plants grown under sufficient or surplus Zn supply, most of the Zn accumulated in the grains originates from uptake by roots after flowering and not from Zn remobilisation from leaves. 相似文献
5.
Maurice Arissian Dominique Perrissin-Fabert André Blouet Jean-Louis Morel Armand Guckert 《Journal of Plant Growth Regulation》1991,10(1-4):1-4
The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)14C-chlormequat chloride, (2) CYCOCEL* CL containing14C-chlormequat chloride, and (3) CYCOCEL* CL containing14C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the14C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant. 相似文献
6.
Maurice Arissian Dominique Perrissin-Fabert André Blouet Jean-Louis Morel Armand Guckert 《Journal of Plant Growth Regulation》1991,10(1):1-4
The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)14C-chlormequat chloride, (2) CYCOCEL* CL containing14C-chlormequat chloride, and (3) CYCOCEL* CL containing14C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the14C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant. 相似文献
7.
Summary Uniformly14C labelled glucose, cellulose and wheat straw and specifically14C labelled lignin component in corn stalks were aerobically incubated for 12 weeks in a chernozem soil alongwith15N labelled ammonium sulphate. Glucose was most readily decomposed, followed in order by cellulose, wheat straw and corn stalk lignins labelled at methoxyl-, side chain 2-and ring-C. More than 50% of14C applied as glucose, cellulose and wheat straw evolved as CO2 during the first week. Lignin however, decomposed relatively slowly. A higher proportion of14C was transformed into microbial biomass whereas lignins contributed a little to this fraction.After 12 weeks of incubation nearly 60% of the lignin14C was found in humic compounds of which more than 70% was resistant to hydrolysis with 6N HCl. Maximum incorporation of15N in humic compounds was observed in cellulose amended soil. However, in this case more than 80% of the15N was in hydrolysable forms.Immobilization-remineralization of applied15N was most rapid in glucose treated soil and a complete immobilization followed by remineralization was observed after 3 days. The process was much slow in soil treated with cellulose, wheat straw or corn stalks. More than 70% of the newly immobilized N was in hydrolysable forms mainly reepresenting the microbial component.Serial hydrolysis of soil at different incubation intervals showed a greater proportion of 6N HCl hydrolysable14C and15N in fractions representing microbial material.14C from lignin carbons was relatively more uniformly distributed in different fractions as compared to glucose, cellulose and wheat straw where a major portion of14C was in easily hydrolysable fractions. 相似文献
8.
Labelled carbon dioxide was supplied for 22 hrs to a leaf of the leader or to the lateral shoot in two-year-old apple seedlings. The distribution of radioactive assimilates within the plant following this treatment was investigated by using radioautography. The transport of labelled assimilates from the young leaf of the leader was very meagre and affected only parts of the stem and the leaves situated in the close vicinity of the treated leaf. The14C-labelled assimilates from the mature leaf of the leader were transported in a considerable amount to the apex and to the other leaves of the leader. They were also found in an appreciable amount in the stem and the roots, as well as in some lateral shoots. After supplying14CO2 to the lateral shoot remarkable transport of labelled assimilates was observed. Radioactivity was detected in the tip and in the youngest leaves of the leader, as well as in the roots. Their path in the stem was studied by dissecting the plant and examining the cross section from each internode. This method revealed that the assimilates from the treated leaf or shoot were transported downward only on one side of the stem in a helical pattern. The lateral shoots situated on the radioactive side of the stem were also labelled, whereas those situated on the opposite (non-radioactive) side were not labelled. 相似文献
9.
6(5)carboxyfluorescein (6(5)CF), a polar fluorescein with an apparent pK of 6.3, was introduced, as a pH 6.3 solution, into the apoplast of lamina or petioles of mature soybean leaves. Freehand sections were prepared at various times and immediately observed with a fluorescence microscope. 6(5)CF-associated fluorescence appeared in all sink organs, from shoot apex to roots. It was strictly confined to the phloem regions, even after 4 days. Its transport into young leaves ceased at approximately the time they underwent sink-to-source transition. It was never transported between two leaflets of the same leaf. Its transport was interrupted by phloem destruction. All these transport characteristics were highly reproducible, and were paralleled by those of 14C transport after application of (14C)sucrose to leaf surfaces. In contrast with 6(5)CF, fluorescein was transported between mature leaves, and between leaflets of the same leaf. It was not restricted to phloem, and often appeared in the xylem region. These results indicate that 6(5)CF can be used to monitor phloem sap translocation in real time, in short- and long-term experiments. 相似文献
10.
The uptake and distribution of eight metallic elements were examined in wheat seedlings for a period of 12 d with a radioactive
multitracer technique. The radioactive nuclides of the seedlings were simultaneously determined by γ-ray spectrometry. All
of the elements studied were taken up by the wheat seedlings and mainly accumulated in the roots. Only some elements were
transported to shoots and leaves of the seedlings or bound to leaf proteins, and two elements were transported into the chloroplast.
Uptake of most elements reached a maximum on the fifth or the eighth day and then gradually decreased afterward. In the cases
of 95mTc and 72Se, the uptake increased continuously within 12 d without the peak uptake. The change of elemental concentrations was dependent
on uptake and excretion rates. The dynamics of metal elements taken up by the wheat seedlings and their distribution in roots,
shoots, and leaves were different for each element, suggesting that it may depend on the characteristics of the elements. 相似文献
11.
Chlormequat chloride labelled with 14C was applied to the thirdleaf of Proctor barley and Maris Dove wheat; after 1 d lessthan a fifth could be washed off with water. More 14C-labelledmaterial moved from treated areas of wheat than of barley toaccumulate in tips of treated leaves, younger main-stem leaves,main stems, and ears. Relatively small amounts of radioactivematerial accumulated in roots, but less in wheat than barley.About 80% of the radioactivity was recovered from plants upto 1 week after application, but the amounts recovered in aqueouswashings and extracts decreased faster from wheat than frombarley. 相似文献
12.
This study evaluated effects of foliar spraying 24‐epibrassinoide (24‐EBL) on the growth of salt‐stressed canola. Seedlings at the four‐leaf stage were treated with 150 mm NaCl and different concentrations of 24‐EBL (10?6, 10?8, 10?10, 10?12 m ) for 15 days. A concentration of 10?10 m 24‐EBL was chosen as optimal and used in a subsequent experiment on plant biomass and leaf water potential parameters. The results showed that 24‐EBL mainly promoted shoot growth of salt‐stressed plants and also ameliorated leaf water status. Foliar spraying of salt‐stressed canola with 24‐EBL increased osmotic adjustment ability in all organs, especially in younger leaves and roots. This was mainly due to an increase of free amino acid content in upper leaves, soluble sugars in middle leaves, organic acids and proline in lower leaves, all of these compounds in roots, as well as essential inorganic ions. Na+ and Cl? sharply increased in different organs under salt stress, and 24‐EBL reduced their accumulation. 24‐EBL improved the uptake of K+, Ca2+, Mg2+ and NO3? in roots, which were mainly transported to upper leaves, while NO3? was mainly transported to middle leaves. Thus, 24‐EBL improvements in ion homeostasis of K+/Na+, Ca2+/Na+, Mg2+/Na+ and NO3?/Cl?, especially in younger leaves and roots, could be explained. As most important parts, younger leaves and roots were the main organs protected by 24‐EBL via improvement in osmotic adjustment ability and ion homeostasis. Further, physiological status of growth of salt‐stressed canola was ameliorated after 24‐EBL treatment. 相似文献
13.
G. J. A. RYLE 《The Annals of applied biology》1970,66(1):155-167
The movement of 14C-labelled assimilate to the terminal meristem, stem, mature leaves, tillers and roots was measured in Loliurn perenn and Lolium temulentum after exposure to 14C02 of the youngest fully-expanded leaf and, on fewer occasions, the oldest healthy leaf on the main shoot. During early vegetative growth, the terminal meristem, tillers and roots received most of the 14C exported from the youngest leaf. As the shoot aged, more 14C was exported to the terminal meristem and tillers and less to roots. When the stem became a sizeable sink for 14C at the six-leaf (L. temulentum) or eleven-leaf (L. perenne) stage, less 14C moved to tillers and much less to roots. The terminal meristem continued to receive 14 at a steady rate throughout late vegetative growth. The transition from vegetative to reproductive growth in both species was marked by an abrupt increase in the export of 14C to stem from the upper leaf, but there was little change in the proportion of 14C which moved to the developing leaves and incipient inflorescence at the terminal meristem. At the same time, less 14C moved to tillers and much less to roots. Immediately before ear emergence, the export of 14C from the upper leaf (flag leaf) to the stem declined and the proportion moving to the ear increased, reaching a maximum of 55–75% as the ear emerged. The relative patterns of export of upper and lower leaves showed that while some 14 moved from each leaf to all meristems, the proximity of actively growing meristems appeared to be the main factor which determined the destination of most exported 14C. The distribution of 14C from upper and lower leaves was most alike in young vegetative plants of L. perenne. At later stages of development of both species, the terminal meristem and stem received most 1414C from the upper leaf, while roots and tillers received mos 1414C from the oldest leaf at the base of the shoot. 相似文献
14.
Distribution and mobility of manganese in the hyperaccumulator plant Phytolacca acinosa Roxb. (Phytolaccaceae) 总被引:2,自引:0,他引:2
Xianghua Xu Jiyan Shi Yingxu Chen Xincai Chen Hui Wang Anton Perera 《Plant and Soil》2006,285(1-2):323-331
The distribution and mobility of manganese (Mn) in the hyperaccumulator plant species Phytolacca acinosa Roxb. (Phytolaccaceae) were investigated in a hydroponic system. The plants were exposed to 2 or 5 mM Mn for up to 28 days. For any given plant, the Mn content in the mature leaves (nos. 5–9) was always higher than that in the old (nos. 1–4) and young leaves (nos. 10–14). Within the different parts of a leaf, Mn was preferentially accumulated in the leaf marginal area, where the observed level was threefold higher than that in the midrib. Cross-sectional analysis of the leaf revealed that the concentration of Mn was higher in the leaf epidermis than in the mesophyll. Cell fractionation analysis with P. acinosa leaves showed that most of the Mn (78.4%) was present in the final supernatant fraction (following centrifugation at 20,000 g for 45 min). The distribution of Mn in the leaves of P. acinosa was controlled mainly by the transpiration rate. Our investigation demonstrated that Mn was readily transported from the roots to shoots of P. acinosa but that it could not be remobilized readily after it reached leaves. 相似文献
15.
An inhibition of photosynthetic electron transport in susceptible rye following treatment with DDT is accompanied by an increase in dry weight of leaves contacting the pesticide due to an accumulation of fructose, glucose, and to lesser extent, sucrose. Several days after treatment over 40% of the dry weight is due to these sugars. The assimilation of 14CO2 by leaf segments was decreased as a consequence of DDT treatment, but labelling patterns were similar to those for leaf segments from untreated plants. However, if given a prolonged period in darkness before extraction of assimilates the leaf segments from treated seedlings retained 14C in sugars and did not show the substantial decrease in extractable soluble material which was characteristic of untreated controls. In DDT-treated seedlings the translocation of metabolites from leaves to roots was severely impaired. 相似文献
16.
N. O. Adedipe 《Biologia Plantarum》1975,17(3):161-166
In controlled environment growth chambers, the effects of foliar and root applications of 2-chloroethyltrimethylammonium chloride (CCC) and 2,4-dichlorobenzyltributylphosphonium chloride (Phosfon) on the translocation of32P fed to leaves, were investigated. When applied to leaves or to root, CCC had no effect on the relative amounts of32P radioactivity retained by the fed leaf 5, 20 and 80 h after feeding. At 20 and 80 h after feeding, Phosfon concentrations of 0.01 and 0.1mg l?1 reduced retention of the applied32P. 80 h after32P feeding, CCC concentration of 1 mg l?1 applied as a foliar spray or to the root enhanced the downward movement of32P. Phosfon at low concentrations, particularly at 0.1 mg l?1, on the other hand, favoured an upward transport of the applied32P. Foliar applications of CCC and Phosfon at high concentrations had no significant effect on32P transport to the root and the shoot below the fed leaf, while root applications of CCC and of Phosfon inhibited downward transport. Root applications generally caused greater alterations in32P distribution patterns than did foliar applications. On the basis of total active ingredient uptake, Phosfon was more effective than CCC in altering translocation patterns. 相似文献
17.
ULF HALLMÉN 《Physiologia plantarum》1974,32(1):78-83
Uptake, translocation and complex formation of 14C-labelled 4-amino-3,5,6-trichloropicolinic acid (picloram) and 2,4-dichlorophenoxyacetic acid (2,4-D) in seedlings of rape (Brassica napus L. cv. Nilla) and sunflower (Helianthus annuus L. var. uniflorus) were studied. Sunflower is susceptible both to 2,4-D and picloram, while rape is susceptible to 2,4-D but more tolerant to picloram. The uptake of the herbicides through the leaves was almost complete in both species. Translocation of 2,4-D into the roots took place more readily than that of picloram. In sunflower about 50 per cent of the applied 2,4-D was extruded through the roots into the nutrient solution after 9 days. In the picloram-treated sunflower most of the activity was found in the aerial parts, while in picloram-treated rape most of the activity still occurred in the treated leaf after 9 days. No activity at all was found in the roots or in the nutrient solution of the picloram-treated rape seedlings. While the major part of 2,4-D always was found in the state of free herbicide, a large fraction of picloram was rapidly bound into water-soluble complexes. This binding was especially pronounced in rape. Separation by paper chromatography showed that different radioactive compounds were formed. Most of these could be hydrolyzed, thereby releasing free herbicide. The results support the hypotheses that complex formation could counteract herbicide translocation and toxicity of auxin herbicides. 相似文献
18.
Acyl lipids and pigments were analyzed in young plants of garden pea, spring wheat and spinach exposed to < 5 or 65 nl l?1 ozone 12 h per day for 6 days. In one set of experiments, the plants were exposed to 14CO2 for 2 h 3 days prior to ozone exposure. The plants responded differently to the moderately enhanced level of ozone used Spinach was not at all sensitive while in both pea and wheat, leaves of different ages differed in ozone sensitivity. In pea, ozone sensitivity increased with leaf age. In the second and third oldest leaves, the amounts of galactolipids per leaf area and the proportions of 18:3 of the total lipid extract and of phosphatidylglycerol decreased. In the second oldest leaf, ozone also caused a decreased proportion of 18:3 of monogalactosyldiacylglycerol. In the fourth oldest leaf, lipid composition and galactolipid unsaturation was unaffected, but ozone caused decreased leaf expansion resulting in increased acyl lipid content per leaf area. In both the first and second leaves of wheat, ozone fumigation caused a marked decrease in the content of monogalactosyldiacylglycerol and in the first leaf, the contents of phosphatidylcholine and phosphatidylethanolamine increased. The proportion of 18:3 in phosphatidylcholine was larger in ozone-fumigated than in control plants, while the reverse applied for phosphatidylglycerol. In the oldest sampled leaves of pea and wheat, ozone caused an increase in the radioactivity associated with β-carotene, indicating increased turnover. Thus, while spinach was unaffected, in both pea and wheat ozone caused a decrease in the proportion of chloroplast membrane lipids to non-chloroplast membrane lipids in older leaves while younger leaves were less sensitive. 相似文献
19.
O. H. D. MAKUNGA I. PEARMAN S. M. THOMAS G. N. THORNE 《The Annals of applied biology》1978,88(3):429-437
In 2 years the distribution of radioactivity recovered in entire shoots of field-grown winter wheat was determined at various times after exposing the top two leaves (flag leaf or second leaf) to 14CO2 for 30 s. In 1976 when 14C was supplied to either leaf 14 days before anthesis, 30% was in the ear at anthesis. Less than 5% was in the leaf exposed to I4CO2. The remainder was equally divided between the stem above and below the flag-leaf node when the flag leaf had been exposed, and was mainly in the lower part of the stem when the second leaf had been exposed. By maturity the proportion in the stem had decreased; 20% of the total activity was in the grain and 30% was still in the ear structures. When 14C was supplied 10 days after anthesis, the proportion in the ear 24 h later ranged from 42 to 69% of that in the whole shoot when the flag leaf was exposed, and from 6 to 28% when the second leaf was exposed. At maturity these proportions increased to 92 and 85% when the 14C had been supplied to flag leaves and second leaves respectively. When 14C was supplied 25 days after anthesis to either flag leaves or second leaves, more than 90% of the activity was in the mature ears. Less than 5% of the 14C remaining at maturity from any treatment was still in the leaf exposed to 14CO2. Between 2 and 6% of 14C supplied after anthesis was in the non-grain parts of the ear. The proportion of the 14C in the ear was greatest for the semi-dwarf varieties Maris Fundin and Hobbit, less for Maris Huntsman, and least for Cappelle-Desprez. These varietal differences were large 24 h after exposure to 14CO2, especially in 1976. They were small and rarely significant at maturity. Nitrogen fertiliser up to 210 kg N ha-1 had negligible effects on the distribution of 14C, although it greatly increased growth and yield, especially in 1975. 相似文献
20.
The biosynthesis of 14C-IAA from 14C-tryptophan applied to abraded leaves of Ricinus communis and its subsequent export through the phloem were studied. Phloem sap was collected at intervals from incisions made in the stem below the IAA fed leaf. Any upward movement of label through the phloem or downward movement of phloem mobile compounds from leaves above the treated one were restricted by bark-ringing the plants.TLC and HPLC analyses of the collected sap indicate that some conversion of 14C-tryptophan to 14C-IAA had occurred. Subsequent GC-MS analysis of the HPLC purified samples of phloem sap revealed high levels of endogenous IAA transported from the fed leaf. The high ratio of unlabelled/labelled IAA in the phloem sap makes unequivocal confirmation by GC-MS of the predicted biosynthesis of 14C-IAA impossible. It is postulated that IAA is synthesised from tryptophan in mature leaves and exported to developing sink tissues with the flow of photoassimilates in the phloem. 相似文献