A Technique for Collection of Exudate from Pea Seedlings

Hanson, Susan D.; Cohen, Jerry D.

doi:10.1104/pp.78.4.734

Cited by 15 publications

(6 citation statements)

References 15 publications

(13 reference statements)

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“…1), as reported also for exudation sap from the hypocotyl of Ricinus communw (Kallarackal et al 1989). A possible source of sucrose exuded is the phloem (Hanson and Cohen 1985). As reported by Haoson and Cohen (1985), sucrose exudation from the pea epicotyl did not occur in the absence of EDTA (Fig.…”

Section: Discussionsupporting

confidence: 78%

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Sugar accumulation in growing subhooks of etiolated Pisum sativum seedlings - Stimulation of sugar exudation and invertase activity in epicotyls by gibberellic acid

Miyamoto¹,

Ueda²,

Kamisaka³

1992

Physiol Plant

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S. 1992. Sugar accumulation in growing subhooks o£ etiolated Pisum sativum seedlings -Stimulation of sugar exudation and invertase activity in epicotyls by gibberellic acid. -Pbysiol. Plant. 84: 106-112.The epicotyl of 5-day-old derooted cuttings of pea (Pisum sativum L. cv. Alaska) with and without cotyledons exuded sucrose and glucose in the presence of EDTA. The amount of sugars exuded was greatly affected by the position at which the epicotyl was cut. The largest amount of sugars was exuded when the epicotyl was cut 2 mm below the hook, leaving the growing subhook. Gibberellic acid (GA) substantially increased the amount of sugars exuded from the epicotyl in the presence of cotyledons but only slightly in their absence. GA stimulated sugar exudation from the cotyledonary node as well as from the epicotyl. In cuttings with cotyledons. GA enhanced invertase activity in the apoptast, and in the intracellular soluble and bound fractions in the growing subhook. In decotylized cuttings, GA enhanced only soluble invertase activity. GA did not affect invertase activity in the epicotyl below the subhook. These results suggest that GA stimulates sugar accumulation in the growing subhook by stimulating not only phloem loading of sucrose in the cotyledons but also unloading in the subhook.

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Section: Discussionsupporting

confidence: 78%

“…The vascular exudate from pea epicotyls was collected according, to the method of Hanson and Cohen (1985) (Fig. 1).…”

Section: Vascular Exudation Of Sugarsmentioning

confidence: 99%

Sugar accumulation in growing subhooks of etiolated Pisum sativum seedlings - Stimulation of sugar exudation and invertase activity in epicotyls by gibberellic acid

Miyamoto¹,

Ueda²,

Kamisaka³

1992

Physiol Plant

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“…Several previous reports on the levels of free TRP in plant material have given a range of values from 1 to 500 uM (9,16,28,29), with the highest values found in seed material. Growing vegetative parts ofthe plant usually contain between 1 and 10 gM free TRP (9,14), and such levels are consistent jsR.…”

Section: Discussionmentioning

confidence: 99%

“…The TRP peak was streaked on a second TLC plate and eluted as above. Endogenous TRP Extractions from Lemna TRP was extracted from Lemna (PL and jsR1) by previously published methods with only slight variation, and then quantified by isotope dilution analysis (15,16). Plant material, 1 or 2 g for L-TRP extractions or at least 20 g for D-TRP extractions, was frozen in liquid nitrogen and homogenized in 70% acetone (5 mL/g of tissue).…”

Section: Plantmentioning

confidence: 99%

Stable Isotope Labeling, in Vivo, of d- and l-Tryptophan Pools in Lemna gibba and the Low Incorporation of Label into Indole-3-Acetic Acid

Baldi¹,

Maher²,

Slovin³

et al. 1991

Plant Physiol.

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We present evidence that the role of tryptophan and other potential intermediates in the pathways that could lead to indole derivatives needs to be reexamined. Two lines of Lemna gibba were tested for uptake of [15N-indole]-labeled tryptophan isomers and incorporation of that label into free indole-3-acetic acid (IAA). Both lines required levels of L-['5Njtryptophan 2 to 3 orders of magnitude over endogenous levels in order to obtain measurable incorporation of label into IAA. Labeled L-tryptophan was extract-able from plant tissue after feeding and showed no measurable isomerization into D-tryptophan. D-['5N]tryptophan supplied to Lemna at rates of approximately 400 times excess of endogenous D-tryptophan levels (to yield an isotopic enrichment equal to that which allowed detection of the incorporation of L-tryptophan into IAA), did not result in measurable incorporation of label into free IAA. These results demonstrate that L-tryptophan is a more direct precursor to IAA than the D isomer and suggest (a) that the availability of tryptophan in vivo is not a limiting factor in the biosynthesis of IAA, thus implying that other regulatory mechanisms are in operation and (b) that L-tryptophan also may not be a primary precursor to IAA in plants. Many studies of IAA biosynthesis have shown that TRP4 is the primary precursor of IAA by one of several different pathways (for reviews, see refs. 1, 24). However, studies of in vivo biosynthesis ofIAA in maize seedlings have demonstrated that conversion of TRP to IAA does not occur at significant rates (9, 17, 21). The simple model for TRP involvement in IAA biosynthesis is further complicated by the natural occurrence of the 12 carbon indole, IBA, in some plant tissues (8, ' 3Present address: USDA/ARS Plant Hormone Laboratory, Belts-ville, MD 20705. 4Abbreviations: TRP, tryptophan; IBA, indole-3-butyric acid; PL, parental line; GC-MS-SIM, selected ion monitoring GC-MS; DIP-MS, direct insertion probe-MS; El, electron impact. 1203 23). The metabolic conversion of an indolic precursor to IBA has not been demonstrated; however, the side chain reduction of IBA to IAA has been shown to occur in plants (10, 12). These results present an interesting problem with respect to the hypothesis that TRP is the primary precursor to indoleal-kanoic acids in plants. The in vivo role of TRP and other potential intermediates in pathways that could lead to indole derivatives clearly needs to be reexamined. Recently, D-TRP, rather than the much more abundant L isomer, has been proposed to be a direct biosynthetic precursor of IAA based on evidence of gibberellin enhanced race-mization of L-TRP to D-TRP, which could then be transa-minated to indolepyruvic acid (19, 20). The evidence for the in vivo operation of this pathway is difficult to interpret because correction of the specific activity of the applied labeled compounds, necessitated by the differences in uptake and size of internal pools, was not done. Our studies of IAA biosynthesis in vivo have been facilitated by the use of an IAA overp...

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“…Phloem exudate from apical shoots was obtained using the EDTA exudation technique (King and Zeevaart, 1974;Hanson and Cohen, 1985). Pea apex explants, including the youngest unexpanded leaf and 2 cm of the internode immediately below the leaf, were made when the first flower was at anthesis.…”

Section: Methodsmentioning

confidence: 99%