Translocation of C<sup>14</sup> in Sugarcane

Hartt, Constance E.; Kortschak, Hugo P.; Forbes, Ada J.; Burr, George O.

doi:10.1104/pp.38.3.305

Cited by 80 publications

(42 citation statements)

References 24 publications

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“…A valuable featture of the castor beani system is that this fraction is large; as shown in figture 15, 80 % of the 14C absorbed from sucrose-'-C duiring a 30 minute ptulse moved otuit of the cotyledons dturing the suibsequent 8 and one-half hours. The velocity of translocation, rotughly 5 cm/hour is far below the highest rates reported (100-300 cm/hr) for example by Hartt et al (4) in stugar cane leaves and by \Vebb and Gorham (10) in sqtuash petiole, but is somewhat higher thail that observed in Salix stem (0.2-2.0 cm/hr) by Caniny-(2). Progressively larger amotunts of sucrose were absorbed at steady rates over several hours as the stucrose conicentration bathing the cotyledons was increased to as high a valuie as 0.5 M. There is e-vidence for saturation-of a low capacity absorption system at aboutt 0.1 m, and from the fact that removal of the embryonic axis abolished the capacity of the cotyledons to respond to higher concentratioins of stucrose we concluide that the lower capacity system represents tutilization within the cotyledons themselves as distinct from transfer into the translocatioun system.…”

Section: Methodsmentioning

confidence: 63%

Sugar Uptake and Translocation in the Castor Bean Seedling I. Characteristics of Transfer in Intact and Excised Seedlings

Kriedemann

Beevers

1967

Plant Physiol.

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Summary. Changes in the dry weights of variouis parts of the castor bean seedling showed that the rates of transfer of material through the cotyledons to the embryonic axis exceeded 2 mg/hour after 5 to 6 days of germination. The sugar present in the endosperm was predominantly, and in the cotyledon almost exclusively, sucrose. Anatomical features were described which contribute to the efficiency of the cotyledons as organs of absorption and transmittal of sucrose to the embryonic axis, where hexoses are much more prevalent.The ability of the cotyledons to absorb sucrose survived removal of the endosperm from the seedling. A series of experiments is described in which the cotyledons of such excised seedlings were immersed in sucrose-:"C and measurements made of uptake and of translocation to various parts of the seedling. Increasing rattes of absorption were observed as the sutcrose concentration was raised to 0.5 M and these rates were maintained for several hours. Removal of the embryonic axis (hypocotyl plus roots) drastically altered both the response to suicrose concentration and the time couirse of absorption by the cotyledons.More than 80 % of the stugar normally entering the cotyledons from the endosperm is transmitted to the embryonic axis and this extensive turnover was seen also in ptulse/chase experiments with excised seedlings. The cotyledons of excised seedlings absorbed sucrose against high apparent concentration gradients. The absorption was stimtulated by phosphate and had a pH optimtum at abolut pH 6.4. It was inhibited by arsenate, azide and 2,4-dinitrophenol.Previous work in this laboratory (1) has elucidated the pathway by which fat in the endosperm of the castor bean seedling is converted to carbohydrate during germination, but the means by which this sugar is introduced into the cotvledons and transported to the growing embryonic axis is unresolved. The cotyledons are specialized absorptive organs which are wholly responsible f')r the tuptake and transfer of the considerable sulbstrate requirements of the heterotrophic seedling. Materials and MethodsCastor beans (var. Cimmaron) wlere soakedl overnight at room temperature and germinated in moist vermicuilite in the dark at 300. For the growth stuldy, material was sampled from a large popuiliation of seedlings and dissected into endosperm (exclutding the ouiter integulments), cotvledons, and embryonic axis (hypocotyl and rtudimentary pluimule pluts roots). Fresh weights were determined and the tissuie was dried for 3 davs at 800 prior to measuiring dry weight.

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Section: Methodsmentioning

confidence: 63%

Sugar Uptake and Translocation in the Castor Bean Seedling I. Characteristics of Transfer in Intact and Excised Seedlings

Kriedemann

Beevers

1967

Plant Physiol.

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“…In sugarcane, translocationi takes l)lace b1 day and(l by night (11). The percentage of radioactivity tranislocated froml the fed blade is greater by day thain by night, and this differenice is miore conlspicUoUs wlhell the roots are miainitained at l1.7' than at 22.2°( 6, /7).…”

Section: Introductionmentioning

confidence: 98%

Light and Translocation of C¹⁴ in Detached Blades of Sugarcane

Hartt

1965

Plant Physiol.

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“…The primary member of this series, sucrose, is the most often reported translocated carbohydrate in plants (2). Raffinose appears in the sieve tube exudate of many species and is undoubtedly translocated (8).…”

Section: Introductionmentioning

confidence: 99%