Translocation of 14Carbon in Tobacco following Assimilation of 14Carbon Dioxide by a Single Leaf

Jones, Harriet; Martín, R. V.; Porter, H. K.

doi:10.1093/oxfordjournals.aob.a083673

Cited by 99 publications

(112 citation statements)

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“…The presence of DNP in the medium around the cotyledons during the initial pulse and the following chase had 2 pronounced effects on the uptake and translocation profile. (3,6,9,10). 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.…”

Section: Methodsmentioning

confidence: 99%

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: 99%

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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“…A very precise pattern of movement of labelled assimilate from a source leaf upward into other fully expanded leaves has been described by Jones, Martin and Porter (1959) and by Joy (1964). Many other workers have stressed the lack of movement of assimilate into any but actively growing young organs or developing reproductive parts.…”

Section: Introductionmentioning

confidence: 93%

Translocation Into Mature Leaves–the Effect of Growth Pattern

Thrower

1977

New Phytologist

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“…It has been shown that a leaf during its ontogeny functions first as a metabolic sink and later, before it has expanded to its final size, as a metabolic source (3,12,17 by factors in other parts of the plant? How is this shift related to intensity of photosynthesis and composition of the metabolites?…”

Section: Introductionmentioning

confidence: 99%

Translocation and Metabolic Conversion of ¹⁴C-Labeled Assimilates in Detached and Attached Leaves of Phaseolus vulgaris L. in Different Phases of Leaf Expansion

Köcher

Leonard

1971

Plant Physiol.

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Leaf excision greatly affected the actual levels of "C-assimilates in laminas and petioles of primary bean leaves (Phaseolus vulgaris L.) following a transport period. However, it did not affect the percentage of starch in the insoluble residue; starch decreased from 20% of the insoluble residue after exposure to "CO2 to 3 % after 5 hr in both attached and detached leaves. The transition from import to export of attached and detached leaves was at the same stage, i.e., when the cotyledons were 63 to 85% depleted. The composition of the "C-assimilates in importing leaves was different from that in exporting leaves. In the former, only 5% of the soluble label was free sugar, while 74% was free sugar in the latter. The failure of importing leaves to export was not due to the labeled substances being nontransferable. Extracts from importing leaves applied to exporting leaves were exported; these extracts were high in amino acids and organic acids but low in free sugar. However, exporting leaves exposed to "CO2 appeared to export sugars more readily than amino acids. Cotyledon excision did not delay transition of leaves from import to export. Actually, excision seemed to enhance slightly the transition of the primary leaves from import to export.The source-to-sink concept of movement of food materials in the phloem of higher plants is supported by numerous experiments (1,3,8). It has been shown that a leaf during its ontogeny functions first as a metabolic sink and later, before it has expanded to its final size, as a metabolic source (3,12,17 by factors in other parts of the plant? How is this shift related to intensity of photosynthesis and composition of the metabolites? We attempted to obtain some answers to these questions by conducting studies on the primary leaves of bean (Phaseolus vulgaris L.) in different phases of expansion. Comparisons were made on the transport and metabolism of "C-assimilates in attached and detached leaves. Hartt and Kortschak (10), working with sugarcane, came to the conclusion that results from detached leaves were applicable to translocation in the entire plant. Leonard and Glenn (14,15) concluded from their work with excised bean leaves that these could be used in certain studies on the translocation of both assimilates and leafapplied substances. Also, results from our current work indicate that detached leaves can aid with studies on transport in leaves, especially on the transition from import to export.

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Translocation of 14Carbon in Tobacco following Assimilation of 14Carbon Dioxide by a Single Leaf

Cited by 99 publications

References 0 publications

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

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

Translocation Into Mature Leaves–the Effect of Growth Pattern

Translocation and Metabolic Conversion of ¹⁴C-Labeled Assimilates in Detached and Attached Leaves of Phaseolus vulgaris L. in Different Phases of Leaf Expansion

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Translocation of 14Carbon in Tobacco following Assimilation of 14Carbon Dioxide by a Single Leaf

Cited by 99 publications

References 0 publications

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

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

Translocation Into Mature Leaves–the Effect of Growth Pattern

Translocation and Metabolic Conversion of 14C-Labeled Assimilates in Detached and Attached Leaves of Phaseolus vulgaris L. in Different Phases of Leaf Expansion

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Product

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Translocation and Metabolic Conversion of ¹⁴C-Labeled Assimilates in Detached and Attached Leaves of Phaseolus vulgaris L. in Different Phases of Leaf Expansion