Studies in Sieve-tube Exudation through Aphid Mouth-parts: The Effects of Light and Girdling1

Peel, A. J.; Weatherley, P. E.

doi:10.1093/oxfordjournals.aob.a083822

Cited by 49 publications

(22 citation statements)

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“…A turgor pressure gradient must be created in the opposite direction by an osmotic pressure gradient to counteract and exceed the water potential gradient created by transpiration and to overcome the viscous pressure losses due to phloem transport itself. For instance, experimental evidence shows decreased phloem exudation rate in connection with more negative xylem water potentials (Hall and Milburn, 1973;Peel and Weatherly, 1962).…”

Section: Accepted Manuscript 3 Linking Powered By Extmentioning

confidence: 99%

Linking phloem function to structure: Analysis with a coupled xylem–phloem transport model

Hölttä

Mencuccini

Nikinmaa

2009

Journal of Theoretical Biology

200

188

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Cite this article as: T. Hölttä, M. Mencuccini and E. Nikinmaa, Linking phloem function to structure: Analysis with a coupled xylem-phloem transport model, Journal of Theoretical Biology (2009Biology ( ), doi:10.1016Biology ( /j.jtbi.2009 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. We carried out a theoretical analysis of phloem transport based on Münch hypothesis by developing a coupled xylem-phloem transport model. Results showed that the maximum sugar transport rate of the phloem was limited by solution viscosity and that transport requirements were strongly affected by prevailing xylem water potential. The minimum number of xylem and phloem conduits required to sustain transpiration and assimilation, respectively, were calculated. At its maximum sugar transport rate, the phloem functioned with a high turgor pressure difference between the sugar sources and sinks but the turgor pressure difference was reduced if additional parallel conduits were added or solute relays were introduced. Solute relays were shown to decrease the number of parallel sieve tubes needed for phloem transport, leading to a more uniform turgor pressure and allowing faster information transmission within the phloem. Because xylem water potential affected both xylem and phloem transport, the conductance of the two systems was found to be coupled such that large structural investments in the xylem reduced the need for investment in the phloem and vice versa.

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Section: Accepted Manuscript 3 Linking Powered By Extmentioning

confidence: 99%

Linking phloem function to structure: Analysis with a coupled xylem–phloem transport model

Hölttä

Mencuccini

Nikinmaa

2009

Journal of Theoretical Biology

200

188

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“…The change of this profile in the ethanol-insoluble fraction with time suggests that the very rapid exchange between mobile material and storage cells shown for willow by Peel and Weatherley (1962) is also typical of soybean.…”

Section: (D) Profile Of Activity In Petiole and Stem Following Chillingmentioning

confidence: 91%

“…As the source leaf is the only expanded leafleft on these plants an alternate sucrose supply is necessary if continued movement of sugars down the stem is to occur after isolation of the source leaf. The suggestion of Peel and Weatherley (1962) that storage carbohydrates may be rapidly mobilized and moved to the phloem provides a possible means by which the sucrose content of the phloem might be maintained. Apparently a steep concentration gradient mediates the changeover to the alternate sucrose source.…”

Section: (F) Influence Of the Source Leaf On Translocation Following mentioning

confidence: 99%

Translocation of Labelled Assimilates in the Soybean IV. Some Effects of Low Temperature on Translocation

Thrower¹

1965

Aust. Jnl. Of Bio. Sci.

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SummaryTranslocation of 14C-Iabelled assimilate within the plant ceased when the plant was held at 2-3°C. Chilling a short length of petiole to 1°C prevented trans· location of labelled assimilate past the chilled section of petiole. When the petiole was again warmed, translocation through it was resumed. The time between warming the petiole and the resumption of translocation varied between 5 and 20 min.The profile of labelled material developed in the stem 30 min after chilling and rewarming was shown to be of logarithmic shape. This shape was lost after 2 hr. A logarithmic profile was obtained for both mobile and fixed labelled material. The rate of movement of the front of detectable activity down the stem was of the order of 17 cm/hr.Movement of labelled assimilate in the vascular tracts running downward from a particular leaf was inhibited when the leaf was isolated from the stem (by chilling), and enhanced when the root was deprived of assimilate from other leaves (by defoliation).

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“…Mortimer ( 13) found that the decline in "-C in a sugar beet petiole slowed after about 2 hr, at which time nearly 25 % of the peak activity remained, presumably stored along the path. Various workers have concluded that the stem and petiole may serve as sites for storage of translocate during peak assimilation periods, with remobilization of these reserves during periods of low productivity (8,10,14). Distribution of radioactivity among various categories of compounds is summarized in the data of table III.…”

Section: Methodsmentioning

confidence: 99%

“…Previous studies have shown that the path also serves as a sink for translocate (1,4,8,10,11,13,14). Several workers have suggested that accumulation along the translocation path helps maintain the solute concentration in the sieve tube sap during periods of fluctuating assimilation (10,14). The rate of lateral movement of translocate out of the sieve tubes is of interest in evaluating the extent of storage along the path, in formulating translocation models (4), and in interpreting translocation profiles (2).…”

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Translocation and Accumulation of Translocate in the Sugar Beet Petiole

1969

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Abstract. Accumulation of translocate during steady-state labeling of photosynthate was measured in the source leaf petioles of sugar beet (Beta vulgaris L. monogerm hybrid). During an 8-hr period, 2.7 % of the translocate or 0.38 #g carbon/min was accumulated per cm petiole. Material was stored mainly as sucrose and as oompounds insoluble in 800% ethanol. The minimum peak velocity of translocion approached an average of 54 cm/hr as the specific aotivity of the 34CO2 pulse was progressively increased. The ratio of cross sectional area required for translocation to actual sieve tube -area in the petiole was 1.2. A regression analysis of translocation rate versus sieve tube cross sectional area yielded a coefficient of 0.76. The specific mass transfer rate in the petiole was 1.4 g/hr cm2 phloem or 4.8 g/hr cm2 sieve tube. Histoautoradiographic studies indicated that translocttion occurs through the area of ph,loem occupied by sieve tubes and companion oells while storage occurs in these cells plus cambium and phloem parenchyma cells. The ability of the petiole to act as a sink for translocate is consistent with the conoept that storage along path tissue serves to buffer sucrose ooncentration in the translocate during periods of fluctuating assimilation.

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Studies in Sieve-tube Exudation through Aphid Mouth-parts: The Effects of Light and Girdling1

Cited by 49 publications

References 0 publications

Linking phloem function to structure: Analysis with a coupled xylem–phloem transport model

Linking phloem function to structure: Analysis with a coupled xylem–phloem transport model

Translocation of Labelled Assimilates in the Soybean IV. Some Effects of Low Temperature on Translocation

Translocation and Accumulation of Translocate in the Sugar Beet Petiole

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