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Title:Compartmental Analysis of Roots in Intact Rapidly-Growing Spergularia Marina and Lactuca Sativa: Partial Characterization of the Symplasms Functional in the Radial Transport of Sodium Ion and Potassium Ion
Author(s):Lazof, Dennis Boyd
Doctoral Committee Chair(s):Cheeseman, John M.
Department / Program:Plant Biology
Discipline:Botany
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Biology, Plant Physiology
Abstract:Techniques of compartmental analysis were adapted to the study of intact roots of rapidly-growing Spergularia marine and Lactuca sativa. Using large numbers of plants short time-courses of uptake and chase, $\sp{42}$K$\sp+$ and $\sp{22}$Na$\sp+$ transport could be resolved, even during a chase following a brief 10 minute labeling period. The use of intact plant systems allowed distinction of that portion of the isotope flux into the root, associated with the ion-conducting symplasms.
A small compartment, which rapidly (t$\sb{.5}$ $<$ 1 min) exchanges with the external medium was implicated in the radial transport of N$\sp+$, accounting for the observed obtention of linear translocation rates within minutes of transferring to labeled solution. At the 90 mol m$\sp{-3}$ Na$\sp+$ steady-state, 90% of the contents of this compartment exchanged out to the medium during a chase, while the remaining 10% translocated to the shoot in the first few minutes of the chase. The ion contents of this compartment varied in proportion to the external ion concentration.
When K$\sp+$ was at a high external concentration, labeled K$\sp+$ exchanged into this same symplasm, but chasing a short pulse indicated that K$\sp+$ transport to the xylem was not through a rapidly-exchanging compartment. At physiological concentrations of K$\sp+$ the evidence indicated that transport of K$\sp+$ across the root proceeded through a compartment which was not exchanging rapidly with the external medium. The rise to a linear rate of isotope translocation was gradual and translocation during a chase, following a brief pulse, was prolonged, indicating that this compartment retained its specific activity for a considerable period.
In computer simulation modeling, it was shown that specialized ion-transporting symplasms needed to be incorporated into the compartmental model. An alternative model with specialized conducting compartments for Na$\sp+$ and K$\sp+$ was required to overcome the major difficulties. In the case of K$\sp+$, it was necessary to virtually eliminate uptake from the external medium by exchange in order to simulate the experimental results.
Issue Date:1987
Type:Text
Language:English
Description:160 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987.
URI:http://hdl.handle.net/2142/77666
Other Identifier(s):(UMI)AAI8803105
Date Available in IDEALS:2015-05-14
Date Deposited:1987


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