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

Lazof, Dennis Boyd

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Description

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

Issue Date

1987

Doctoral Committee Chair(s)

Cheeseman, John M.

Department of Study

Plant Biology

Discipline

Botany

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Biology, Plant Physiology

Language

eng

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.

Graduation Semester

1987

Type of Resource

text

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