Establishment, Optimization, and Characterization of Photoautotrophic Soybean Suspension Cultures
Horn, Michael Eugene
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https://hdl.handle.net/2142/77658
Description
Title
Establishment, Optimization, and Characterization of Photoautotrophic Soybean Suspension Cultures
Author(s)
Horn, Michael Eugene
Issue Date
1984
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)
Agriculture, Plant Culture
Language
eng
Abstract
A novel system was designed which allowed the photoautotrophic growth of a previously established chlorophyllous soybean cell line. The parameters of growth (fresh weight, dry weight, chlorophyll content, medium pH, dark O(,2) uptake, dark CO(,2) fixation, and light-driven CO(,2) fixation) were ascertained throughout the entire subculture period (14 days). Of particular interest was the almost nonexistent lag phase in the growth cycle and the rapid drops in medium pH and dark CO(,2) uptake (respiration). Light-driven CO(,2) fixation rates easily accounted for the increase in dry weight exhibited by the culture. Photoautotrophic growth was completely inhibited by 0.5 micromolar DCMU, a photosynthetic herbicide, while cells grown in the dark on 3% sucrose were inhibited less than 10% by the DCMU. The cells would not grow in the dark under photoautotrophic conditions (5% CO(,2), no sucrose). A comprehensive examination was made of all medium components in an effort to determine if any were limiting or supraoptimal for cell growth. Indole-3-acetic acid was found to be a superior auxin with five to ten milligrams per liter being the most effective. No other single component was found to significantly increase growth when varied in concentration. Photoautotrophic soybean cells were shown to have typical nitrate reductase activity peaks six days after subculture but did not evolve significant amounts of nitrogenous gas, a trait associated with the constitutive nitrate reductase activity found in young soybean leaves and cotyledons. The cells accumulated as well as excreted large quantities of asparagine, serine, and glutamine suggesting that nitrogen is stored in this manner. Under high CO(,2) levels, photoautotrophic soybean cells fixed most of the CO(,2) into the organic acids malate and citrate with most of the remaining fixed CO(,2) found in aspartate and glutamate. Under low CO(,2) levels, CO(,2) was fixed initially into 3-phosphoglyceric acid and hexose monophosphates. These quickly declined as a percentage while serine, glycine, aspartate and other amino acids gradually became the dominant fixation products.
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