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https://hdl.handle.net/2142/71787
Description
Title
Photodynamic Herbicide Modulators
Author(s)
Montazer-Zouhoor, Ahmad
Issue Date
1988
Doctoral Committee Chair(s)
Rebeiz, Constantin A.
Department of Study
Horticulture
Discipline
Horticulture
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Chemistry, Agricultural
Biology, Plant Physiology
Abstract
Fourteen chemicals some of which having known chlorophyll biosynthetic modulating activities were tested for photodynamic herbicidal properties on the two major greening group of plants, i.e. the DDV/LDV and DMV/LDV groups. The following conclusions were made: (1) Cucumber, a DDV/LDV plant species, was highly susceptible to photodynamic herbicides. Protochlorophyllide was the most ubiquitous of the damage-causing anabolic photodynamic tetrapyrroles that accumulated as a result of treatments that consisted of ALA and one chlorophyll biosynthesis modulator. Furthermore, DDV/LDV plant species were more susceptible to ALA-based dark treatments that lead to MV Pchlide accumulation, than to those that led to DV Pchlide dark-accumulation. (2) Corn, a DMV/LDV plant species, and a representative of monocot crops, was not susceptible to the ALA-based photodynamic herbicides. Corn plants normally accumulate considerable amounts of tetrapyrroles at night, and can metabolize the accumulated tetrapyrroles when exposed to daylight. Corn plants treated with ALA and chlorophyll biosynthesis modulators, did not accumulate the "wrong" type of tetrapyrrole species (MV or DV) that were likely to force the generation of free radicals as was observed in cucumber plants. (3) The primary leaves of soybean, a DMV/LDV plant species, treated with ALA + chlorophyll biosynthesis modulators died after few days of exposure to daylight. The intact stems and cotyledons were not however affected and sustained the production of new leaves. The treated soybean plants soon recovered and continued to grow vigorously. (4) In some plant species phoeophorbide a, a catabolic tetrapyrrole played an important role in the photodynamic action of photodynamic herbicides. (5) ALA-based treatments caused ultrastructural changes in cucumber and soybean mesophyll cells. These changes consisted of: tonoplast rupture and separation of the plasma membrane from the cell wall, this in turn led to increased membrane permeability and severe plasmolysis, rupture of chloroplast membranes and ultimately chloroplast breakdown. The massive accumulation of osmiophyllic globuli in the treated mesophyll cells, probably were one expression of the accumulation of insoluble lipids derived from the disintegration of thylakoids. The continued and rapid breakdown of cellular components could therefore, be partly due to the release of vacuolar hydrolytic enzymes which occurred after the rupture of the tonoplast. The rupture of the tonoplast was a significant event at an early stage of the photodynamic herbicide treatments that led to irreversible cellular damage.
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