Date of Award


Degree Name

Doctor of Philosophy


Environmental Science and Engineering


Joanne T. Ellzey

Second Advisor

Jorge L. Gardea-Torresdey


Phytoremediation is an emerging technology for cleaning industrial and urban contamination (Peuke and Rennenberg, 2005). Many factors including germination rate, biomass changes, biochemical changes, and nutrient changes must be determined in order to utilize a plant for phytoremediation. Our results showed that Prosopis pubescens (Screw bean mesquite) is a hyperaccumulator of copper from copper sulfate and a feasible option to remediate fields with up to 200 ppm of copper sulfate.

Screw bean mesquite seeds are viable even after 30 years of storage. Both copper sulfate and copper nitrate decreased the germination rate of screw bean mesquite seeds. In soil grown screw bean mesquite plants, germination rates were not affected by either copper sulfate or copper nitrate. Physiological studies showed biomass decreased with copper exposure. Root cell area increased with increasing copper exposure. Only after copper nitrate exposure, chlorophyll levels decreased; unmasking

the yellow/orange pigments from carotene and xanthophyll and causing chlorosis.

We measured copper and nutrient concentrations within seedlings. Petri dish grown seedlings accumulated 47,000 ppm (27,500 ppm) in roots, 23,000 ppm (21,000 ppm) in stems, and 9,000 ppm

(16,000 ppm of copper) in cotyledons from copper sulfate (copper nitrate). Control seedlings grown in soil accumulated 31,000 ppm in roots, 17,000 ppm in stems, 11,000 ppm in cotyledons, and 20 ppm of

copper from copper sulfate in true leaves. Copper did not change calcium, iron, manganese and zinc concentrations. Magnesium, potassium, phosphorus decreased while sulfur increased in Petri dish grown

seedlings exposed to copper sulfate and copper nitrate.

We identified various ultrastructural changes of cotyledons and true leaves due to copper toxicity including separation of the cell membranes from cell walls, denser cytoplasm with dark aggregates in epidermis, parenchyma, and developing phloem as well as increased vacuolization, swelling of chloroplasts and disarray of thylakoid membranes. Plasmolysis was evident beginning with 100 ppm of both copper sulfate and copper nitrate. Elemental analysis confirmed the presence of copper

in experimental samples.




Received from ProQuest

File Size

152 pages

File Format


Rights Holder

Marian Nicte Zappala