Date of Award

2024

Document Type

Thesis

Degree Name

Bachelors

Department

Natural Sciences

First Advisor

Clore, Amy

Area of Concentration

Biology with Chemistry

Abstract

Hypothesized to have originated from rhizosphere bacteria, bacterial endophytes dwell in the tissues of every plant tested and provide many benefits to their host, which can range from abiotic/biotic stress tolerance to disease resistance, all because of their influence on plant metabolism, gene expression, and morphology. Totipotency plays an important role in the differentiation of cells into a variety of cell types, in this study pertaining to Brassica oleracea var botrytis (common cauliflower) head explants (or excised fragments), as they develop in culture in the presence of three bacteria: Ralstonia insidiosa, Bacillus cereus, and Staphylococcus epidermidis. Although the metabolites synthesized by endophytes are studied extensively for their value, largely in the healthcare industry, the effects of exogenously applied endophytes on plant growth are studied less frequently. This thesis aimed to focus on the latter aspect of endophytes. The bacteria were tested for influences on the growth and development of cauliflower head (curd) explants, each for six weeks with weekly measurements recorded, totaling four trials. Due to contamination of some plates and their removal reducing the sample size, the results remain largely inconclusive on whether these particular species aid in the development of cauliflower organs. However, the following observations were made. 1) Dipping cauliflower into B. cereus has deleterious effects. 2) Nutrient broth-treated control explants grow exceptionally well and understandably so. 3) R. insidiosa seems to promote more root growth; its inoculated explants exhibited a relatively greater number of roots with numerous root hairs and clusters of roots at the site of emergence. Finally, 4) R. insidiosa conditioned medium supernatant had limited influence in stimulating organogenesis in comparison to the bacterial inoculation itself, suggesting that the presence of the bacteria may be required for altered growth rather than just its soluble metabolites alone. Discussion on alternative ways to eliminate contaminants and further tests that can be done to more definitively elucidate the effects of endophytes are also provided.

Download

Share

COinS