| Given the unprecedented increase in urbanization and its effect on natural ecosystems, the effort to restore human-impacted land is timely and essential. Flexible and stress-resistant plant genotypes may provide a practical solution for restoration of constantly changing and stressful environments, yet there has been little progress linking general stress tolerance with plants being used in urban restoration. This dissertation project uses a novel, experimental approach to test and determine the importance and effectiveness of phenotypically plastic and stress-resistant plant genotypes in the ecological restoration of urban and degraded land. Using a model system involving the annual cress, Arabidopsis thaliana and the heat-shock protein (HSP) induced stress response system; I began this dissertation by testing if the presence of an induced stress response (HSP17.6) was essential for overall success. I found that mutant plants lacking a working HSP17.6 response generally showed an inability to cope with various types of abiotic urban stress. This difference was generally more pronounced in high stress conditions, providing evidence of adaptive plasticity. I then expanded the investigation by using six field-collected Arabidopsis genotypes and by adding a molecular analysis of the expression of both HSP17.6 and HSP101. I tested for natural variation in stress response, and then sought to use that information to predict success in various stressful conditions. While I found natural variation both in phenotype and the expression of HSP genes in stress, I saw little correlation between HSP expression and fitness, suggesting that predicting plant success via such molecular data may have limited utility. I did, however, identify "stress-resistant" genotypes, which consistently performed best across all stress treatments. Finally, I tested whether those stress-resistant genotypes continued to exhibit success in novel stress conditions. They did, which suggests that simple preliminary stress tests can provide a reasonable and quick method of genotype selection, especially for practitioners restoring urban and degraded land. I conclude that stress-resistant genotypes may be the best option when planting in heterogeneous soils with unknown stressor combinations in novel urban restoration sites. |
