Invasive plants establish, develop and reproduce under a wide range of maternal environmental conditions that not only affect reproductive allocation, but also traits associated with seed persistence in the soil, such as dormancy and maintenance of vigor. Phenolic compounds may be linked to these seed persistence mechanisms by deterring herbivory and decay, acting as antioxidants to slow aging, and inhibiting germination. Allocation of phenolic compounds to seeds may therefore play an important role in determining the invasion potential of many weedy species, allowing these species to disperse their seeds over time. Climate change may also affect reproductive allocation and seed quality, with great implications for the establishment and proliferation of invasive plants. Since elevated carbon dioxide tends to improve water use efficiency, reduce competition for Rubisco fixation, and suppress photorespiration, stress-induced reductions in seed quality may be mitigated by elevated carbon dioxide, permitting invasive plants to expand into new habitats or become more competitive in their current ranges.

Results/Conclusions

Preliminary experiments on wild oat (Avena fatua) indicate that drought stress during seed maturation negatively impacts reproductive allocation and seed persistence. Stressed plants produce fewer, smaller, and less dormant seeds than non-stressed plants. For example, after 18 weeks of after-ripening, an average of 84.67% of the seeds from drought-stressed plants germinated, compared to only 53.67% of seeds from control plants. Drought stress also appears to impact the allocation of phenolic compounds to seeds.  Seeds from drought-stressed plants of the isoline M73 have an average concentration of 80961.91 pg/seed, while seeds from well-watered plants have an average concentration of 101411.9 pg/seed. In addition, the concentrations of vanillic, coumaric and ferulic acids in seeds from drought-stressed plants decrease by 28.53%, 19.38%, and 22.41%, respectively. The current experiment tests the hypothesis that elevated carbon dioxide will mitigate the effects of stress on fecundity and seed quality. Trends show that plants in the elevated (760ppm) carbon dioxide treatment are larger, have greater photosynthetic rates, and are less affected by drought stress than plants in the ambient (366ppm) environment. Additional data on seed quality will be presented.