The effects of parental CO2 environment on seed quality and subsequent seedling performance in Bromus rubens

Seeds were collected and compared from parent plants of Bromus rubens L. (Poaceae), an exotic Mojave Desert annual grass, grown in ambient (360 mu mol mol(-1)) and elevated (700 mu mol mol(-1)) CO(2) to determine if parental CO(2) growth conditions affected seed quality. Performance of seeds developed on the above plants was evaluated to determine the influence of parental CO(2) growth conditions on germination, growth rate, and leaf production, Seeds of B. rubens developed oil parents grown in elevated CO(2) had a larger pericarp surface area, higher C:N ratio, and less total mass than ambient-developed seeds, Parental CO(2) environment did not have an effect on germination percentage or mean germination timer as determined by radicle emergence. Seedlings from elevated-CO(2)-developed seeds had a reduced relative growth rate and achieved smaller final mass over the same growth period. Elevated-CO(2)-developed seeds had smaller seed reset-yes than ambient seeds, as determined by growing seedlings in sterile media and monitoring senescence. It appears that increased seed C:N ratios associated with plants grown under elevated CO(2) may have a major effect on seed quality (morphology, nutrition) and seedling performance (e.g., growth rate and leaf production). Since the invasive success of B. rubens is primarily due to its ability to rapidly germinate, increase leaf area and maintain a relatively high growth rate compared to native annuals and perennial grasses, reductions in seed duality and seedling performance in elevated CO(2) may have significant impacts on future community composition in the Mojave Desert.