(100-79) Different carbon allocation strategies in annual and perennial species of Brachypodium at reproductive stage under carbon limitation induced by drought
Body of Abstract: Annual and perennial plants have different life history and thus different carbon allocation strategies to growth and reproduction. This life history diversity provides genetic variation to study the mechanisms regulating carbon allocation across different tissue types. These allocation differences might be amplified under carbon perturbations, e.g., with carbon limitation. In this study, using drought as an abiotic stress to limit carbon acquisition, we use Brachypodium distachyon (annual) and B. sylvaticum (perennial) as models to study the different allocation strategy under carbon limitation at reproductive stage. With a similar drought stress, diagnosed as similar reductions net photosynthesis rate, annual and perennial plants have different allocation strategies. As we expected, the weight gain of seeds at grain filling stage during dry-down is not affect by drought stress compared to control in annual plants but decreased significantly in perennial plants. Seed respiration rate is also decreased in perennial plants compared to control, suggesting decreased metabolic activity in seeds in perennial plants. Accordingly, the root shoot ratio in perennials shows increase but not in annuals, suggesting that photosynthate that was destined for seeds instead is allocated to vegetative growth. Time-staged tissue-specific gene expression and metabolic samples will further allow us to explore possible molecular mechanisms driving these developmental differences between species. Our work represents a critical step in understanding the cause and consequence of resource partitioning in response various carbon perturbations, including increasing atmospheric CO2 and bioengineered enhanced carbon acquisition.