High yielding perennial grasses, legumes, and grass/cereal hybrids are currently being investigated as potential alternative crops which could produce high yields of food or forage while also maintaining high levels of ecosystem services (lowered erosion, increased carbon sequestration, improved soil quality, and higher levels of pollinators and natural enemies as compared to annual systems). However, it is still unknown to what extent it will be possible to select perennial grasses and perennial grass/cereal hybrids for increased yield without jeopardizing the perennial life cycle. The answer to this question will depend on quantifying the cost of reproduction (i.e. how much reproduction one year reduces future growth and reproduction) and on determining whether photosynthesis can be upregulated to meet increased reproductive sink demand. Our study will examine the cost of reproduction in three perennial grains (intermediate wheatgrass, perennial wheat and perennial rye) and manipulate the carbon source/sink balance in order to examine underlying physiological processes that could underlie the ability to compensate for increased sink size. We will study two perennial wheat cultivars, an annual wheat control, perennial rye and intermediate wheatgrass over the course of three years, and carry out the following manipulations of the source/sink balance:
- Carbon enrichment (source augmentation)
- Clipping flowering heads (sink reduction)
- Shading of individual tillers (source reduction)
We will measure photosynthetic response curves and carbohydrate storage in order to better understand the carbon balance of the plants and their ability to compensate for changes in source/sink balance, and we will track correlations between yields in one year and yields in succeeding years in order to determine the cost of reproduction in these plants. Our underlying questions will be the following:
- What is the cost of reproduction in perennial grain plants?
- To what extent can perennial grain plants compensate for changes in source/sink balance?
By answering these questions we will contribute to the growing body of knowledge about a potentially important new type of agricultural plant with short-lived perennial life histories.