DISCUSSION
Several studies have explored plant responses to P-stress at different levels, from biochemical and molecular, through physiological to developmental. However, few of the past studies have taken broad, integrative approaches encompassing all these levels, and most if not all of these have focused on annual plant species, especially model species (Morcuende et al., 2007; Hernandez et al., 2007). Here, we have focused on long-term effects of P-stress in the important perennial grass, P. virgatum , or switchgrass, integrating experiments on plant growth and development with genome-wide analysis of transcriptional responses and metabolism. While many of the adaptive responses of switchgrass to P-stress are conserved in annual plant species that have been studied, some unusual responses were found in switchgrass, such as storage of significant Pi in shoots of severely P-stressed plants, which may reflect the perennial nature of this species. Below, we compare and contrast P-stress responses of switchgrass with those of other plant species.