Mechanisms of Floral Induction in Grasses: Something Borrowed, Something New

Almost all that is known about the transition to flowering in grasses is based on studies of agronomic species. The grain produced by two tropically derived grasses, maize (Zea mays) and rice (Oryza sativa), and a temperate origin grass, wheat (Triticum aestivum), provides most of the world's food. Other grasses, such as barley (Hordeum vulgare), ryegrass species (Lolium spp.), sorghum (Sorghum bicolor), and oats (Avena sativa), are grown in lesser amounts, but also fill important food production niches. In grass species, such as sugarcane (Saccharum spp.), the vegetative portion of the plant is harvested for the Suc that accumulates in its stalks; in this crop, the inability to flower is desirable because sugar levels drop after plants make the transition to flowering as carbon assimilates are shunted to seed production. In all of these grasses, manipulation of the timing of the floral transition is a vitally important trait in maximizing yield potential. Extensive agronomic studies have been done on grass species, but studies of the small flowering dicot plant Arabidopsis (Arabidopsis thaliana) have provided an abundance of information on the genetic and molecular control of flowering. What has emerged is a complex network of genes and pathways, some parts of which are also found in the grasses. Conversely, recent discoveries show that grasses also have developed unique mechanisms to regulate flowering.