Functional strategies and life histories of grasses underlying yield and resilience

The family of Poaceae (grasses) includes many economically important crops. While grass grain crops (cereals) are typically annual, bioenergy and forage crops can have annual or perennial life histories. Annuals and perennials differ in important life history traits, such as the regulation of flowering and senescence, which determine to what extent resources are allocated to the grain, vegetative growth, or storage. These differences are also reflected in physiological characteristics; in particular, leaf traits that can be used to determine functional strategies (competitive, stress tolerant, or ruderal). While ruderality is associated with yield in annual grain crops, stress tolerance is usually higher in perennials. In this article, we discuss variation in functional strategies within perennial ryegrass grass (Lolium perenne) and species of the genus Brachypodium, demonstrating variation in characteristics for ruderality and stress tolerance. We argue that regulation of senescence of organs and whole plants determines these strategies and propose ideas on how functional strategies could potentially be optimised to increase grain yield in perennial grasses while maintaining stress resilience and other beneficial traits associated with perenniality.