3. Root system architecture in cereals
In cereals, the root system consists of a primary and several seminal
roots formed during embryogenesis and post-embryonic lateral and crown
roots, representing the root system (Fig 1A). Primary and seminal roots
emerge during germination to ensure water and nutrient uptake by the
emerging seedling. Short after germination, post-embryonic roots are
formed, elaborating sequentially the root system required to exploit
limited soil resources and respond to changing environmental conditions.
In cereals, primary and seminal roots are either ephemeral and
short-lived like in rice or remain functional over the whole life cycle
like barley, maize or wheat. The post-embryonic root system is composed
of the lateral and crown roots. Crown roots are shoot-borne roots
arising from the lower stem nodes of the main shoot and tillers. They
are established throughout the development of the plant, resulting
finally in the buildup of the majority of the mature root system.
Lateral roots are root-borne roots developing from primary, seminal and
crown roots; they confer several branching orders of the RSA.
Altogether, they contribute to a fibrous root system, typical of the
monocots. Up to now, cereals root systems have been studied in different
species of cereals, including rice (Oryza sativa ), maize
(Zea mays L.), or Pearl millet (Pennisetum glaucum (L.) R.
Br.).
Plants can sense the environment and nutrients and readjust their root
developmental program to optimize soil’s foraging. This ability to
modulate root growth angle toward a specific resource or environmental
stimulus shape the RSA. Studying the molecular regulation of the RSA,
which is a crucial determinant for plant anchorage, water and nutrient
uptake efficiency, and the establishment of plant microorganisms’
communities, promises to improve crop yield.