Comparisons of early root cortical senescence between barley cultivars, Triticum species and other cereals

Abstract

SUMMARYThe natural rate of root cortical death (RCD) in seminal roots was investigated in different cereals by staining the roots with acridine orange. In all cereals investigated the part of the cortex having stainable nuclei gradually decreased with increased age of the root. Wheat differed from barley, oats and rye in having a much faster rate of RCD. In 15-d-old root regions of wheat grown in soil, only 10-20% of the radius of the root had stainable nuclei. In barley, oats and rye the amount of cortex with stainable nuclei varied between 65 and 80 "o. Minor differences in RCD were found between different barley cultivars or accessions. Large variation in RCD was found between different Triticum species: T. monococcum, T. dicoccum and different Aegilops species had much slower RCD than did hexaploid wheat. These results are discussed in relation to microbial colonization of roots and susceptibility to root pathogens.

Functional implications of root cortical senescence for soil resource capture

“…In three-week-old root segments of wheat, the majority of root cortical cells were anucleate, although the roots still appeared white and healthy (Holden 1975;Holden 1976). Holden's findings were later confirmed (Deacon and Henry 1978;Henry and Deacon 1981;Kirk and Deacon 1986) and the phenomenon was termed 'non-pathogenic root cortex death' (Deacon and Henry 1978) and more recently referred to as RCS (Robinson 1990;Liljeroth 1995;Schneider et al 2017a). …”

“…RCS progresses fastest in the seminal roots of wheat followed by triticale, barley, rye, and oats respectively (Holden 1976;Deacon and Henry 1980;Henry and Deacon 1981;Deacon and Mitchell 1985;Yeates and Parker 1985;Kirk and Deacon 1986;Liljeroth 1995). In 15-day-old segments of wheat roots grown in soil, between 80 and 90% of the root cortical cells were anucleate, in contrast to between 20 and 35% anucleate cortical cells in barley and rye (Liljeroth 1995).…”

“…In 15-day-old segments of wheat roots grown in soil, between 80 and 90% of the root cortical cells were anucleate, in contrast to between 20 and 35% anucleate cortical cells in barley and rye (Liljeroth 1995). Several studies claim the identification of RCS in dicotyledonous species including in peanut (Arachis hypogaea) (Griffin et al 1975) and rape (Brassica napus L.) (MacLeod et al 1986).…”

“…In addition, lateral roots themselves do not form RCS (Henry and Deacon 1981;Schneider et al 2017b). RCS is complex and dependent on plant species, growth medium, and genetic and environmental cues (Liljeroth 1995;Schneider et al 2017a).…”

“…1) in Poaceae and forms in many species including triticale (Triticosecale) Liljeroth and Bryngelsson 2002), barley (Hordeum vulgare L.) (Deacon and Henry 1980;Liljeroth and Bryngelsson 2002), rye (Secale cereal) (Liljeroth 1995), oats (Avena sativa) (Liljeroth 1995), Kentucky bluegrass (Poa pratensis) (Smiley and Giblin 1986), perennial ryegrass (Lolium perenne) (Jupp and Newman 1987), blue grama grass (Bouteloua gracilis) (Beckel 1956), and wheat (Triticum aestivum) (Deacon and Henry 1980;Lascaris and Deacon 1991a;Liljeroth and Bryngelsson 2002). RCS was first observed by Henrici (1929) in South African xeric grasses and was first quantified by Holden (1975) using nuclear staining methods.…”