Maize mesocotyl: Role in response to stress and deep‐sowing tolerance

Abstract

Maize (Zea mays L.) is one of the most important crops worldwide and is a model organism among cereal crops. Abiotic and biotic stresses are often present simultaneously and severely influence maize production, causing great yield losses worldwide. Therefore, the selection and cultivation of stress‐tolerant maize lines that adapt to various stresses is instrumental in addressing the problem of yield losses caused by stress. The maize mesocotyl is the crucial organ that pushes shoots out of deep water or soil after seed germination. It has a simple anatomy and exhibits rapid growth in the dark. In this article, we reviewed the studies on the elongation of the maize mesocotyl and the actions of phytohormones, especially under deep‐sowing conditions, and emphasized the role of the maize mesocotyl in response to environmental stress and deep‐sowing tolerance. We propose that the maize mesocotyl can serve as a selection organ for evaluating stress tolerance at the early seedling stage. We also identify future research fields that need further investigation in studies of the maize mesocotyl.

Genetic variation of seedling traits responded to brassinosteroid and gibberellin inhibitors in maize (Zea mays) doubled haploid lines

“…Deep sowing is an effective measure to ensure that seeds absorb water from the deep soil layer and emerge normally in arid and semi‐arid regions. It also prevents damage from the surface application of harmful chemicals (Niu, Hao, Wu, & Wang, 2020). Mesocotyl elongation acts as the single crucial response to make germplasm tolerant to deep sowing (Troyer, 1997; Zhao et al., 2010).…”

“…Modern maize varieties have been selected for productivity at high planting density and for reduced shade‐avoidance response (Fellner, Ford, & Van Volkenburgh, 2006; Niu et al., 2020). When crops grow under shade conditions, responses include increased growth of the hypocotyl and stem, as well as leaf hyponasty and petiole extension, and involve the action of multiple hormones, including auxin, ethylene, brassinosteriods and GAs (Colebrook et al., 2014).…”

Primary Root and Mesocotyl Elongation in Maize Seedlings: Two Organs with Antagonistic Growth below the Soil Surface

“…The embryo proper contains the root meristem (RAM) and the shoot meristem (SAM), relevant during the vegetative and reproductive phases for the development of the plant; these consist of a pool of stem cells that divide to give rise to more daughter cells that undergo cell division and differentiation throughout the entire life of the plant ( Figure 2 ). The roots and mesocotyl continue to grow using a combination of cell division in the meristems and cell elongation in subapical regions named elongation zones, which are highly controlled by several mechanisms [ 16 , 58 , 59 , 60 , 61 ].…”

“…Maize germination occurs in the dark when the seed contains at least 30% ( v / w ) moisture [ 61 , 74 ]. Initially, the primary root (PR) is formed at the basal pole from the embryonic radicle, and a variable number of seminal roots (SR) are laid down at the scutellar node.…”

“…The morphology and the anatomy of the maize mesocotyl are described as having several zones. In transversal slides, observed from outside to inside, these are the epidermis, cortex, and central vascular stele; in longitudinal slides, the first zone observed is next to the coleoptilar node (approximately 1.0 mm), including meristematic cells, the second zone (3.0 mm below) contains rapidly growing cells, and the third zone (5.0 mm below) near to the escutellar node presents mature cells ( Figure 3 ) [ 61 ]. The mesocotyl also uniquely responds to environmental cues and to stress conditions, whereby some maize lines develop fine roots capable of extensive growth [ 91 ].…”