The transcription of this gene was shown to be induced in feeding sites of root-parasitic nematodes (Heterodera schachtii), in roots infected by a fungus-like organism (Plasmodiophora brassicae), by plant hormone treatment, and by wounding.
This stimulation is mediated by ethylene, which induces the expression of cell cycle regulatory genes in crown root meristems and promotes, in synergy with gibberellic acid, the death of epidermal cells at the site of root emergence (Lorbiecke and Sauter [1999]; Mergemann and Sauter [2000]; Steffens et al. [2006]).
Therefore, providing high concentrations of nutrients that stimulate root growth at the site of root contact (e.g. NH4 + and HPO4 2−/H2Por − or CO NH2 2 and HPO4 2−/H2PO4 −, the later under optimal ammonification conditions) [2, 5] and are poorly mobile in soil [6 9], crops can more efficiently acquire fertilizer-depot nutrients, thus improving their yields [4].
XET activity has been demonstrated to be localized to the site of root hair bulge formation [ 9], suggesting a specific role in hair formation.
In Arabidopsis, sterol accumulation also marked the site of root hair emergence, while polarised distribution of sterols on tip-localised SVs and apical PM was required for root hair elongation (Ovecka et al., 2010).
The root tip and sites of lateral root emergence were found to be hotspots for fast-growing cells.
In tomato where disease development has been well studied, bacteria attach to root surfaces and form micro-colonies, especially at the root elongation zone and sites of lateral root emergence.
Comparing the branching sites of the root canals within mesial and distal roots, division of the distal root canal was located further apically and in most cases was seen even apically of the enamel extension, with this being independently of tooth age.
HS were found to have marked effect on the emergence of lateral roots and the hyperinduction of sites of lateral root emergence upon HS treatments have been observed (Figure 2B; [16] 16]).
