Hormonal Effects on Growth and Morphology of Normal and Hairy Roots of Hyoscyamus muticus

Abstract

Treatment of normal and Agrobacterium rhizogenes-transformed root cultures of Hyoscyamus muticus with three different auxins, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), and naphthaleneacetic acid (NAA), revealed that the response varied considerably among auxins, between transformed and normal roots, and depending on the parameter. In normal roots all three auxins provoked abundant branching, with IBA and NAA being the most effective at 2.5 and 0.5 M, respectively, whereas IAA was most effective at low concentrations (0.05 and 0.1 M). In transformed roots exogenously supplied auxins were generally inhibitory or, at best, without effect on growth and branching. Only 0.01 M IAA significantly enhanced lateral root number, whereas at the higher concentrations IBA, although inhibitory, was the least effective auxin. In both root types IBA had little effect on primary root growth, but normal roots were more sensitive to IAA and NAA. These results suggest a different sensitivity to auxins of normal and transformed roots since there was no significant difference in endogenous free and conjugated IAA content nor in IAA uptake capacity. Ethylene production and biosynthesis were approximately threefold higher in hairy roots, but production could be stimulated up to tenfold that of control levels in normal roots by supplying NAA or 1-aminocyclopropane-1-carboxylic acid (ACC). Treatment with 2.5 M NAA, but not IAA or IBA, also enhanced ethylene biosynthesis in normal roots but not in transformed ones. ACC and malonyl-1-aminocyclopropane-1-carboxylic acid accumulated to detectable levels only after treatment with an auxin (NAA).

Effect of auxins on Karwinskia humboldtiana root cultures

“…Various growth regulators influence in different way the root induction, elongation, and biomass production (Gyulai et al, 1993;Biondi et al, 1997;Vanhala et al, 1998;Ba´lva´nyos et al, 2001;Balestri and Bertini, 2003).…”

“…However, they can be used also as model systems in the research focused on the effect of various substances on roots, e.g. growth hormones (Biondi et al, 1997;Taylor and van Staden, 1998;Vanhala et al, 1998;Ba´lva´nyos et al, 2001), oligosaccharides (Lozovaya et al, 1993;Zabotina et al, 1997;De Ruijter et al, 1998), heavy metals (Guadagnini et al, 1999), etc. Most of these studies were focused on root induction, elongation, and on root/root cultures biomass production.…”

Using an aerosol deposition model to increase hairy root growth in a mist reactor

“…Hairy roots produce ethylene, in some instances in greater quantities than untransformed roots (Biondi et al, 1997), and the growth of A. annua roots is significantly decreased in the presence of ethylene (Weathers et al, 2005). When the vent gas from the small reactor was tested for ethylene using the triple response of pea seedlings (Neljubow, 1901), none was found.…”

Identification of genetic factors controlling the efficiency of Agrobacterium rhizogenes-mediated transformation in Brassica oleracea by QTL analysis

“…It is widely documented that the combined introduction of both the TL-and TR-DNA induces adventitious root production (Vilaine and Cassedelbart 1987;Capone et al 1989;Zhan et al 1990;Biondi et al 1997). The induction of phenotypically normal non-transgenic adventitious root production upon A. rhizogenes infection has been previously reported in woody species and Chrysanthemum (van Wordragen et al 1992;Yibrah et al 1996;Falasca et al 2000).…”