Etiolation and flooding of donor plants enhance the capability of Arabidopsis explants to root

Abstract

Rooting of cuttings depends not only on the rooting treatment and the genotype, but also on the condition of the cuttings at the time of excision. The physiological and developmental conditions of the donor plant may be decisive. We have examined in Arabidopsis the effect of two donor plant pre-treatments, etiolation and flooding, on the capability of flower stem and hypocotyl segments to root. For etiolation, plantlets were kept in the dark, hypocotyls up to 12 days and plantlets for 12 weeks. Flooding was applied as a layer of liquid medium on top of the semi-solid medium. This procedure is also referred to as “double layer”. Both pre-treatments strongly promoted rooting and we examined possible mechanisms. Expression of strigolactone biosynthesis and signaling related genes indicated that promotion by etiolation may be related to enhanced polar auxin transport. Increased rooting after flooding may have been brought about by accumulation of ethylene in the cutting (ethylene has been reported to increase sensitivity to auxin) and by massive formation of secondary phloem (the tissue close to which adventitious roots are induced). Both pre-treatments also strongly lowered the endogenous sucrose level. As low sucrose favors the juvenile state and juvenile tissues have a higher capability to root, the low sucrose levels may also play a role.