Ethephon Substrate Drenches Inhibit Stem Extension of Floriculture Crops

Abstract

<jats:p>Ethephon [(2-chloroethyl) phosphonic acid] is a plant growth regulator that releases ethylene on application and can abort flowers, stimulate branching, and inhibit stem elongation. Although ethephon is used as a foliar spray during the commercial production of many ornamental crops, its effectiveness as a drench has not been widely investigated. We performed experiments to quantify the effects of an ethephon drench on growth and flowering of a range of bedding plant and <jats:italic>Narcissus</jats:italic> cultivars and to assess the effect of lime on ethylene release from a peat substrate. A substrate drench of 0, 100, 250, or 500 mg·L<jats:sup>−1</jats:sup> ethephon was applied to 12 potted <jats:italic>Narcissus</jats:italic> cultivars at one location, and up to 200 mg·L<jats:sup>−1</jats:sup> was applied to 24 cultivars of bedding plants at three locations. Compared with untreated controls, ethephon generally reduced plant height at flowering and the effect increased with increased concentration. For example, <jats:italic>Narcissus</jats:italic> treated with a 250 mg·L<jats:sup>−1</jats:sup> ethephon drench had stems that were 20% to 40% shorter at the end of flowering than control plants. However, ethephon drenches generally caused a 2- to 3-day flowering delay, and two cultivars had a phytotoxic response. Among the bedding plants studied, a 100-mg·L<jats:sup>−1</jats:sup> ethephon drench suppressed plant height at flowering by greater than 30% in <jats:italic>Catharanthus</jats:italic>, <jats:italic>Celosia</jats:italic>, <jats:italic>Dianthus</jats:italic>, and <jats:italic>Verbena</jats:italic>, but by only 10% to 15% in <jats:italic>Lobelia</jats:italic>, <jats:italic>Lycopersicon</jats:italic>, and <jats:italic>Tagetes</jats:italic>. The drenches also delayed flowering in 10 of the 16 crops measured and decreased dry mass accumulation in all of the crops measured. Ethephon release from peat substrate became maximal ≈120 h after application and was dramatically increased by incorporation of dolomitic lime up to a rate of 9.5 kg lime per m<jats:sup>3</jats:sup> of peat. Collectively, these studies show that ethephon substrate drenches inhibit stem elongation in a broad range of floriculture crops, but can also delay flowering and reduce biomass accumulation.</jats:p>

Concentration and Timing of Ethephon Drench Applications Interact to Affect Growth and Flowering of Containerized Angelonia and Geranium

“…Our results agree with previous reports on the effects of ethephon drenches on annuals (Aiken et al, 2015;Miller et al, 2012). Miller et al (2012) reported time to flower for numerous annuals treated with ethephon at different institutions.…”

“…Our results agree with previous reports on the effects of ethephon drenches on annuals (Aiken et al, 2015;Miller et al, 2012). Miller et al (2012) reported time to flower for numerous annuals treated with ethephon at different institutions. Plants were treated 2 d after transplanting at Cornell University and, while flowering for snapdragon (Antirrhinum majus) and dianthus (Dianthus chinensis) were unaffected by ethephon, flowering of eight other species was delayed by 1.8-30.7 d. When plants at Michigan State University were treated 10 d after transplanting, tomato (Lycopersicon esculentum) and petunia flowering was delayed, whereas snapdragon, bedding impatiens (Impatiens walleriana), and osteospermum (Osteospermum fruticosum) flowering was not.…”

“…Spray applications are easy to apply and can provide adequate growth control, though substrate drenches can increase growth control uniformity and duration (Currey et al, 2010;Currey and Lopez, 2011;Currey et al, 2012). Ethephon is not currently labeled for application via substrate drenches, though recent research reports the promise of using drenches for growth control (Aiken et al, 2015;Miller et al, 2012). Miller et al (2012) noted that ethephon drench activity appeared to vary when plants were treated early (2 d after transplanting) as opposed to later (10 d after transplanting); however, application times were not a controlled factor and varied across locations.…”

“…Ethephon is not currently labeled for application via substrate drenches, though recent research reports the promise of using drenches for growth control (Aiken et al, 2015;Miller et al, 2012). Miller et al (2012) noted that ethephon drench activity appeared to vary when plants were treated early (2 d after transplanting) as opposed to later (10 d after transplanting); however, application times were not a controlled factor and varied across locations. Since PGR application timing is important to elicit desirable and appropriate plant responses, it is important to quantify the effect of application timing to determine best management practices for using ethephon drenches (Bailey and Whipker, 1998).…”

Ethephon Foliar Sprays Are Influenced by Carrier Water Alkalinity and Ambient Air Temperature at Application

“…Ethephon breaks down to release the plant hormone ethylene (C 2 H 4 ) as well as chlorine (Cl -), and hydrogen phosphate (H 2 PO 4 -) (Biddle et al, 1976). It is labeled for foliar spray applications on floriculture crops to increase lateral branching, abort flowers and flower buds, and inhibit internode elongation (Currey et al, 2016b;Hayashi et al, 2001); although not labeled, recent research has shown that it can be effective as a substrate drench (Currey et al, 2016b;Miller et al, 2012). The increase in lateral branching is due to an inhibition of apical dominance (Andersen, 1976), and the control of flowering is due to ethylene-induced flower and flower bud abscission (Roberts et al, 1984).…”