High floral bud abscission and lack of open flower abscission in Dendrobium cv. Miss Teen: rapid reduction of ethylene sensitivity in the abscission zone

Abstract

We studied the abscission of floral buds and open flowers in cut Dendrobium inflorescences. Abscission of floral buds was high and sensitive to ethylene in all cultivars studied. Many open flowers abscised in most cultivars, but cv. Willie exhibited only small amount of floral fall and cv. Miss Teen none. Applied ethylene (0.4 μL L–1 for 24 h at 27°C) greatly hastened abscission of open flowers in most cultivars, but had only a small effect in cv. Willie and no effect in cv. Miss Teen. Flower fall, if it occurred, was completely inhibited by 1-methylcyclopropene (1-MCP), showing that it was regulated by endogenous ethylene. Ethylene production from the abscission zones was low in all cultivars studied. In cv. Miss Teen the abscission zone changed from highly ethylene sensitive to completely insensitive in ~30 h, coinciding with floral opening. Removal of the floral buds somewhat reduced abscission in open flowers, but the lack of open flower abscission in cv. Miss Teen could not be explained by higher bud fall. The ovary did not grow in the (unpollinated) flowers, showing that lack of abscission in cvv. Willie and Miss Teen was not due to parthenocarpy. Flower removal in cv. Miss Teen had no effect on ethylene sensitivity of the abscission of the remaining pedicel. However, removal of the distal 2 cm of the 3-cm-long pedicels dramatically increased ethylene sensitivity. This suggests that the pedicel is important for the low ethylene insensitivity of abscission, in this cultivar. It is concluded that the abscission zones in the cvv. Willie and Miss Teen, in contrast with the other cultivars investigated, became rapidly insensitive to ethylene at the time of flower opening. At least part of the ethylene sensitivity in Miss Teen seems to be due to a factor in the pedicel.

The anti-ethylene growth regulator silver thiosulfate (STS) increases flower production and longevity in cassava (Manihot esculenta Crantz)

“…Previous studies of ethylene effects on flower development have focused on flower senescence and abscission. In flowers, ethylene hastens mature flower senescence and anti-ethylene treatments such as STS and 1-MCP extend the time from flower opening until senescence (Bunya-Atichart et al 2006;Dar and Tahir 2018;Rice et al 2013). Consistent with this, in the present study, when cassava plants that had set flowers were treated with exogenous ethephon to generate ethylene, senescence and abscission of flowers was stimulated, whereas pre-treatment with the anti-ethylene agent STS protected flowers from ethylene-induced senescence and abscission (Fig.…”

The Dendrobium Orchid: Botany, horticulture, and utilization

“…Open florets seemed to be more sensitive to ethylene than floral buds (Imsabai & Laongkaew, 2017). Pretreatment with ethylene inhibitors 1‐MCP, AOA, and STS prevented premature senescence induced by ethylene treatment (Bunya‐atichart et al., 2006; Kirasak, 2010; Lerslerwong & Ketsa, 2008; Lerslerwong et al., 2009; Uthaichay et al., 2007).…”

“…Flower removal in “Miss Teen” had no effect on ethylene sensitivity of the abscission of the remaining flowers and buds on the pedicel. However, removal of the distal 2 cm of the 3‐cm‐long pedicels dramatically increased ethylene sensitivity of “Miss Teen.” This suggests that the pedicel is important for the ethylene insensitivity of abscission in “Miss Teen.” It was concluded that the abscission zone (AZ) in “Miss Teen” became rapidly insensitive to ethylene at the time of flower opening (Bunya‐atichart et al., 2006). Ethylene is reported to trigger ethylene responses by first binding to the endoplasmic reticulum‐localized receptors, including ethylene response 1 ( ETR1 ), ethylene response sensor 1 ( ERS1 ), ETR2 , ERS2 , and ethylene insensitive 4 ( EIN4 ) to inhibit these receptors from interacting with and activating the negative ethylene signaling regulator constitutive triple response 1 ( CTR1 ) (Binder, 2020; Guo & Ecker, 2004; Liu & Chen, 2021).…”

“…The response to ethylene varies widely among Dendrobium cultivars (Almasi et al, 2012;Bunya-atichart et al, 2006;Imsabai & Laongkaew, 2017;Kirasak, 2010;Sirikesorn et al, 2015;Uthaichay et al, 2007). Individual Dendrobium flowers that have been exposed to ethylene exhibit many symptoms of premature senescence including epinasty, floret drooping, venation and water soaking of petals, and flower drop.…”

“…Individual Dendrobium flowers that have been exposed to ethylene exhibit many symptoms of premature senescence including epinasty, floret drooping, venation and water soaking of petals, and flower drop. The rapidity of symptom expression depends on the exposure duration and on the concentration of ethylene (Almasi et al, 2012;Bunya-atichart et al, 2006Bunya-atichart et al, , 2011Ketsa & Rugkong, 2000a;Lerslerwong & Ketsa, 2008;Sirikesorn et al, 2015). Ethylene treatment mimics the effects of pollination on floral lifespan (van Wouter, 2002).…”