Biochemistry of Flower Senescence - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 60

yet been identified. The study of Sisler et al. (1993) reported on comparison of the effects
of STS and preirradiated DACP on preventing ethylene effects in cut carnation flowers
( Dianthus caryophyllus “White Sim”). The differences between treatments did not appear
during the 12 days of observation. Additionally, DACP delayed and reduced endogenous
ethylene production. In the study with sweet pea flowers, Sexton et al. (1995) investigated
the effect of DACP on bud drop from cut sweet pea flower spikes ( Lathyrus odoratus L).
DACP delayed both wilting and abscission of buds; however, it did not stop the processes as
effectively as it was reported for carnation petal senescence (Sisler et al., 1993). The ethylene
binding constants ( Kd values) in rose petals and leaves obtained indicates noncompetitive
inhibition by irradiated DACP, probably because DACP covalently attached to the binding
site when the diazo groups decomposed (Serek et al., 1994). This volatile compound has
been documented as a very strong ethylene action inhibitor; however, its instability and
explosive character makes it an unlikely candidate for commercial use.
4.4.2.4 1-Methylcyclopropene
The spectacular effect of 1-methylcyclopropene (1-MCP) has been well documented in a
range of ornamental species. The commercial producers of ornamental products in many
countries are already benefiting from this new development. 1-MCP is a cyclic olefin, which
seemingly irreversibly binds to ethylene receptors and prevents ethylene from inducing a
conformational change. The compound is nontoxic, odorless, stable at room temperature,
and has been shown to protect many cut flowers, potted plants, and other horticultural
commodities against ethylene. The physical and chemical properties, as well as synthesis
and mode of action of 1-MCP, have been reviewed by Sisler and Serek (2003). 1-MCP has
been patented in 1996 (Sisler and Blankenship, 1996) and is commercially produced by
AgroFresh Inc. ( SmartFresh ).
4.4.2.5 Other cyclopropenes
The effect of 1-MCP pretreatment generally has a limited duration. This most likely is due
to breakdown of receptor protein and the synthesis of new receptor molecules that are, due
to absence of the gas, not protected against ethylene (Sisler et al., 1996b). Further develop-
ment and testing of new compounds to achieve a broader working spectrum has therefore
been performed (Sisler et al., 2001). A number of 1-MCP-related compounds have been
investigated in order to find the most effective ethylene antagonists. Cyclopropene (CP)
and 3,3-dimethylcyclopropene (3,3-DMCP) have been tested in carnation and Campanula
(Sisler et al., 1996a); 3-methylcyclopropene (3-MCP) has been tested in Campanula and
Kalanchoe (Sisler et al., 1999). All these compounds were found to be efficient in protect-
ing plant tissue from the effect of ethylene, though the necessary concentrations varied.
None of these compounds performed better than 1-MCP. Contrary to these results, methy-
lene cyclopropane has been found to induce most of the same effects as ethylene does
(Sisler et al., 1996b). Apparently, this compound acts as an agonist instead of an antago-
nist. Later investigations showed that 1-substituted cyclopropenes (like 1-MCP) performed
better than any other compounds, and a range of such compounds substituted with various
carbon chains at the 1-position has been tested by Sisler et al. (2003). This has resulted
in a number of compounds with very desirable qualities. In this study, compounds with
all possible linear saturated side chains from methyl (CH 3 ) to decyl ((CH 2 )9CH 3 ) were
tested. The general result was that the longer the side chain, the better the performance.