Agriculture Reference
In-Depth Information
Delphinium
flowers are sensitive to ethylene, which is produced in the pistil and recepta-
cle, and causes abscission of the sepals, posing a serious problem in marketing.
Delphinium
hybrid
cv. Bellamosum flowers show a climacteric-like rise in ethylene production before
the abscission of sepals, and sepals are abscised by exposure to exogenous ethylene. Gy-
noecia and receptacles are the main ethylene producers in flowers, and the sepals, which are
most influenced by ethylene, are abscised after the peak in ethylene production (Ichimura
et al., 2000). The rate of senescence of
Delphinium
florets seems to be well correlated to
both ethylene production and levels of
Dl-ERS1
, suggesting that ethylene evolved by the
florets is perceived by elevated levels of
Dl-ERS1
to cause senescence of florets in
Del-
phinium
(Kuroda et al., 2003). On the other hand,
Dl-ERS1-3
and
Dl-ERS2
mRNAs were
upregulated by ethylene in
Delphinium
sepals, but did not change markedly during flower
senescence (Tanase and Ichimura, 2006).
In geranium (
Pelargonium
hortorum
) flowers, the levels of
Ph-ETR1
and
Ph-ETR2
transcripts were not upregulated by exogenous ethylene and did not change during flower
senescence.
Ph-ETR1
and
Ph-ETR2
were not affected by ethylene exposure in receptacles
containing abscission zones (Dervinis et al., 2000).
With respect to the role of ethylene in flower opening of cut roses, it has been reported
that flower opening is ethylene-influenced, and the effect of ethylene is cultivar-dependent,
and that the cultivars can roughly be divided into three groups: opening inhibited, open-
ing stimulated, and opening not affected by ethylene (Yamamoto et al., 1994). The level
of mRNA for an ethylene receptor (RhETR2) in petals of rose (
Rosa hybrida
) flowers at
the full-opening stage was two times higher in “Bronze” cultivar, which has a short floral
life and sensitive to ethylene, than that in “Vanilla” cultivar, a cultivar less ethylene sensi-
tive with a long floral life (Muller et al., 2000). While
RhETR2
expression varied during
flower development and in response to ethylene,
RhETR1
and
RhETR3
exhibited differential
expression during flower development and appeared to be rate limiting for ethylene percep-
tion and determinants of flower longevity. Expression of
RhETR1
was distinctly higher in
“Bronze,” than in “Vanilla.” While expression of RhETR1 preceded the ethylene production
by the flowers, abundance of the
RhETR3
transcript increased during flower senescence in
“Bronze,” indicating that the ethylene response system in rose flowers is composed of mul-
tiple receptor types with overlapping patterns of expression. In “Vanilla,” a cultivar that has
excellent flower longevity despite moderate ethylene production, expression of
RhETR1
and
RhETR3
was reduced. In another study involving two ethylene-sensitive cut rose flowers
“Kardinal” and “Samantha,” expression level of the three
ETRs
—
Rh-ETR1
,
RhETR3
, and
RhETR5
—was higher in “Samantha” than in “Kardinal,” indicating that higher ethylene
sensitivity of “Kardinal” is probably due to its lower expression level of ethylene receptors
during the flower opening process (Tan et al., 2006). These results suggested that differences
in flower life among rose cultivars—in an ethylene-free environment and in response to ex-
ogenous ethylene—may be due to differences in receptor expression levels. In “Samantha,”
Rh-ETR5
was found to be constitutive and ethylene-independent, whereas
Rh-ETR1
and
Rh-ETR3
were induced by ethylene and suppressed by 1-MCP (Ma et al., 2006b).
In carnation flowers (
Dianthus caryophyllus
), the levels of
DC-ERS2
and
DC-ETR1
mRNAs in petals increased with an increase in ethylene production. However, ethylene
treatment did not affect the levels of these mRNAs in petals. Furthermore, the levels of
these mRNAs decreased independent of ethylene production in petals of flowers treated
with DPSS (1,1-dimethyl-4-(phenylsulfonyl)semicarbazide, a putative inhibitor of abscisic
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