Agriculture Reference
In-Depth Information
(Damunupola & Joyce 2008). Flower containers such as
buckets need to be kept clean. Water temperature can affect
water uptake. Cold water has greater capacity to dissolve
gasses and may be less likely to give rise to air bubbles
blocking the xylem (i.e. cavitation) (Van Meeteren 1992;
van Doorn 1997). Conversely, warm water can facilitate
water uptake, possibly as a result of lower dissolved gas
content and / or reduced viscosity. Adjuvants that facilitate
water flow in stems include wetting agents (surfactants
such as Agral at 0.01% to 0.1% v/v; Table 19.3), acids (e.g.
citric acid; about pH 3.5) and germicides (Halevy & Mayak
1981; Faragher 1986; van Doorn 1997; Williamson &
Milburn 1995; Nell & Reid 2000; Reid 2002; Damunupola
& Joyce 2008). Commercial post-harvest solutions usually
contain germicides and acid, and sometimes wetting
agents, to improve water uptake. However, care should be
taken to avoid reactive constituents, such as chlorine with
citric acid (Xie
et al
. 2008).
Figure 19.8
Continued
Table 19.1
Temperature Effects on Respiration
and Heat Production by Carnation Flowers.
Temperature
(°C)
Anti-ethylene treatments
Pre-treatments to inhibit abscission and senescence are
commonly applied to ethylene-sensitive species (Halevy &
Mayak 1981; Wills
et al
. 1998; Reid 2002). A number of
ethylene sensitive flowers are listed in Table 19.4. Sources
of ethylene, such as ripening fruit and gas-powered forklifts
should be avoided. Ventilation with fresh air (more than
one room volume exchange per hour) is an effective and
inexpensive solution to ethylene contamination problems.
Inhibitors of ethylene production include AOA and
AVG. Inhibitors of ethylene action (i.e. binding) include
STS and 1-MCP (Figure 19.9). AOA can be used on species
that are affected by endogenous ethylene and which
tolerate this chemical, such as carnation. STS is widely
used, for example, on carnation, gypsophila, Geraldton
waxflower, sweet pea and solidago (Tables 19.5, 19.6 and
19.7). With the exception of 1-MCP, which is a gas, anti-
ethylene chemicals are usually applied as pulse treatments.
However, STS can be applied as a spray; for example, to
potted plants (Figure 19.9). A higher concentration of
STS is used for short (e.g. 15 minutes at 4 mM Ag
+
) versus
overnight (e.g. 0.5 mM Ag
+
) pulse treatments (Reid &
Farnham 1980; Joyce 1992; Faragher
et al
. 2002). It is
sometimes difficult in practice to ensure the flowers take
up the correct amount of STS. Because silver compounds
are toxic, STS requires careful handling and disposal. It
has been banned in most European countries (EC 2002)
and is not available in many states of the United States.
1-MCP is very effective at low concentrations and is
relatively easy and safe to apply and dispose (Nell & Reid
2000). In some flowers 1-MCP protects against ethylene
Respiration rate
(mg CO
2
/kg/h)
Heat production
(kW/t)
Q
10
0
10
0.026
—
10
30
0.079
3.0
20
239
0.632
8.0
30
516
1.364
2.2
40
1 053
2.784
2.0
50
1 600
4.245
1.5
(R2/R1)
10/(t2−t1)
is the factor by which reactions, in
this case respiration, increase with a 10°C increase in
temperature (Wills
et al
. 1998).
Source: Maxie
et al
. (1973), Hardenburg
et al
. (1986)
and Reid (2002).
Q
10
=
because moisture vapour in the thin boundary layer of high
humidity air in and around bunches is not swept away.
Cut flowers that have lost water can generally be
rehydrated by standing them in water (Halevy & Mayak
1981; van Doorn 1997; Wills
et al
. 1998; Reid 2002).
Cutting 2 to 3 cm from stems held under clean water can
remove air emboli blocking the xylem ends. However,
cutting stems under water is often not practical in large-
scale operations. Where water quality is poor (e.g. on-farm),
rain rather than dam water, removal of particulates (by
flocculation and filtering of clay) and disinfection to kill
microbes (by chlorination; Dychdala 1983; Haynes
et al
.
1990) are desirable. It is generally recommended that
flower water contains a germicide (biocide) or a commer-
cial post-harvest solution containing a germicide
