Agriculture Reference
In-Depth Information
compounds. For example, hypochlorite bleaching is most
efficient at pH 8.5 to 9.5. Interesting effects can be obtained
by allowing bleach solution to be taken up in the
transpiration stream via the stem (Plate 19.7). Bleaches are
caustic and so care must be taken with them, including the
use of protective clothing, respirators and ventilation.
item is also important in reaching and maintaining high
standards. Transport costs for dried flowers can be
relatively low if surface, rather than air, transport is used.
CONCLUSION
This chapter presents a general overview of the post-harvest
physiology and technology for cut flowers and foliage. For
the most part, each individual species has particular
characteristics that merit investigation if optimum post-
harvest longevity is to be realised (Halevy & Mayak 1981;
Reid 2004). The reader is therefore encouraged to research
the substantial published literature on cut flowers. The
following reference section contains relevant review articles
that cite numerous original publications on the many
different cut flower and foliage species.
Dyeing
Preserved cut flowers are typically immersed in textile
dyes, such as cationic aniline dyes, after initial processing
by bleaching (Dubois & Joyce 1989b; Joyce 1998). Dyes
are transparent, making prior bleaching particularly
important for darker plant materials. As dye compounds
generally do not bind specifically to plant material, the
degree of staining is a function of the plant material, dye
concentration and immersion time. Pure dyes can be mixed
to obtain different colours. However, they must be
compatible. For example, if anionic and cationic dyes are
mixed, they will precipitate. Dyes are usually toxic and so
appropriate material handling and safety literature must be
obtained.
REFERENCES
Ashman, T-L. & Schoen, D.J. (1994) How long should flowers
live?
Nature
,
371
, 788-791.
Beal, P., Howell, J., Joyce, D. & Young, K. (1998a)
Waxflower
harvest stages
. Publication QL98026. Department of
Primary Industries, Queensland, Australia.
Beal, P., Howell, J., Joyce, D. & Young, K. (1998b)
Waxflower
postharvest treatments
. Publication QL98025. Department
of Primary Industries, Queensland, Australia.
Beasley, D.R. & Joyce, D.C. (2002) A review of flower
characteristics of Geraldton waxflower and factors affecting
their abscission from harvested stems.
Australian Journal
of Experimental Agriculture
,
42
, 519-525.
Behe, B.K. (1993) Floral marketing and consumer research.
HortScience
,
28
, 11-14.
Behera, P.K., Sarangi, C.S., Mishra, D. & Patra, H.K. (1987)
Catalase, peroxidase and alkaline inorganic pyrophos-
phatase activities during petal development and senescence
in
Thevetia peruviana
(Pers.) K. Schum.
Israel Journal of
Botany
,
36
, 15-23.
Berkholst, C.E.M. & Navarro Gonzales, M. (1989) A simple
test for starch in rose petals.
Advances in Horticultural
Science
,
3
, 24-28.
Borochov, A. & Faragher, J.D. (1983) Comparison between
ultraviolet irradiation and ethylene effects on senescence
parameters in carnation flowers.
Plant Physiology
,
71
,
536-540.
Borochov, A., Spiegelstein, H. & Philosoph-Hadas, S. (1997)
Ethylene and flower petals senescence: interrelationship
with membrane lipid catabolism.
Physiologia Plantarum
,
100
, 606-612.
Borochov, A. & Woodson, W.R. (1989) Physiology and
biochemistry of flower petal senescence.
Horticultural
Reviews
,
11
, 15-43.
Bovy, A.G., Angenent, G.C., Dons, H.J.M. & van Altvorst,
A.C. (1999) Heterologous expression of the
Arabidopsis
Humectifying
Humectants are compounds, including polyols such as
glycerol, sugars, salts and quaternary ammonium comp-
ounds that absorb water from the atmosphere. As a result of
their hydration, they maintain treated plant tissue in a
supple (plasticised) state (Paparozzi & McCallister 1988;
Dubois & Joyce 1990, 1992b; Joyce 1998; Campbell
et al
.
2000). Glycerol (glycerine) is the most widely used
humectant. Humectants are applied either by uptake or
immersion. For immersion, the plant tissue can be pre-
treated with a strong alkali to strip the waxy cuticle and
thereby facilitate penetration. Treatment concentration,
time and temperature can affect the degree of humecti-
fication achieved. Under-treatment can leave the tissue
brittle. Over-treatment can result in a greasy product
predisposed to mould (Plate 19.7). Compounds that are
less water-attractive (e.g. low molecular weight polye-
thylene glycol) may be blended with glycerine to moderate
the degree of humectification. Humectification should be
undertaken with the typical temperature and RH conditions
of the intended marketplace in mind. Product packaged in
moisture-proof sealed bags is less likely to sweat during
transport to market.
Preserved cut flowers and foliage can be of lower unit
value than their fresh counterparts. Nonetheless, the supply
of uniform high quality preserved material is important.
Process monitoring and optimisation for each individual
