MSc

A study was conducted at the Department of Horticulture,
College of Agriculture, Vellayani from September 1996 to January 1997 to
find the effects of various postharvest chemical treatments in improving
quality and vase life of Dendrobium cut-flowers and to identify the best
combination of chemicals for maximising vase life. The study comprised
of four experiments. All of them were laid out in Completely Randomised
Design except the fourth which was in factorial CRD.
The conditioning treatments, pulsing and use of holding solutions
were significantly influence the vase life of Dendrobium varieties. The
best conditioning treatments observed in Expt.l were tap water altered to
pH 3.0 (T 4) and 3.5 (T 3) which recorded a vase life of 20.67 days and
19.67 days respectively. Changes in the fresh weight, dry weight, water
content, sugar content and flower size during vase life period were not
influenced by the conditioning treatments. Irrespective of the treatments
the fresh weight of the inflorescences increased upto the fourth day and by
the seventh day a decline proceeded upto the cessation of vase life. So
also the flowers were found to maintain their maximum length and width
upto the seventh day of the vase life period. In experiment 2, pulsing with
a combination of 4% sucrose and 400 ppm 8-HQ for six hours was found

to result in the highest vase life of 21.33 days in packed inflorescences
subjected to a period of transport and transit (simulated) for 24 hours.
Irrespective of the pulsing treatments, changes in fresh weight and flower
structure followed the same pattern as in the conditioned inflorescences of
experiment 1.
In experiment 3.1, the freshly harvested inflorescences conditioned
for two hours in tap water of pH 3.0 were subjected to the holding solution
treatments. Vase life was the highest (26 days) in T 22 (6% sucrose + 300
ppm 8-HQ + 20 ppm AgNO3 followed by T 27, T 17 and T 21. In the
conditioned and pulsed inflorescences subjected to the simulation of transit
and transport for 24 hours followed by treatment in holding solutions (Expt.
3.2), the vase life was the highest in T 8 (2% sucrose + 400 ppm 8-HQ +
30 ppm AgNO3), T 9 (2% sucrose + 400 ppm 8-HQ + 40 ppm AgNO3), T 11
(4% sucrose + 200 ppm 8-HQ + 30 ppm AgNO3), T 15 (4% sucrose + 300
ppm 8-HQ + 40 ppm AgNO3), and T 17 (4% sucrose + 400 ppm 8-HQ +
30 ppm AgNO3). The sucrose concentration of the treatments which
resulted in a high vase life was generally lower for the pulsed flowers
when compared to the non-pulsed flowers of experiment 3.1. In both the
groups, irrespective of the treatments, changes in flower structure measured
as changes in the maximum length and width of the flowers, were noticed
during the vase life period.
The fourth experiment was carried out to test the applicability of
the results of the experiments 1, 2, 3.1 and 3.2 in three other popular

cultivars namely, Dendrobium Mary Trowse, D. Candy Stripe and D. Waiter
Oumae. The vase life of all the varieties were increased by the treatments
T 1 to T4 when compared to the control (T5). In D. Walter Oumae a
greater vase life was observed in flowers subjected to conditioning followed
by pulsing (T 2), conditioning, pulsing and holding in 6% sucrose + 300
ppm 8-HQ + 20 ppm AgNO3 (T 3) and conditioning, pulsing and holding
in 2% sucrose + 400 ppm 8-HQ + 30 ppm AgNO3 (T5) than the control
(T 5). In Dendrobium Mary Trowse, T3 and T4 recorded a greater vase life
and in D. Candy Stripe, conditioning alone (T1) and T3 were observed to
result in a greater vase life. The sugar content of the flowers observed at
the cessation of vase life was also influenced by the treatments.
The electrical conductivity of the holding solutions was not observed
to be in the detectable range during the vase life period. Spike bending
was not observed in Dendrobium Sonia and other varieties. The petal
colour variations irrespective of the treatments recorded from the start to
the cessation of vase life showed that in the coloured cultivars namely
Dendrobium Sonia, Dendrobium Mary Trowse and Dendrobium Candy
Stripe, the petal colour deepened before browning, while in the Dendrobium
Walter Oumae, in the absence of colouring pigments, the loss of white
colour and the onset of browning was gradual.