Partial vacuum DP = P
atmospheric
− P
actual
was obtained by lowering the actual pressure P
actual
at the upper end of the stem segment by a peristaltic tubing pump Watson-Marlow 505 Di,
Cheltenham, UK controlled by a personal computer. Actual pressure was measured using a
ceramic
pressure transducer
DVR 5,
Vacuubrand, Wertheim, Germany. Flow through the stem segments was calculated from weight
changes of a container filled with solution, in which the lower end of the stem segment was
placed. Composition of the solution was varied as mentioned for the individual experiments. Weight
of the container was measured on the balance coupled to the personal computer at a 1 s sample
rate averaged over 30 s. Measured flow rates were corrected
for direct
evaporation from
the container.
All sample preparation was done under the same solution as that used in the container to
prevent air-entrance into the vessels at the cut surface. Stems were cut into 20 cm long segments.
Leaves were removed from the stem segment with a razor blade, leaving 1 cm stubs of the petioles
on the stem. The upper side of the segments was inserted into silicon tubes also under solution and
attached to the measurement system. When hydraulic resistance was measured after several
days of vase life, the solution in the container during the measurement and the vase solution
during the vase life experiment were of the same composition. During preparation and during
change of solutions a small positive pressure due to gravity was applied to the tubing system
attached to the upper side of the stem segment to avoid air-entry at the basal cut surface.
2
.
7
. Bacteria In an experiment on the specific effects of
Cu
2 +
, bacterial numbers in vase solutions of NaHCO
3
plus CaCl
2
with and without CuSO
4
respectively, solutions 2 and 3; Table 2 were monitored after 2, 3, 4 and 6 days of vase life. A
third treatment involved treating the flowers in as sterile a manner as possible and placing them in
the solution without Cu
2 +
solution 2. In this treatment, the lower 15 cm of the stem was wiped
with a tissue saturated with 96 ethanol, Erlen- meyer flasks with vase solution were autoclaved
and during the vase life experiment the Erlen- meyer flasks were covered with aluminium foil.
Solution samples were diluted, plated onto Plate Count Agar Oxoid, Unipath, Hampshire, UK
and incubated at 27°C for 48 h before the number of colony forming units cfu was counted. These
numbers were expressed per millilitre of vase wa- ter.
2
.
8
. Statistical design In the vase experiments, the design was a ran-
domised complete block with 12 flowers per treat- ment. The flowers were placed in a climate room
with four blocks, and three flowers per treatment in each block. Within a block, the three flowers of
one treatment were grouped together to form one sample unit. Analysis of variance was applied to
relative fresh weight, average daily uptake and transpiration rate, followed by mean separation
according to Tukey’s HSD-test. Each treatment was
repeated at
least once
in a
separate experiment.
3. Results
3
.
1
. Effects of main components in tap water on water status
Fresh weight of cut chrysanthemum flowers placed in deionized water decreased from the sec-
ond day of vase life Fig. 1A, indicating a deteri- oration of their water status. During the 4 days of
the experiment, flowers in tap water increased in fresh weight Fig. 1A. The main components of
‘Wageningen tap water’ are HCO
3 −
and Ca
2 +
Table 1. Carbonate added to deionized water solution 1, Table 2 did not prevent the decrease
of the fresh weight of the flowers Fig. 1A. In addition, a solution with both HCO
3 −
and Ca
2 +
concentrations similar to tap water solution 2, Table 2 had no effect on the fresh weight of the
flowers as compared to deionized water Fig. 1A. Samples of tap water in our laboratory showed
the presence of a low amount of Cu
2 +
varying
between 0.006 mM at the beginning of the day and 0.002 mM after running the water for 1 h.
Adding 0.005 mM CuSO
4
to the mixture of NaHCO
3
+ CaCl
2
solution 3, Table 2 resulted in a fresh weight gain, similar to that in tap water,
during the first 4 days of vase life Fig. 1B.
3
.
2
. Specific effects of copper Replacing CuSO
4
in solution 3 Table 2 by CuNO
3 2
or CuCl
2
with the same amount of Cu
2 +
resulted in similar effects on fresh weight of the flowers during the first 6 days of vase life,
thereafter the experiment being terminated data not shown. Flower fresh weight change was not
significantly affected by leaving out Cu
2 +
from the solution if the flowers were treated in as sterile
a manner as possible Fig. 2A. The increase in number of bacteria in the vase water during vase
life was retarded by addition of CuSO
4
as well as by sterile handling Fig. 2B. There was a good
relationship between the number of bacteria and the daily increase in fresh weight of the cut flow-
ers Fig. 2C.
When one chrysanthemum flowering stem was held in 300 ml of vase solution, the threshold
concentration of Cu
2 +
for maintaining fresh weight was between 0.002 and 0.005 mM Table
3. Increasing the concentration further to 0.020 mM had no beneficial effect on the fresh weight
Table 3. None of the CuSO
4
concentrations used caused harm to flowers or leaves during the 7
days of the experiment, even when initial solution uptake was increased by dehydration to 5 of
their saturated fresh weight before the flowers were placed into the various concentrations.
3
.
3
. Specific effects of CaCl
2
and NaHCO
3
Copper sulphate alone had no significant effect on flower fresh weight compared to deionized
water Fig. 3. Calcium chloride as well as NaHCO
3
added to the CuSO
4
solution delayed the fresh weight decrease by some days Fig. 3.
However, the relative effects of the two compo- nents varied between various experiments. Adding
both salts with the CuSO
4
solution gave results that
were more
consistent across
various experiments.
3
.
4
. Water uptake, transpiration and hydraulic re- sistance
From day 2 of vase life, water uptake rate decreased for all solutions tested Fig. 4. Uptake
rate decreased fastest in deionized water, while flowers in the two solutions containing CaCl
2
showed the smallest decrease in water uptake rate from day 4 Fig. 4.
Fig. 1. Effect of various vase solutions on fresh weight during vase life. Flowers were placed in tap water , deionized
water ,
or a
solution of
NaHCO
3
+ CaCO
3
D, NaHCO
3
+ CaCl
2
2, or NaHCO
3
+ CaCl
2
+ CuSO
4
. Salt concentrations were according to Table 2, solutions 1, 2,
and 3. A and B were two separate experiments. Relative fresh weights at the same day marked by the same letter or without
any letter are not significantly different from each other P B 0.05.
Flowers in a KCl solution with the same con- centration of Cl
−
solution 4, Table 2 as the CaCl
2
solutions used before, showed a fresh weight change pattern like flowers in the CaCl
2
solution Fig. 5A. The same observation held true for flowers in a KNO
3
solution equimolar to this KCl solution solution 5, Table 2. Increasing
the concentration of CaCl
2
five times affected fresh weight positively, especially after 5 days of
vase life Fig. 5A. This positive effect was not accompanied by an increased water uptake rate in
comparison to the lower concentration, but by a drastic decrease in average daily transpiration rate
Fig. 5B – C. The effect of the high concentration of CaCl
2
on transpiration was confirmed by short- term
transpiration measurements
data not
shown. Approximately 1 h after placing the flow- ers in the Ca
2 +
solutions, transpiration rate started to decrease with the high concentration
10.7 mM. Compared to deionized water, there were no significant effects on short-term transpi-
ration rates of the low CaCl
2
concentration 0.7 mM, NaHCO
3
1.5 mM, or the combination of both solution 3, Table 2, all including CuSO
4
0.005 mM data not shown. Hydraulic resistance of the stem including the
cut surface after 4 days of vase life in the mixture of NaHCO
3
+ CaCl
2
+ CuSO
4
was comparable to that in tap water, while in deionized water it
wasapproximately seven times the value in tap water Table 4. Calcium chloride solutions imme-
diately lowered hydraulic resistance of stem seg- ments from fresh cut flowers. Hydraulic resistance
decreased by 7 by 10 mM CaCl
2
Fig. 6. Solutions of KCl and NaCl equimolar to the
CaCl
2
solution as well as solution 3 Table 2 affected hydraulic resistance of stem segments
from fresh cut flowers to the same degree as 10 mM CaCl
2
data not shown. After 7 days of vase life in deionized water, hydraulic resistance of
stem segments not including the basal 3-cm part was approximately three times the resistance of
flowers placed in CaCl
2
solutions Table 5. Sodium bicarbonate did not affect the long-term
increase in hydraulic resistance during vase life,
Fig. 2. Effect of CuSO
4
and almost sterile handling on relative fresh weight A and number of bacteria in vase water B
during vase life. Panel C gives the relationship between num- ber of bacteria on days 2, 3, 4 and 6 from B and the daily
fresh weight increase computed as the difference in weight between the day bacteria were counted and the day before
from A. − Cu = solution 2 Table 2, + Cu = solution 3 Table 2, − Cu, sterile = solution 2 Table 2 including sterile
handling as described in Section 2. Fresh weights on the same
day marked by the same letter or without any letter are not significantly different from each other P B 0.05. Regression
line is y = − 1.00x + 5.50, R
2
= 0.78.
Table 3 Relative fresh weight after 7 days of vase life in solutions with
various CuSO
4
concentrations
a
Relative fresh weight Concentration CuSO
4
mM 0.000
93.1a 96.3ab
0.001 0.002
97.4b 102.2c
0.005 103.4c
0.010 103.2c
0.020
a
Copper sulphate was added to a solution of CaCl
2
and NaHCO
3
solution 2, Table 2. To simulate water loss during dry storage or transport, flowers were taken out of water for 1
h under vase life room conditions resulting in 5 weight loss before they were placed in the different solutions. Fresh
weights marked by the same letter are not significantly differ- ent from each other PB0.05.
whether the original cut surface was included data not shown or not Table 5 during the
resistance measurement.
4. Discussion
