DIFFERENT CULTIVARS OF CHRYSANTHEMUM HAVE INTRINSIC DIFFERENCES
IN WATER LOSING RATE
ANNELIES CHRISTIAENS1,2, BRUNO GOBIN2 and MARIE-CHRISTINE VAN LABEKE1
1
Ghent University-Faculty of Bioscience Engineering, Department for Plant Production, Coupure links 653, 9000 Gent, Belgium
2 PCS – Ornamental Plant Research, Schaessestraat 18, 9070 Destelbergen, Belgium
Introduction
The genus Chrysanthemum contains different hybrids and thousands of cultivars with ornamental value. The potplant selections of Chrysanthemum x morifolium have a
great economic value in Belgium. Through extensive breeding programs by Belgian companies, a continuous renewal of cultivars is introduced to the market. The different
cultivars are not only phenotypically different, but will also have genotype differences which might result in different responses to abiotic stress.
In order to cope with the seasonal nature of Chrysanthemum production and therefore the peak periods with a high demand of cuttings, cuttings can be harvested and
stored for several days until the rooting phase can start. However, storage implies some drawbacks, one of which includes the loss of turgidity. In order to obtain an idea of
the possible cultivar differences to maintain their water balance, we screened 25 cultivars. We optimized a standard protocol to determine the water losing rate (WLR).
Determination of WLR for cuttings
Screening of 25 cultivars
Take a cutting (4 leaves) from a stock
plant at a predefined time of day
→ weigh immediately
0.7
hi
ghi
fghi
fghi
fghi
fghi
fghi
fghi
fgh
efgh
defgh
defg
defg
defg
defg
cdef
cdef
bcd
abc
abc
ab
0.3
a
-1
0.4
cdef
0.5
-1
WLR (g h g DW)
0.6
i
WLR
bcde
FW
0.2
0.1
Four hours in controlled conditions
(21°C, 50% RH, 40 µmol/m².s)
W4
Leaf area
12
2
Leaf area (cm )
14
10
8
6
4
DW
Dry at 80°C for 24 h
0
cv 1
cv 2
cv 3
cv 4
cv 5
cv 6
cv 7
cv 8
cv 9
cv 10
cv 11
cv 12
cv 13
cv 14
cv 15
cv 16
cv 17
cv 18
cv 19
cv 20
cv 21
cv 22
cv 23
cv 24
cv 25
2
Fig. 1: Water losing rate (top) and leaf area (bottom) for 25 different commercial
Chrysanthemum cultivars (mean ± SE, n=10)
Calculate water losing rate
WLR (g
h−1g−1
FW − W4
DW) =
DW x 4
There is a strong difference in WLR between cultivars. The WLR of cultivars
with cuttings with a high water loss can be up to 2.5 times higher compared to
cultivars with cuttings with a low water loss; even though leaf area is similar
(Fig. 1). A possible explanation can be that water loss is closely regulated by a
high density of small stomata in cultivars with a low WLR (Table 1).
Table 1: Number of stomata and stomatal area of 2 Chrysanthemum cultivars with a low
WLR (cv 1, cv 2) and 2 cultivars with a high WLR (cv 20, cv 22) (mean ± SE, n=15)
The water losing rate is a measure for the speed with which plant parts lose
water. It is an easy, cheap and fast screening method to compare cultivars in
their ability to hold water.
However, it is a sensitive method as fresh weight decreases strongly the first
minutes and hours, so immediate weighing of the cutting after it has been cut
from the stock plant is necessary. Also care must be taken that conditions
during the 4 hours are closely monitored, differences in relative humidity or
temperature can result in a different WLR.
Cultivar
cv 1
N° of stomata
(n/mm²)
59.6 ± 1.2
Stomatal area
(µm²)
635 ± 21
cv 2
60.5 ± 2.3
640 ± 19
cv 20
46.9 ± 3.3
1016 ± 35
cv 22
46.2 ± 1.7
1019 ± 47
Conclusion
•
•
•
•
The water losing rate is highly cultivar dependent.
The WLR is not related to leaf area for the tested Chrysanthemum cultivars.
WLR seems to be related to the number and size of stomata. Cultivars with a high density of small stomata have a lower water losing rate.
The use of WLR can be an easy tool in breeding programs for fast screening of the water holding capacity of cuttings. Cuttings with a low WLR will be able to hold
turgidity longer during storage.