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Simple methods of breaking dormancy of passion fruit seeds for resource
restrained nurserymen in remote Africa
Niwarinda Jasper1 and Nyamweha Bruce Robin1
1School of Agriculture and Environmental sciences, Mountains of the Moon University P.O Box
837 Fort Portal, Uganda.
ABSTRACT
Passion fruits are among the fruits on high demand in Uganda and international markets. The
challenge with passion fruit production is that their seeds are characterized by hard seed coat
which inhibits the embryo to access water and oxygen. This leads to delay in germination or
failure of seeds to germinate in nursery so nurserymen fail to raise the target seedlings. This
study aimed at assessing the low cost methods of breaking dormancy of passion fruit seeds. The
study tested use of hot water, citric acid, sucrose solution as measures to break seed dormancy of
passion seeds in comparison with control seeds (untreated). After the seed treatment, seeds were
sown in the nursery bed in 4 replications at the Horticulture demonstration unit of Mountains of
the Moon University. The data was collected as germination percentage, duration and vigor.
Analysis done with aid of Genstat software to perform one-way ANOVA to identify significant
differences in germination percentage and vigor among the seed treatment methods.
Seeds soaked in soaked in citric acid had the highest germination percentage with 82.6% and
lowest germination percentage in control seeds with 8.0%. There were significant differences in
germination percentage among treated seed samples with p value less than 0.05 (one-way
ANOVA).
Based on the finding, the three methods tested in the study i.e. Using citric acid, use of sucrose
solution and hot water proved very effective methods of breaking seed dormancy of passion
fruits. Citric acid was the most effective method as characterized by high germination and early
germination. There is need to try citric acid on seeds of other species of passion fruit.
Key words: seed dormancy, dormancy measures, passion fruit, affordable methods.
INTRODUCTION
Passion fruit is scientifically known as Passiflora edulis belonging to the plant family of
passifloraceae (https://plants.usda.gov/java/ClassificationServlet) and (Morton, 1987).There are
two major varieties of the crop i.e. purple and yellow/gold varieties (Morton, 1987). Purple
variety is the most cultivated in Uganda probably due to its high demand in the market and
fetches good price (Kato, 2014 and Bbosa, 2018). Passion fruit seeds have a hard seed coat
hinders the embryo to access to water and oxygen necessary for its germination (Rego et al,
2014, Marostega, et al, 2017 and Marina, 2018). Several methods are used to break this kind of
seed dormancy such as use of sulphuric acid, physical scarification, gibberellic acid and
KNO3(Manoel et al,2010, Marostega, et al, 2017, Marina, 2018, Pallavi et al,2014). Some are
difficult for nursery men to implement due to skills and resources associated with the methods.
This study experimented methods whose materials locally available to the small scale nursery
operators. These methods were use of citric acid, using sucrose solution and hot water
treatment.
MATERIALS AND METHODS
Description of experiment
This experiment assessed 3 treatments on passion fruit seeds: soaking passion fruit seeds in
undiluted citric acid, some seeds soaked in 10% sucrose solution, Other seeds were subjected to
hot water at temperature of 70oC for 10 seconds and control seeds which were not treated. After
carrying out the treatments, seeds were sowed in sandy loam seed bed so that seedlings can
easily emerge. This was done at Horticulture demonstration unit in Mountains of the Moon
University. Seeds of each treatment were sown in 4 replications in a randomized complete block
design (figure1).
Figure 1. Sowing of passion seeds in the seed bed after treatment.
Seed extraction
The seeds used in the experiment were extracted from purple passion fruits variety bought from
the farmers’ market in Kabudaire Fort Portal municipality. Ripe fruits were split open and seeds
were removed. This was followed by washing the seeds with rain water to remove pulp to
enhance effectiveness of seed treatments. Finally wiping of seeds with a cloth to further remove
the residues of pulp from the seeds.
Application of the treatments
For citric acid treated seeds, the juice was extracted from lemon fruits by pressing the fruits after
half cut. Seeds were soaked in concentrated lemon juice with no water added to dilute it.
Soaking of seeds was done for 15 hours and finally sowing of seeds next day.
Sucrose treated seeds: seeds were in soaked in 10% sucrose solution over night . The solution
was prepared by adding 10 gram of sucrose sugar into 100 grams of water. Therefore a digital
scale was used to determine such amount of sugar in water. Soaking seeds was done for 15 hours
and sowing followed next day.
Hot water: the rain water was boiled and cooled to 70oC with cold water after seeds subjected to
that water for 10 seconds. Immediately sowing was done in the seed bed.
Some seeds were not soaked in citric acid, sucrose solution and subjected to hot water so they
were termed as control seeds. They were sown in the seed bed at the same time with treated
seeds to establish comparison standards.
Data collection and analysis
Data was collected in form of germination percentage (figure 2) the germination duration, and
germination vigor . Germination percentage (GP) was obtained by formula stated below:
Germination percentage = Number of germinated seedlings X 100
Total number of seeds sowed (25 seeds) per block.
For germination vigor obtained by measuring the weight of the 2 months old seedlings at the
end of the experiment using digital scale. While germination duration was determined by
considering how long seeds took to germinate.
Figure 2. Counting germinated seedlings to determine germination percentage
Soft ware Gen Stat the 18th edition was used to perform one way ANOVA to establish significant
differences in germination percentage and vigor among treated seed samples of passion fruits.
RESULTS
Germination percentage
Seeds treated with citric acid had the highest germination percentage with 82.67% and the
lowest in control seeds with 8% (figure 3) There were significant differences in germination
percentages among the treatments with p<0.05 (one way ANOVA) as indicated by different
letters in figure 3.
Figure 3. Mean germination percentage of passion fruit seeds with error bars stand for standard deviation
Germination vigor
The highest germination vigor was observed in the sucrose seeds with seedlings weight of 0.28
gram, and lowest was in control seeds with 0.07 grams (figure 4). There were no significant
differences in germination vigor among the treatments with P greater than 0.05 as indicated by
same letter in figure 4.
Figure 5.Mean germination vigor of passion fruit seedlings from treated seeds.
a
bb
c
0
10
20
30
40
50
60
70
80
90
100
Citric acid sucrose hot water control
Germination
percentage
Treatments of passion fruit seeds
a
a
a
a
0
0.05
0.1
0.15
0.2
0.25
0.3
Citric acid sucrose hot water control
Germination
vigor of passion
seedlings in
grams
Treatment of passion fruit seeds
Duration of germination
Seeds soaked in citric acid took the shortest time to germinate 20 days, hot water treated seeds
soaked in germinated in 22 days, sucrose treated seeds germinated in 24 days the control seeds
took the longest time 28 days to germinate after sowing as those seeds soaked in sucrose solution
took 24 days to germinate
Figure 6. Germination rate of treated and control seed samples
Height of seedlings
Seedlings treated with sucrose, were tallest 10.80 centimeters followed by seedling emerged
from hot water seeds 9.50 centimeters, then control seedlings 9.00 centimeters and the shortest
were seedlings from citric acid 8.40 centimeters (figure 7) There were no significant differences
among in seedlings’ height from different seed treatments with p greater than 0.05 as same letters
in figure 7.
0
5
10
15
20
25
18th
day
20th
day
22rd
day
24th
day
26th
day
28th
day
30th
day
32rd
day
Number of seedlings germinating
Days of sampling
Citric acid
Control
seeds
Hot water
Sucrose
Figure 7. Height of seedlings from different seed treatments
DISCUSSION
Effective methods in the study
Seeds treated with citric acid had the highest germination percentage of 82.67% and took the
shortest time to germinate 18 days. This can attributed to corrosive effect of acid on seed coat to
embryo to access water and oxygen (Eşen et al, 2009, Purohit et al, 2015 and Niu et al, 2018).
Therefore use of citric acid to break down dormancy of passion fruit seeds as the most effective
method. However, seedlings germinated from citric acid treated seeds had lower the vigor and
shortest seedlings as compared to the sucrose treated seed. This is because sucrose provides
carbon for seedling metabolism (Pinfield-wells et al, 2005) thus sucrose solution can break
immature embryo dormancy. Use of sucrose solution was more effective than hot water with
73.33% germination and seedling height of 10.4 centimeters.
Hot water treated seeds performed better than untreated seeds (control) 70.67% germination and
germinated in 22 days time. It can be explained by the fact that hot water softens the seed coat
for embryo to emerge out with less energy (McDonnell et al,2012).So it is necessary to carry out
that seed treatment . Control seeds had the poor germination of 8.00% germination and took the
longest time of 24 days to germinate.
a
aaa
0
2
4
6
8
10
12
14
sucrose hot water control citric acid
Height of
seedlings after
germination in
centimeters
Treatment of passion fruit seeds
CONCLUSION AND RECOMMENDATIONS
Based on the finding, the three methods tried in the study i.e. Using citric acid, use of sucrose
solution, hot water are very effective methods of breaking seed dormancy of passion fruits. Citric
acid was the most effective method as characterized by high germination and early germination.
Treating passion fruit seeds with sucrose solution produce quality seedlings compared to the use
of citric acid. There is need to try citric acid on seeds of other species of passion fruit.
REFERENCES
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