Effect of Some Presowing Treatments on Germination of Bauhinia rufescens Seeds
G.C. van der Puije,
The study aimed at investigating the effect of chemical pre-sowing treatments
on the germination of Bauhinia rufescens seeds. The pre-sowing treatments
were made up of five different dilutions of concentrated sulphuric acid (10,
30, 50, 70, 90%), gibberellic acid (0.01, 0.03, 0.05, 0.07, 0.09) and potassium
nitrate (0.1, 0.3, 0.5, 0.7, 0.9) and a control treated with distilled water.
Pure seeds of Bauhinia rufescens were soaked in the various dilutions
of sulphuric acid for 30 min while that of gibberellic acid and potassium nitrate
were soaked for 24 h. The control was soaked in distilled water for all the
respective treatments. The study lasted for 12 days during which data was collected
daily on germination which was used to calculate germination capacity, germination
value, germination rate, germination energy and coefficient of velocity of germination.
Data was analysed using general analysis of variance at 5% significance level.
There were significant differences between the treatments and interactions between
the treatments and sub-treatments including the control were also significant.
Sub-treatment 5 of treatment 1 (sulphuric acid) produced the highest germination
capacity of 93.8% and had the highest germination energy at 7, 10 and 12 days
after sowing. It produced the lowest germination rate at 25, 50 and 75% and
had the highest coefficient of velocity of 69. Other sub-treatments which also
had high germination capacity were sub-treatment 4 of treatment 1 (89.0%), sub-treatment
5 of treatment 2 (88.5%), sub-treatment 4 of treatment 2 (76.5). Germination
capacity increased with increasing concentration for all treatments. Only sub-treatments
5 and 4 of treatments 1 and 2 attained 75% germination rate. The results showed
that Sulphuric acid at 90% concentration was the most effective pre-sowing treatment
for the germination of Bauhinia rufescens seeds followed by 70% concentration
and that potassium nitrate was the least effective.
Received: November 07, 2011;
Accepted: March 05, 2012;
Published: June 21, 2012
Bauhinia rufescens Lam. is a popular ornamental plant in Ghana used
for the establishment of hedges, edges and to a less extent as small trees in
ornamental gardens (Asiedu et al., 2011). The
plant is propagated by seed (Connor, 2008; Le-Houerou,
2005). It is a hard seeded fabaceae which produces seeds with tough and
hard seed coat (Connor, 2009). This condition does not
encourage even germination but rather results in erratic germination of seeds
(Alderete-Chavez et al., 2011). To achieve rapid
and synchronous germination artificially, therefore, the seeds must be subjected
to some physical or chemical treatment (Islam et al.,
2009) thus the need to investigate pre-sowing treatments which can best
enhance germination (Butola and Bedola, 2004). Studies
by Anonymous (1998), Connor (2008)
and Asiedu et al. (2011) suggested treatment
of seeds with boiling water and scarification with 97% sulphuric acid to enhance
Several other pre-sowing treatments have been suggested to enhance germination
in hard seeded seeds. These include gibberellic acid, potassium nitrate (Alves
et al., 2000), succinic acid (Ghadiri and Torshiz,
2000); HCl, nitric acid, boric acid, acetic acid, ethanol, methanol, benzene,
xylene (Idu et al., 2007); thiourea, benzyl adenine
(Schmidt, 2000), among others.
As has been noted by Orwa et al. (2009) and Asiedu
et al. (2011) very little work has been done on the plant thus the
need to conduct further study to determine the maximum number of seeds which
can germinate under optimum conditions (Willan, 1987).
This experiment was thus conducted to investigate the effect of some pre-sowing
treatments on the germination of seeds of Bauhinia rufescens.
MATERIALS AND METHODS
Location of project: The experiment was conducted at the Department of
Crop Science laboratory in the Technology Village, a teaching and research facility
of the School of Agriculture, University of Cape Coast from February to May,
Preparation of pre-sowing treatments: Pure seeds of Bauhinia rufescens
were subjected to a total of 16 treatments using various dilutions of Sulphuric
acid, Potassium nitrate and gibberellic acid and distilled water as the control.
Seeds and other materials used were sterilized as recommended by Keshtkar
et al. (2008) and ISTA (1999).
Five different concentrations of sulphuric acid, potassium nitrate and gibberellic
acid (GA3) were prepared. The sulphuric acid concentrations were
prepared from a 97% conc. Sulphuric acid by diluting 9.8, 29.4, 49, 68.6 and
88.2 mL of the acid in 100 mL of distilled water to obtain 10, 20, 50, 70 and
90% dilutions, respectively. The potassium nitrate concentrations were prepared
by dissolving 1, 2, 3, 4 and 5 g in 1 L of distilled water to produce 0.1, 0.2,
0.3, 0.4 and 0.5% dilutions, respectively.
The GA3 concentrations were also prepared by dissolving 0.1, 0.3,
0.5, 0.7 and 0.9 g of Gibberellic acid in 1 L distilled water to yield 0.01,
0.03, 0.05, 0.07 and 0.09% dilutions, respectively (Table 1).
Treatment of seeds: Each treatment consisted of one hundred pure seeds
of Bauhinia rufescens repeated four times. Seeds were laid in petri-dishes;
25 seeds per petri-dish. For sulphuric acid treatment, seeds were immersed in
each of the respective concentrations (10, 20, 50, 70, 90%) and shaken with
a mechanical shaker for 30 min. The seeds were decanted and rinsed several times
under running tap water followed by distilled water after which they were laid
on moistened tissue paper in petri-dishes. Potassium nitrate treatments had
seeds soaked in each of the 5 dilutions (0.1, 0.2, 0.3, 0.4, 0.5%) for 24 h
(Keshtkar et al., 2008) at room temperature.
|| Summary of treatments
The treated seeds were then rinsed with distilled water, laid on a moistened
tissue paper in petri-dishes. For the GA3 treatments, pure seeds
were soaked in each of the respective concentrations (0.01, 0.03, 0.05, 0.07,
0.09%) for 24 h at room temperature (Chuanren et al.,
2004) after which the treated seeds were washed with distilled water before
they were laid on moistened tissue paper in petri-dishes. The control had pure
seeds of Bauhinia rufescens soaked in clean distilled water for all the
respective treatments (Table 1). The seeds were decanted and
put in sterilized petri dishes lined with moistened tissue paper. The control
also had 100 seeds and was repeated four times.
Experimental design: The experiment was laid out in a completely randomized
design and was carried out in series; repeated four times. A total of 400 seeds
was allocated to each treatment (ISTA, 1999).
Data taken: Data was taken on days to first germination; Number to first
germinate; Daily germination; cumulative germination percentage.
Germination assessment: The effects of pre-sowing treatment were assessed
by daily counting of number of germinated seeds. Germinated seeds were counted
and removed from the date of sowing until there was no more germination. A seed
was considered to have germinated when the tip of the radicle emerged free of
the seed coat (Wiese and Bining, 1987; Auld
et al., 1988). Daily germination percentage was summed up to obtain
cumulative germination on each assessment.
Germination period was determined as the number of days from first observed
germination to where there was no more germination but energy period was arbitrarily
defined in 12 days (Willan, 1987, 1993).
Germination pattern was also determined by number of seeds that germinate at
the different days after sowing (Viswanath et al.,
Germination energy defined as the percentage by number of seeds in a given
sample which germinate within a definite period such as 7-14 days under optimum
or stated condition (Willan, 1987) was determined. Germination
energy is also a measure of the speed of germination and hence, a measure of
the vigour of seedlings (Willan, 1993). In addition,
germination value which is a composite value that combines both germination
speed and total germination was also determined. Germination value is an objective
means of evaluating results of a germination test and is calculated using the
formula proposed by Hartmann et al. (1997) as follows:
Gv = (final) MDGxPV (MDG)
||(Final) Mean daily germination
||Peak value mean daily germination
Total germination is expressed as (final) Mean Daily Germination (MDG), calculated
as the cumulative percentage of full seed germination at the end of the test
divided by the number of days from sowing to the end of test period. Speed of
germination was determined and expressed as peak Value, which is the maximum
mean germination reached at any time during the period of the test (Willan,
The germination rate was calculated according to Wiese
and Bining (1987) as follows:
||Days after sowing
Coefficient of velocity of germination was also determined using the formulae
(Hartmann et al., 1997):
Germination pattern: Generally germination started early; most treatments
took 4 days to germinate. The only exceptions were in the sulphuric acid treatments
where sub-treatments 4, 5 and 6 which started germinating 3 days after sowing
(Fig. 1). Sub-treatments with higher concentrations (such
as sub-treatments 3, 4, 5) showed quick and spontaneous germination after an
initial delay. Lower concentration sub-treatments (sub-treatments 1, 2, 6) were
more gradual but slow. Although, there was no clear pattern between concentration
and number of days it took seeds to start germinating, germination increased
with increasing concentration for all sub-treatments (Table 2).
Also most sub-treatments reached their peak germination between 8-10 days after
|| Germination pattern showing relationship between treatments
|| Cumulative mean germination of sub-treatments and their significance
|Trt. 1, 2, 3: Sulphuric acid, potassium nitrate and gibberellic
acid treatments, respectively. Subtrt. 1, 2, 3, 4, 5: Five sub-treatment
levels for each of the treatments, DAS: Days after sowing
Germination and energy period: Ranged between 8-10 days with most treatments
taking 9 days after sowing to complete germination. Almost half of the sub-treatments
completed their germination period within the arbitrarily chosen 12 day test
period (Table 2). Those which could not attain like sub-treatments
1, 2 and 6 were assessed based on their energy period. Generally, the higher
concentrated sub-treatments (sub-treatments 4, 5) took a shorter period to attain
germination period than the lower concentration sub-treatments (sub-treatments
Germination capacity/percentage (GC): Cumulative germination percentage
for the sub-treatments ranged between 9.8 and 93.8. Sub-treatments 6 of T3 and
sub-treatment 5 of T1 produced the lowest and the highest, respectively (9.8,
93.8%). Germination capacity for sub-treatments with higher concentration (sub-treatments
4, 5) was far higher than those with lower concentration (ranging between 9.8-39.8%).
Sub-treatments 4 and 5 of T1 had the highest value (89.0, 93.8%) followed by
T2 (76.5, 88.5) and T3 (60.5, 67.3), respectively (Table 2).
Generally the interactions between means of treatments and their sub-treatments
including the control showed significant differences at 5% (Table
3). Treatment two (T2) produced the highest combined mean germination of
34.67% while T3 produced the lowest of 28.7% at a co-efficient of variation
of 1.7% (Least significant difference = 0.860).
|| ANOVA showing relationship between treatments, sub-treatments,
days after sowing (DAS) and interactions @5%
|Trt: Treatment, pr: Probability, DAS: Days after sowing
|| Germination energy at 7, 10 and 12 days after sowing (DAS)
Germination energy: Germination energy was determined at 7, 10 and 12
days after sowing and ranged between 2.8-89.5, 7.5-93.5 and 9.8-93.8%, respectively.
At all the germination energy levels the sub-treatment 6 produced the lowest
while sub-treatment 5 of T1 produced the highest values (Table
4). Generally germination energy values increased with increasing concentration
for all treatments but sub-treatments 4 and 5 of T1 showed the most dramatic
increase followed by T2.
Rate of germination: This was calculated at 25, 50 and 75%. The results
ranged between 3 and 12 days for 25%. With the exception of sub-treatment one
of T1 and sub-treatment 6, of T1, T2 and T3,
all treatments achieved 25% germination. The earliest was sub-treatment 5 of
T1 which achieved 25% germination less than 3 days after sowing while sub-treatment
2 was the last at more than 12 days after sowing. For 50%, the results ranged
between 3.4 and 10.8 days after sowing and more than half of the sub-treatments
did not achieve 50% germination (Table 5). The first to achieve
was sub-treatment 5 of T1 at 3.4 days while sub-treatment 3 of T3 was the last
at 10.8 days after sowing. Only a few sub-treatments; 4 and 5 of T1 and sub-treatment
4 and 5 of T2 achieved 75% germination. The first to achieve was sub-treatment
5 of T1 while the last was 4 of T2.
Germination value: The germination values were small and ranged between
1.1292 for T3 and 1.3090 for T2. This corresponded with a reverse but higher
mean daily germination of 4.167 and 4.258 for T2 and T3, respectively (Table
Coefficient of velocity: Ranged between 35.7 and 69.02. Sub-treatments
6 (control) and 5 of T1 had the lowest and highest values, respectively and
showed a regular pattern with increasing concentration. The trend did not follow
in the other treatments. Although sub-treatments 6 and 5 of T2 had the lowest
and highest values, respectively, sub-treatment 3 had a higher value than 4.
Also sub-treatment 1 of T3 had the lowest value within T3 but the highest was
sub-treatment 4 (Table 7, 8).
|| Germination rate for treatments
|| Germination value for treatments
|| Determination of coefficient of velocity (CV)
|| Determination of coefficient of velocity
Willan (1987) had suggested the use of energy period
as an alternative to germination period in situations where allowing all germinable
seeds to germinate could unduly prolong the test period resulting in poor vigour
seedlings. The early germination and the short period it took treatments to
attain germination period shows a significant improvement over earlier works
by Asiedu et al. (2011), who reported 6-8 days
in a work where hot water was used and Anonymous (2011)
who reported a germination period of 21-42 days. A high germination capacity
is indicative of high vigour and high field emergence compared with a low germination
capacity seen in delayed germination. Treatments with lower germination capacity
have lower competitive ability than early emerging once (Pourhadian
and Khajehpour, 2010). High germination capacity seen in sub-treatments
4 and 5 of T1 and T2 resulted in rapid and synchronous germination, suggesting
that their pre-sowing treatments were more effective (Islam
et al., 2009). The high germination capacity observed in the sub-treatments
with increasing concentration is also supported by Rahnama-Ghahfarokhi
and Tarakkol-Afshari (2007) and Muhammad and Amusa (2003)
who worked on GA3 and sulphuric acid, respectively and observed increased
germination capacity with increasing concentration. Schmidt
(2000) adds that sulphuric acid is the most effective pre-sowing treatment
for a hard seeded fabaceae like Bauhinia rufescens and that its ability
to increase germination capacity at higher concentrations is because it is able
to rupture the seed coat sufficiently to allow imbibitions. Effect at lower
concentrations though is the reverse (Keshtkar et al.,
2008; Muhammad and Amusa, 2003). Germination energy
is a measure of speed of germination with a lower value indicative of vigorous
seedlings. Sub-treatments of T1 which attained the highest germination capacity
within few days of sowing had lower germination energy and have better chances
of survival compared with those which had lower germination capacity (Willan,
1987). Also sub-treatment 5 of T1 which took fewer days to attain 25, 50
and 75% germination rate exhibited greater energy period. Coefficient of velocity
of germination increases as more seeds germinate and with shorter germination
time (Busso et al., 2005) and decreases as less
seeds germinate and with a higher germination time (Isfahan
and Shariati, 2007). The lower the value the lower the germination capacity
and the longer it takes for seeds to germinate as seen in sub-treatments 1 and
6. Thus, sub-treatment 5 of T1 which had the highest coefficient of velocity
of germination, is considered to be a better treatment with a better effect
on germination than the other sub-treatments.
There were significant differences between the three main treatment types T1
(sulphuric acid), T2 (gibberellic acid) and T3 (potassium nitrate) and within
treatments. The interactions between sub-treatments and treatments were also
significant. Sub-treatment 5 of T1 out-performed all the other treatments by
attaining the highest germination capacity of 93.8%, the highest germination
energy at 7, 10 and 12 days after sowing, the lowest germination rate at 25,
50 and 75% as well as the highest coefficient of velocity of germination of
69. Other sub-treatments which also performed well were sub-treatment 4 of T1
(89.0% germination capacity) and sub-treatment 5 of T2 (88.5% germination capacity).
The results confirmed earlier observations that germination capacity and other
germination assessment parameters improves with increasing concentration where
chemical pre-sowing treatments are used and that high concentrations of sulphuric
acid provide the most effective pre-sowing treatment in hard seeded seeds. Finally
the results showed that potassium nitrate was the least effective chemical pre-sowing
treatment compared with sulphuric acid and gibberellic acid in the germination
of Bauhinia rufescens seeds.
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