全 文 ：Journal of Forestry Research (2010) 21(3): 338−342
DOI: 10.1007/s11676-010-0068-1





Standardized pod collection time, pod length and pre-sowing treatment
of Albizia lebbeck at terai zone of West Bengal, India

Suman Malla • Gopal Shukla • Sumit Chakravarty




Received: 2009-07-28; Accepted: 2009-09-02
© Northeast Forestry University and Springer-Verlag Berlin Heidelberg 2010

Abstract : Three pod lengths (< 10 cm, 10–20 cm and > 20 cm) and 13
pre-sowing treatments were considered with four dates of collection (9
February, 19 February, 1 March and 11 March) to investigate their effect
on germination rate and growth of seedlings of Albizia lebbeck (L.)
Benth. at Pundibari, West Bengal, India. The best time of pod collection
was on 19 February as the germination rate of the seeds collected on this
date was 92.5% without requiring any pre-sowing treatments. This
clearly indicated that the seeds collected on 19 February were non-
dormant, viable and physiologically mature. Significantly better seedling
growth was also obtained when the seeds were sown on 19 February
which was extracted from pods of length 10-20 cm. Application of thio-
urea as a pre-treatment did not significantly enhanced seed germination
rate, but its application in lower concentration (100 μL·L-1) resulted in
better seedling growth and development.
Keywords: Albizia lebbeck; collection date; pod length; pre-sowing
treatment; germination; growth


Introduction

Albizia lebbeck (L.) Benth. is one of the important tree species in
arid and semi-arid regions of India (Anon 1983). It is a legumi-
nous and multipurpose species adapted to a wide variety of envi-
ronmental conditions because of its hardy nature. It nodulates
readily and its leaves are highly palatable and proteinaceous
(Prinsen 1986). A. lebbeck is a desirable species for energy plan-
tations because of its nitrogen fixing properties and green manur-
ing capabilities (Palani et al. 1996; Mutha et al. 2004). Due to its
multipurpose uses, A. lebbeck is a suitable tree species for farm
forestry plantations to be grown on field boundaries and hedges.
The quality demand for seed in raising commercial plantations is

The online version is available at http://www.springerlink.com
Suman Malla • Gopal Shukla • Sumit Chakravarty( )
Department of Forestry, Uttar Banga Krishi Viswavidyalaya, Pundibari-
736 165, Cooch Behar, West Bengal, India. E-mail: c_drsumit@yahoo.com
Responsible editor: Zhu Hong

increasing these days. Unfortunately in India, particularly in terai
region of West Bengal, there is no seed orchard of this species.
The seeds are collected from natural stands (Shukla et al. 2007).
At maturity stages, the pods harvested from the trees were found
significantly to influence germination of seeds in many species.
It is therefore, necessary to determine the optimum stage at
which the pods should be harvested from the trees (Bhardwaj
2001). Thus calendar date and pod length have been the impor-
tant parameters for determination of the optimum seed source
and maturity indices for better nursery performance.
An initial care is essential from the germination stage for A.
lebbeck because of its seed dormancy (Palani et al. 1996; Mutha
et al. 2004). Therefore, to facilitate germination in this species,
its seed must be placed in favourable environmental conditions
with adequate moisture supply, appropriate gaseous balance and
optimum light through chemical and mechanical scarification.
Treating with potassium nitrate or thiourea can also break the
dormancy of its seed (Heydecker and Coolbear 1977). As A.
lebbeck represents leguminosae family, its seeds are exogenously
dormant primarily due to its impermeable seed coat or pericarp.
Therefore, the characteristics of A. lebbeck impede proper and
complete germination of the seeds. Roy (1992) has successfully
attempted mechanical and chemical scarification for seed coat of
A. lebbeck through sulphuric acid, potassium nitrate and thiourea.
The present study was undertaken to standardize the date of pod
collection, pod length and pre-sowing treatments for proper and
optimum seed germination and seedling growth of A. lebbeck in
terai zone of West Bengal.

Methods and materials

Study area

This study was carried out in Central Forest Nursery, Department
of Forestry Uttar Banga Krishi Viswavidyalaya Pundibari at
Cooch Behar district of West Bengal state in India from February
to July, 2007. The experimental site was located at an elevation
of 43 m a.s.l., with sub-tropical climate receiving average annual
rainfall of 250−300 cm from south-west monsoon. About 80% of
ORIGINAL PAPER
Journal of Forestry Research (2010) 21(3): 338−342

339
this rainfall was received from June to August. The weather dur-
ing the study period was normal. The soil of the nursery was
from sandy to sandy loam with acidic reaction, low in organic
carbon, medium in available nitrogen and phosphorus and high
in available potash.

Fruit and seeds

About 50 trees of A. lebbeck were marked outside the university
campus for seed collection. The selected trees were at similar age
between 10 and 12 years. The trees initiated to flower on 27 of
July and the full bloom was recorded on 2 August. Pod formation
began about one month after flowering. The pods from these
trees were plucked in the four dates, i.e. on 9 February, 19 Feb-
ruary, 1 March and 11 March, 2007. The pods were graded as
three classes according to their length (less than 10, 10−20 cm
and more than 20 cm) before the seeds were extracted from them.

Pre-sowing treatments

The seeds were given the following pre-sowing treatments:
soaked in cold water for 24 h (T1); soaked in warm water for 24
h (T2); dipped in boiling water for 3 min, with subsequent cool-
ing for 24 h (T3); dipped in boiling water for 6 min with subse-
quent cooling for 24 h (T4); dipped in concentrated H2SO4 for 5
min, followed by washing and then soaking in cold water for 12
h (T5); dipped in concentrated H2SO4 for 8 min, followed by
washing and then soaking in cold water for 12 h (T6); soaked in
100 μL·L-1 thiourea for 12 h (T7); soaked in 200-μL·L-1 thiourea
for 12 h (T8); soaked in 300-μL·L-1 thiourea for 12 h (T9); soaked
in 100-μL·L-1 thiourea for 24 h (T10); soaked in 200-μL·L-1 thio-
urea for 24 h (T11); soaked in 300-μL·L-1 thiourea for 24 h (T12);
and no pre-sowing treatment or control (T13).
Hundred uniform seeds were sown immediately for each
treatment combinations after extraction of seeds from the graded
pods of every subsequent collection. Germination rate was re-
corded daily in the nursery beds till to 21 days. The data obtained
after seed germination were used to calculate the seed germina-
tion rate, germination capacity (GC), germination energy (GE),
germination value (GV), germination speed (GS) and seedling
vigour index (SVI). All these parameters were calculated follow-
ing the procedures of ISTA (Anon 1976). Seeds with 5 mm long
radicals were considered as germinated (Bhardwaj 2001).
Growth parameters like shoot and root length, shoot and root
diameter, shoot and root dry weight and root/ shoot ratio were
also recorded. The experiment was laid out in factorial random-
ized block design replicated thrice. The data were analyzed by
variance with the help of a personal computer (Gomez and Go-
mez 1984).

Results

Effect on germination

Date of collection
The germination of A. lebbeck was significantly influenced by
the dates of collection of pods (Table 1). The pods collected on
19 February (second collection) had the highest germination rate
(88.61%), followed by 61.67% on 1 March (third collection) and
least (34.72%) on 9 February (first collection). Similarly other
germination parameters were also significantly influenced by the
date of pod collection (Table 2).

Table 1. Effect of pod length and date of collection on germination
of Albizia lebbeck
Germination rate (%)
Pod length (cm)
Date of
collection
<10 10-20 >20 Mean
9 February 21.67 (27.68)* 42.50 (40.67) 40.00 (39-21) 34.72
19 February 84.17 (66.65) 92.50 (74.25) 89.17 (70-90) 88.61
1 March 55.00 (47.88) 65.83 (54.23) 64.17 (52.34) 61.67
11 March 33.33 (35.26) 40.00 (39.23) 38.33 (38.25) 37.22
Mean 48.54 60.21 57.92
Notes: CD (p = 0.05); Date of collection = 3.24; Pod length = 2.80.

Table 2. Effect of pod length and date of collection on germination
parameters of Albizia lebbeck
Date of collection GC GE GV GS SVI
9 February
53.33
(46.94)*
16.78
(23.80)
3.09 3.97 519.97
19 February
91.39
(73.34)
60.28
(51.29)
19.98 22.65 1406.16
1 March
70.56
(57.17)
42.50
(40.63)
8.97 8.87 1166.23
11 March
51.39
(45.79)
26.39
(30.73)
3.99 5.82 712.25
C D (p = 0.05) 3.29 10.86 1.07 1.16 92.85
Pod length (cm) GC GE GV GS SVI
< 10
61.46
(52.39)
31.96
(33.65)
7.42 9.55 851.10
10-20
71.04
(58.77)
42.50
(40.28)
9.96 11.01 1055.09
> 20
67.50
(56.27)
35.00
(35.91)
9.68 10.42 947.28
C D (p = 0.05) 2.85 9.40 0.93 1.00 80.41
Notes: GC is the Germination capacity, GE the Germination energy, GV the
Germination value, GS the Germination speed, and SVI is Seedling vigour
index. *Figures in parenthesis are ARC SIN values.

Pod length
Pod length had a significant effect on the germination of A. leb-
beck (Table 1). The highest germination rate (60.21%) was re-
corded when seeds extracted from pods of 10–20 cm long, fol-
lowed by the pods of > 20 cm in length (57.92%) while lowest
germination rate (48.54%) was recorded with pods of <10 cm in
length. Many reports supported that longer pods had bolder seeds
that gave better germination rates, such as Albizia chinensis
(Kumar et al. 2001; Bhardwaj et al. 2002b), Albizia procera
(Shukla et al. 2007), A. lebbeck (Roy 1985; Bhardwaj et al.
Journal of Forestry Research (2010) 21(3): 338−342

340
2002a; Mutha et al. 2004), Dalbergia sissoo (Kanak S. and Sahai
K. 1994), and Acacia nilotica (Bal Krishna and Singh 1995).
Similarly, pod length also had significant effect on the various
germination parameters viz. germination capacity, germination
value, germination speed and germination vigour except germi-
nation energy of A. lebbeck (Table 2).

Pre-sowing treatments
The seeds of A. lebbeck generally require some kinds of pre-
sowing treatments (Agboola et al. 2005). The highest seed ger-
mination rate (55%) was obtained by soaking the seeds in 200
μL·L-1 of thiourea for 12 h (T8), followed by thiourea of 100
μL·L-1 (T7) and 300 μL·L-1 (T9) for 12 h and cold (T1) and hot
water (T2) for 24 h (Table 3). Control (no treatments) has signifi-
cantly low germination rate, compared to T8, T7, T9, T1 and T2.
Seed germination rate was drastically reduced when the seeds
were dipped in concentrated acid for 5 min (T5) and 8 min (T6)
and also boiling water dip for 3 min (T3) and 6 min (T4). The
treatment T6 was most damaging, which resulted into the lowest
seed germination rate in all treatments (10.21 %). This might be
due to longer exposure of the seeds to these treatments, which
had partially or completely damaged embryo of seeds.

Interaction effect

Date of collection and pod length
Table 1 clearly indicated that the best seed germination rate
(92.50%) was obtained when the best date of collection (19 Feb-
ruary) was combined with the best length of pod (from 10 cm to
20 cm). Similar interaction effect was also observed for all the
germination parameters.

Date of collection and pre-sowing treatment
Significant interaction effects of sowing dates and pre-sowing
treatments were also recorded in Table 3. The effects of pre-
sowing seed treatments (T4, T5 and T6) were the worst, which
completely damaged the seeds with complete failure of germina-
tion. The seeds collected on 19 February had the best germina-
tion rate when exposed to the best pre-sowing treatments i.e. T7,
T8 and T9.

Table 3. Effect of date of collection and pre-sowing treatments on germination of Albizia lebbeck
Pre-sowing treatments Date of col-
lection T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 Mean
9 February
42.50
(40.66)*
37.50
(37.70)
4.18
(11.64)
0.00
(4.05)
0.00
(4.05)
0.00
(4.05)
47.50
(43.52)
49.17
(44.52)
38.50
(38.32)
13.33
(21.29)
17.50
(24.44)
16.67
(23.94)
68.33
(55.83)
25.78
(27.23)
19 February
60.00
(51.04)
68.33
(55.89)
43.33
(41.13)
15.83
(23.39)
46.50
41.44)
20.83
27.19)
87.50
(69.56)
82.50
(65.39)
75.00
(60.20)
56.67
(48.85)
65.83
(54.25)
74.17
(59.93)
33.33
(35.26)
56.14
(48.73)
1 March
54.17
(47.56)
46.83
(43.18)
38.33
(38.19)
18.33
(25.34)
48.33
(43.56)
23.33
(28.88)
54.17
(47.39)
51.67
(45.96)
52.67
(46.53)
38.33
(38.24)
46.67
(43.08)
38.33
(38.22)
23.83
(30.54)
41.31
(39.74)
11 March
40.83
(39.69)
44.17
(41.61)
20.00
(26.45)
6.67
(14.78)
19.17
(25.84)
20.83
(27.03)
25.83
(30.47)
36.67
(37.26)
32.50
(34.51)
26.67
(31.07)
38.33
(38.24)
31.67
(34.23)
22.50
(28.29)
28.14
(31.49)
Mean
49.37
(44.71)
49.21
(44.60)
26.46
(29.36)
10.21
(16.89)
28.50
(28.72)
16.25
(21.78)
53.75
(47.74)
55.00
(48.29)
49.67
(44.89)
33.75
(34.86)
42.08
(40.00)
40.21
(39.08)
37.50
(37.8)

Notes: * Figures in parenthesis are ARC SIN values; C D (p = 0.05); Date of collection = 3.68; Pre-sowing treatments = 6.64.

Effect on seedling growth

Date of collection
Seedling growth parameters of A. lebbeck were significantly
affected by the date of pod collection (Table 4). Root length, root
diameter, root dry weight, shoot length, shoot diameter, shoot
dry weight and ratio of root to shoot were recorded to be the
highest on 19 February, whereas, on 11 March these parameters
were recorded to be the lowest values.

Pod length
The length of pods also significantly influenced the seedling
growth (Table 4). All the growth parameters were significantly
better when the seeds were extracted from the medium length
pods (10–20 cm) than the other two categories of pod length (>
10 and < 20 cm).

Pre- sowing treatments
Pre-sowing treatments had significant effect on initial seedling
growth of A. lebbeck over the control (Table 5). Overall exposure
of thiourea to the seeds proved to be the best pre-sowing treat-
ment for the seedling growth as all the growth parameters are
significantly better than those of other pre-sowing treatments.


Discussion

Significant influence of collection dates on seed germination
rates was also reported by Bhardwaj et al. (2002 a & b) for A.
lebbeck. This clearly indicated that the pods collected on 19 Feb-
ruary were physiologically mature and viable enough to enable
seed germination but germination rates were decreased signifi-
cantly for the seeds collected after 19 February. This can be at-
tributed to viability loss of these seeds (Table 6). Further, mois-
ture content of these seeds also was decreased gradually from
25.43% to 19.56% (Table 6). This decrease in moisture content
might have reduced the viability of the seeds. Similar observa-
tion was also reported in A. lebbeck by Bhardwaj et al. (2002a).
Journal of Forestry Research (2010) 21(3): 338−342

341
Although the seeds of A. lebbeck are orthodox in nature but seed
germination rate decreased as its moisture content reduced.
Walters and Towill (2004) reported variation in the ability of
orthodox seeds to withstand drying and storage. Some seeds are
intermediate in their storage capability while others are fully
orthodox. This explains that in spite of A. lebbeck seeds being
orthodox, its germination rate was decreased as moisture content
reduced.

Table 4. Effect of pod length and date of collection on seedling growth of Albizia lebbeck
Date of collection
Root length
(cm)
Root dia.
(mm)
Root dry weight
(g)
Shoot length
(cm)
Shoot dia.
(mm)
Shoot dry weight
(g)
Root/shoot
ratio
9 February 19.10 7.78 3.14 58.66 5.98 11.85 0.26
19 February 24.93 8.63 3.79 74.86 6.90 13.88 0.31
1 March 22.78 7.96 3.75 67.98 6.11 12.06 0.31
11th March 17.23 7.27 2.59 55.81 5.36 10.96 0.21
C D (p = 0 .05) 0.40 0.19 0.20 1.06 0.097 1.03 0.055
Pod length (cm) Root length
(cm)
Root dia.
(mm)
Root dry weight
(g)
Shoot length
(cm)
Shoot dia.
(mm)
Shoot dry weight
(g)
Root/shoot
ratio
< 10 20.01 7.19 2.54 63.01 5.31 9.46 0.24
10−20 21.82 8.40 4.09 66.36 6.53 13.99 0.30
> 20 21.20 8.16 3.33 63.62 6.42 13.11 0.29
C D (p = 0.05) 0.34 0.16 0.17 0.92 0.084 0.89 0.048

Table 5. Effect of date of collection and pre-sowing treatments on seedling growth of Albizia lebbeck
Date of collection
Root length
(cm)
Root dia.
(mm)
Root dry weight
(g)
Shoot length
(cm)
Shoot dia.
(mm)
Shoot dry weight
(g)
Root/shoot
ratio
9 February 18.08 5.65 2.43 49.16 4.15 9.87 0.18
19 February 26.56 8.10 4.05 76.21 6.19 14.86 0.27
1 March 26.43 8.04 3.85 75.82 6.10 14.72 0.26
11 March 24.83 7.38 3.71 72.59 5.57 13.93 0.24
C D (p = 0.05) 0.36 0.011 0.52 0.18 0.013 0.52 0.002
Pre sowing treatments Root length
(cm)
Root dia.
(mm)
Root dry weight
(g)
Shoot length
(cm)
Shoot dia.
(mm)
Shoot dry weight
(g)
Root/shoot
ratio
T1 25.40 8.33 4.12 72.31 6.33 15.50 0.26
T2 25.01 7.58 3.65 71.28 5.64 13.30 0.27
T3 23.12 6.10 3.48 66.20 4.43 12.46 0.27
T4 18.14 4.82 3.09 54.21 3.51 10.37 0.22
T5 19.43 5.80 3.03 56.46 4.39 10.58 0.21
T6 19.24 5.80 2.84 56.09 4.56 9.51 0.22
T7 27.21 8.50 3.89 76.57 6.36 15.57 0.25
T8 26.92 8.78 3.79 75.56 6.59 14.84 0.26
T9 26.64 8.33 3.54 75.10 6.35 14.78 0.25
T10 26.14 8.17 3.34 74.41 6.34 14.39 0.24
T11 25.97 8.19 3.33 73.76 6.23 13.93 0.24
T12 26.44 8.06 3.08 73.61 6.15 14.42 0.22
T13 21.92 6.32 3.93 64.25 4.65 13.84 0.18
C D (p = 0.05) 0.65 0.020 0.94 0.40 0.023 0.93 0.003

The pods of 10–20 cm length also gave higher seed germina-
tion rate and better seedling growth of A. lebbeck. This is in
agreement with the report on A. lebbeck by Bal Krishna and
Singh (1995), indicating that bolder seeds extracted from longer
pods also gave better germination rate and enhanced growth of
the seedlings. Longer pods contain bolder seeds with large coty-
ledons. These seeds can store more foods or nutrients for the
developing embryo (Mutha et al. 2004). Pre-sowing treatments
deteriorated seed germination in all the treatment combinations.
Even some pre-sowing treatments completely damaged the seeds,
resulting failure of seed germination. This clearly brings out that
A. lebbeck seeds in terai zone of West Bengal do not require any
Journal of Forestry Research (2010) 21(3): 338−342

342
kind of pre-sowing treatments.

Table 6. Effect of pod length and date of collection on moisture con-
tent and viability of Albizia lebbeck seeds
Date of collection Moisture content (%) Viability (%)
9 February 30.13 (25.26)* 35.66 (36.45)
19 February 25.43 (18.44) 91.11 (73.31)
1 March 21.45 (13.39) 63.11 (52.65)
11 March 19.56 (11.22) 38.44 (38.30)
C D (p = 0.05) 0.27 3.35
Pod length (cm) Moisture content (%) Viability (%)
0–10 25.43 (18.86) 50.25 (45.58)
10–20 22.90 (15.41) 62.75 (54.34)
Above 20 24.09 (16.97) 58.25 (50.62)
C D (p = 0.05) 0.23 2.90
Notes: *Figures in parenthesis are ARC SIN values.

The seeds sown on 19 February resulted in better seedling
growth. All the growth parameters were significantly better when
the seeds were extracted from the 10−20 cm long pods. Similar
result was also reported on all parameters of seedling growth by
Shukla et al. (2007) in A. procera. The seeds collected from 19
February also had the best germination rate. This resulted into
better establishment of seedling and hence having the best
growth of seedling. Although, thiourea did not influenced seed
germination but enhanced seedling growth because it is a growth
hormone that increases the biomass (Malik 2002).


Conclusions

It was concluded from the present study that the best date of pod
collection for A. lebbeck in terai zone of west Bengal is on 19th
February but the collected pods should be more than 10 cm in
length and must be sown immediately after the collection to get
better seed germination rate. However, thiourea can be sprayed
as growth hormone in low concentration of 100 μL·L-1 for induc-
tion of better growth of the seedlings in the nursery.


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