Dormancy breaking studies and seed germination in Arenga wightii Griffith

Abstract

Arenga wightii Griffith, an endemic palm, of Western Ghats and south and central Sahyadris having multiple uses is currently under threat due to habitat loss and over exploitation. Since seeds are the major propagules of this palm, seed study was carried out with a view to conserve this highly promising tree, in both ex-situ and in- situ conditions. The study included seed viability, germination, desiccation and dormancy breaking tests. The results of the study suggest desiccation, GA3/ acid treatment enhance germination, and dormancy observed is of both physiological and mechanical. The cost efficient means of germination induction is desiccation which could aid the farmers and common people in cultivating the species at large extent enabling reintroduction of the species.

Full text

47
(Manuscript Received: 19.10.2022, Revised: 11.05.2023, Accepted: 20.07.2023)
*Corresponding Author:drjoemon70@gmail.com
Journal of Plantation Crops, 2023, 51(2): 47-53
Research Article
Arenga wightii Griffith, an endemic palm, of Western Ghats and south and central Sahyadris having multiple uses is currently under
threat due to habitat loss and over exploitation. Since seeds are the major propagules of this palm, seed study was carried out with a
view to conserve this highly promising tree, in both ex-situ and in- situ conditions. The study included seed viability, germination,
desiccation and dormancy breaking tests. The results of the study suggest desiccation, GA / acid treatment enhance germination, and
3
dormancy observed is of both physiological and mechanical. The cost efficient means of germination induction is desiccation which
could aid the farmers and common people in cultivating the species at large extent enabling reintroduction of the species.
Arenga wightii, (Arecaceae) commonly
known as Wight's Sago Palm or Wild Coconut is a
solitary monoecious palm of India, frequently
found distributed in the evergreen forests of
Western Ghats and south and central Sahyadris at an
elevation of 300-1000m,where moisture content
and humus are abundant (Renuka et al, 1996). The
palm is pleonanthic as it starts flowering after 5-10
years of planting and perishes after producing a
series of inflorescences. Male and female spadices
are found distinct. At present due to habitat
destruction and anthropogenic activities the
population of the species is diminishing in its
natural habitats and is categorized as vulnerable in
IUCN Red List of Threatened plants (Johnson,
1998). The palm has medicinal properties and is
widely used in folk medicine by the ethnic groups of
Kerala and Tamil Nadu as a source of food,
medicine and building material. Rajasekharan et
al, (1990), reported that Kani tribe of Kerala has a
custom of using fresh toddy from the peduncle of
Arenga wightii internally for the treatment of
Jaundice. Renuka, (1999), in her book “Palms of
Kerala” stated that the starch from the trunk of
Arenga wightii has medicinal properties and is used
in the treatment of body rashes. Asha et al,( 2002),
described that Paniyan and Kani tribes of
Malappuram and Wayanad districts of Kerala
Dormancy breaking studies and seed germination in Arenga wightii
Griffith
KSCSTE- Jawaharlal Nehru Tropical Botanic Garden & Research Institute, Palode – 695562,
Thiruvananthapuram, Kerala, India.
Abstract
Joemon Jacob*, C. R. Chitra and C. Anilkumar
Introduction
doi: 10.25081/jpc.2023.v51.i2.8665
Keywords: Arenga wightii, Desiccation, Dormancy, Seed germination, Storage, Viability

consume fresh toddy from the young inflorescence
and juice of fruit husk as a cure for Jaundice. While
documenting the wild edibles consumed by paniya
tribe of Kerala, Narayanan et al, (2003), recorded
that the tribe used the pith of Arenga wightii against
venereal diseases. Sasidharan et al, (2006) stated
that Malampandaram tribe of Periyar Tiger Reserve
use the stem pith of Arenga wightii as a remedy for
Jaundice. Similarly, Augustine et al, (2010),
documented that Malampandaram tribe of Periyar
Tiger Reserve, Western Ghats has a practice of
serving little quantity of fresh toddy from the
inflorescence of Arenga wightii, hardened with the
roots of Thottea siliquosa to pregnant women to
prevent abnormal child birth. This palm is also used
for making brooms, palm wine and is a unique
source of starch.
Materials and methods
Mature and ripened fruits were hand harvested
from the natural population at Ponmudi as
well a s from t h e Pa l matu m of JNT B G R I,
Thiruvananthapuram during the hot and humid
Fruit/ Seed collection
Moisture content determination
Seed mois ture content was determine d
through high constant hot air oven method (ISTA,
2008). Seeds were surface dried on blotting paper at
laboratory conditions (28 ± 2°C, 70% RH). For dry
weight determination, the samples were taken in a
pre-weighed bottle and weighed in an electronic
0
balance, then dried in a hot air oven at 130 C for 1
hour or until the weight became constant. For each
test, 5 replicates of samples were used. Dry weight
of each sample of each test was recorded after
cooling to room temperature in a desiccator.
Moisture content was determined by the following
formula and was expressed as percentage.
Seeds kept open in laboratory conditions served as control.
Germination test
Thirty seeds in three replicates were tested for
germination. Germination test was conducted in
wet rolled, acid-free, germination paper towels
pla c e d in a seed germinator without l i g ht
0
maintained at 30 ± 2 C/80% RH.
Seed viability tests
Seed viability was determined by conducting
germination test as well as supporting viability
tests. Both destructive (tetrazolium Test) and non-
destructive methods (conductivity Test) were
carried out.
Tetrazolium test (Moore, 1985)
Seeds were at first pre-soaked in sterile
distilled water for 2 hours at room temperature
Moisture content (%) = Fresh weight- Dry weight
Fresh weight × 100
48
Dormancy studies in Arenga palm
A. Habit, B. Male inflorescence, C. Infrutescence, D. Tricarpellary
fruits, E. Seeds, F. Tetrazolium test, G. Seed germination
months of April-May in two consecutive years,
2017 and 2018. The fruits were sorted, so that
infected and mechanically damaged fruits were
discarded. Seeds were extracted from fruits by
depulping and washed in water to extract the
im miscible seeds. Purity of the s eeds was
determined on the basis of pure seed number / water
floating method. Morphological characters of fruits
an d s eed s w ere do cum en t ed al on g wi th
photographs. Seeds were provided accession
number and few seeds were curated as active and
reference collection of JNTBGRI seed bank.

Desiccation
Seeds of one lot were desiccated to different
moisture contents until lowest moisture content
having substantial seed viability was attained.
Seeds were subjected to both slow and fast
desiccation. Slow desiccation was attained with
seeds kept opened at laboratory conditions (28 ±
0
2 C/70% RH). For fast desiccation about 100 seeds,
tied in muslin cloth bags, in four replicates, were
placed over freshly regenerated silica gel in a
desiccator for different intervals. The silica gel in
the desiccator was changed after every 24 hours. In
both the conditions moisture content of the seeds
were recorded at regular intervals. Germination
tests were also done at each moisture content levels.
Desiccated seeds were conditioned at 80% RH for
every 24 hours prior to germination test to avoid
imbibitional injury (Ellis et al., 1990). Germination
data were recorded consequently.
Dormancy breaking treatments
The following pre-treatments were carried out
for breaking the dormancy. All treatments were
carried out in fresh seeds with 39 ± 1.32 % moisture
content.
(a).GA treatment: -Seeds were pre-treated
3
Speed of germination= n1/d1+n2/d2+n3/d3+----------
Results and Discussion
Fruit is a globose – sub globose greenish black
berry, tricarpellary syncarpus and sessile. Each fruit
with three persistent green, small, triangular and
Moisture
content %
Germination
%
Tetrazolium Test
Conductivity
test
39 ± 1.32
20 ± 0.9
Embryo, endosperm
and cotyledons not
stained
8.35 ± 0.16µs
35 ± 1.4
70 ± 0.7
Embryo deeply stained,
endosperm and
cotyledons stained red
5.13 ± 0.02 µs
30.2 ± 0.96
68 ± 1.4
Embryo, endosperm
and cotyledons stained
red
5.67 ± 0.05 µs
27.4 ± 0.93
65 ± 1
Embryo, endosperm
and cotyledons stained
red
6.16 ± 0.09 µs
24 ± 1.7
60 ± 1.2
Embryo, endosperm
and cotyledons stained
feebly
6.49 ± 0.07 µs
22.4 ± 0.87
48 ± 0.5
Very slight colour
change, embryo turned
slight red
7.36 ± 0.3 µs
17 ± 0.71
Nil
No colour change
8.79 ± 0.5 µs
Table 1. Seed viability tests
Data Mean ±SD
Where, n = number of germinated seeds, d= number of days.
Joemon Jacob et al.
0
conditions (28 ± 2 C/70% RH). Three replicates of
10 seeds each were used for a treatment. After
pre-cond i t ioni n g , t h e s eeds were b i s ecte d
longitudinally without damaging and exposing the
embryo, and immersed in1% tetrazolium solution
for 24 hours. The tetrazolium solution, after
incubation, was decanted and seeds were rinsed
thoroughly with water. The staining pattern of
embryo, endosperm and cotyledon were noted.
with GA solution of different concentrations (0, 50,
3
100, 250, 500, 1000, 2000, 3000, 4000 and 5000
ppm). For this 30 numbers of seeds in triplicates
were immersed in GA solutions of respective
3
concentrations for 24 hours and after that seeds
were tested for germination. Seeds immersed in
distilled water for 24 hours served as control.
(b). GA treatments were carried out in
3
operculum removed seeds and also in scarified
seeds.
(c). Acid scarification: - Seeds were pre-
treated with concentrated Sulphuric Acid for
different time durations (1, 3, 5, 7, 10, 12 and 15
minutes),followed by seeds washed in running tap
water for 24 hours and tested for germination.
(d). Hot water treatment: - Seeds were pre-
0
treated with 70 C hot water for different durations
(1, 3, 5, 7, 10 minutes) and tested for germination.
Speed of germination was calculated using the
following formula (Czabator, 1962).
Conductivity test
Three replicates of 10 each fresh as well as
desiccated seeds were soaked in 50ml distilled
water in a beaker. The beaker was covered to
minimize evaporation and contamination by dust
and was kept in open laboratory conditions (28 ±
0
2 C/70% RH) for 24 hours. The leachate was
collected after 24 hours soaking and conductivity
test was performed using Systronics Conductivity
meter (306) ( Vieira et a l , 2 0 0 1 ) . Specific
- -
conductance was expressed in µs cm 1g 1.
49

valvate petals and three greenish yellow triangular
acrescent sepals enclose 2-3 seeds having
dimension [ 2.41 ± 1.1 x 2. 22 ±0.9 cm (LxB)] and
weight (20.37 ± 0.7 g). Seeds are blackish brown,
compressed or planoconvex, longitudinally striated
with triangular apex and base. Seed coat is hard and
embryo is lateral. Seeds have 2.12 ± 0.5 x 1.47 ±
1.3cm (LxB) dimension, 0.95 ± 0.5 cm thickness,
and 2.31 ± 0.5gm weights.
Initial moisture content of the seeds was 39 ±
1.32 %. Fresh seeds registered only 20 ± 1.3 %
germination, that too after an incubation period of
11 months. Seeds have dormancy, which has to
undergo dormancy breaking treatments.
Among the two types of germination in palms
(remote and adjacent), in Arenga wightii adjacent
type of germination was observed. A small portion
of the cotyledon emerges from the seed which
appears as a swollen body abutting the seed surface
and is called 'button'. The first seedling root or
radicle is usually narrow and very short lived and is
quickly replaced by roots formed at the seedling
stem base (adventitious roots), the haustorium
remains inside the seed absorbing food from the
endosperm. However, in remote type germination,
the cotyledonary petiole close to the seedling root
emerges early from the seed. The cotyledonary
petiole grows downwards into the soil and swells at
its base from which radicle and plumule emerges.
The actual cotyledon or seed leaf remains inside the
seed which is haustorium and it transfers nutrients
from the endosperm to the young seedlings. Here
radicle persists for some time and produces lateral
roots
Viability is one of the most important aspects
of seed quality because it is crucial that seeds
conserved in a gene bank can develop in to normal
plants for future use. In tetrazolium test, seeds with
35 ± 1.4% moisture content exhibited high
germination % (70 ± 0.7) maximum staining
intensity and low conductivity value. Staining
intensity was found to decrease with the reduction
of germination %, while conductivity value
increases with the reduction of germination %
(Table – 1). This is in conformity with the fact that
seed viability is directly proportional to staining
Fig. 1. Effect of slow desiccation on seed viability
Fig. 2. Effect of slow desiccation on seed viability
Fig. 3. Effect of GA treatment on seed viability
3
Fig. 4. Effect of acid treatment on seed viability
50
Dormancy studies in Arenga palm

Fig. 6. Effect of scarification on seed viability
intensity and inversely proportional to conductivity
values. Fresh seeds of Arenga wightii have low
germination %, very low staining intensity and high
conductivity value. Similar results of tetrazolium
test were reported in Jatropha curcas seeds (Kak et
al, 2009) and also in Baliospermum montanum
seeds (Gupta et al, 2010). Simon and Raja-Harun
(1972) and Halloin (1975) carried out conductivity
test in the seeds of Pisum sativum and Gossypium
hirsutum, respectively and observed a negative
corre l a t i o n between viability and leachate
conductivity.
When seeds are subjected to slow desiccation,
within 3 days, moisture content is reduced to 35 ±
1.4% with 70 ± 0.7% germination. Germination %
is retained up to 60 ± 1.2% with the reduction of
moisture content to 24 ± 1.7% within 10 days.
Within 25 days, moisture content is reduced to 17 ±
0.71% and seeds lost viability completely (Fig. 1).
In fast desiccation, the rate of loss of viability is
more rapid, as germination % could not be
increased considerably. Within a week moisture
content is reduced to 12 ± 0.67 with a corresponding
germination % of 40 ± 1.4 (Fig.2). This may be due
to the desiccation stress and hence it can be
inte r pr e te d that desic c at i on may enhan c e
germination process to some extent. When speed of
germination was calculated, peak values are with
seeds with higher germination % (Fig.1 and Fig.2).
Since speed of germination varies with day of
completion of germination it did not show
correlation with germination percentage.
Higher concentrat ion of GA enhanced
3
germination percentage. Pre-treatment with 8.66 mM
(3000ppm) solution enhanced germination % to 80 ±
0.7 within 95 ± 1.3 days followed by 11.55 mM
(4000ppm) solution which resulted 78 ± 0.51%
germination within 98 ± 1.4 days. Control seeds
showed only 45 ± 0.13 germination within 67 ± 0.5 %
days (figure – 3).
When fresh seeds were pre-treated with
concentrated H SO for different durations (1 to 15
2 4
minutes), seeds pre- treated for 7 minutes showed
enhanced germination percentage to 80 ± 0.7 within
58 ± 0.5 days followed by 10 minutes pre-treatment
with 73 ± 0.2% germination within 88 ± 0.6 days
(figure – 4).
Seeds when tested for germination, after
removing the operculam, showed no effect, but
seeds pre-treated with GA 2.89 mM (1000ppm)
3
solution after removing the operculam, showed
germination of 69.6 ± 1.2% within 17 ± 0.54 days.
Same seeds pre-treated with GA 1.44 mM
3
(500ppm) solution after removing the operculum
showed 58 ± 0.6% germination within 48 ± 0.4
days (figure – 5).
Scarification also did not improve germination
significantly. Scarified seeds pre-treated with GA
3
2.89 mM (1000ppm) solution recorded 65 ± 1.1%
germination within 83 ± 1.4 days. Same seeds pre-
treated with GA3 1.44 mM (500ppm) solution after
Fig. 5. Effect of removal of operculum on seed viability Fig. 7. Effect of hot water treatment on seed viability
51
Joemon Jacob et al.

scarification show 40 ± 0.7% germination within 90
± 0.6 days (figure- 6).
Hot water t r e a t m e n t had no e ff e c t on
increasing seed germination. Seeds showed a
maximum of 28 ± 1.3% germination within 49 ± 1.7
days (figure – 7). Seeds are found to decay after the
germination and germinated seeds also did not
survive.
Both the GA and acid treatments enhanced
3
germi n a ti o n percen t a ge , but mo re speed y
germination was found during acid treatment. Since
80% germination was registered within 98 ± 1.4
days in GA treatment, as against 58 ± 0.5 days in
3
acid treatment, dormancy may be both mechanical
and physiological.
GA has been established as an effective
3
dormancy breaking growth regulator in many plant
species including maize (Rood et al, 1990), in
Macaw palm (Oliveira et al, 2013), in Gentiana
rigescens seeds (Yang et al, 2011), in five species of
Cacti (Rojas- Arechiga et al, 2011) and in
Penstemon digitalis (De Mello et al, 2009).
Mechanical dormancy in palms is due to
restriction of embryo protrusion during germination
by operculum of the seeds as reported in Elaeis
guineensis (Myint et al, 2010), in Pritchardia
remota (Perez et al, 2008) and in Macaw palm
(Reberio et al, 2011). GA treatment after removing
3
the operculum was found effective in Pritchardia
remota seeds (Perez et al, 2008).
Pre-treatment with conc. H SO found to
2 4
enhance seed germination in legume seeds (Argel
and Paton, 1999), in three species of Stylosanthes
(Nan et al, 1998), in Santalum album (Nagaveni and
Srimathi, 1980) and in Koelreuteria paniculata
(Rehman and Park, 2000).
It can be concluded that the dormancy in
Arenga wightii seeds was due to the combined effect
of physiological and mechanical parameters and it
can be overcome by desiccation / GA and acid
3
treatment. The highest germination percentage was
recorded when seeds are pre-treated with GA 8.66
3
mM (3000 ppm) solution and also pre-treated with
conc. H SO for 7 minutes. Speedy germination was
2 4
found in acid treatment. When operculum removed
seeds were pre-tre ated with GA 2.8 9 mM
3
(1000ppm) solution, recorded 69.6 ± 1.2%
germination within 17 ± 0.54 days. The most cost
Acknowledgements
The authors are thankful to the Director,
JNTBGRI for all the facilities extended.
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