Standardization of Dormancy Induction Treatments in Groundnut cv. TMV 7
M. Ameer Junaithal Begum
Effect of different growth retardants viz., MH at 5000, 10000, 15000 ppm, ccc
at 1000, 2000, 3000 ppm and ABA at 250 and 500 ppm on inducing dormancy in non-dormant
groundnut cv. TMV 7 was studied by foliar application at 70 and 80 days after
sowing. It was evident from the results that ABA 500 ppm applied at 70 days
after sowing was most effective in inducing dormancy in the resultant seeds
as well as recorded the lowest in situ germination of pods.
Received: September 12, 2013;
Accepted: October 29, 2013;
Published: February 27, 2014
Dormancy is the natural evolutionary consequence, however, depending on the
situation dormancy may be a boon or evil in groundnut. In general, in groundnut
bunch types are non-dormant while spreading and semi spreading types are having
a varied period of dormancy.
The groundnut crop by its very nature of fruiting underground cannot be harvested
without sufficient moisture in the soil. Rain at the time of harvest are often
either too low resulting in imperfect harvest at increased cost or excessive
when harvesting has to be delayed till the fields come to a workable condition.
In the latter circumstances, considerable loss by the sprouting of the seed
occurs in the bunch varieties. The fully germinated seed is quite useless while
the partially sprouted one is of poor quality with low oil content and has a
tendency for rapid deterioration. Specially in black soil regions, the higher
percentage of sprouting of pods is commonly noticed due to high moisture retention
capacity of the soil. About 20% loss in bunch groundnut pod yields has been
reported due to in situ germination (Nagarjun and
Radder, 1983). Eighty percent of groundnut seeds had germinated in the field
due to heavy rain (John et al., 1948) and 20-50%
pods germinate due to rains at pod maturity stage. Therefore, the non-dormant
nature of seed in bunch groundnut is considered to be the major problem in its
cultivation. To overcome this kind of situation, in most of the bunch groundnut
growing areas, there is an important need to search for a method of inducing
seed dormancy to save the produce and to retain the seed quality against field
MATERIALS AND METHODS
To induce dormancy in non-dormant cv. TMV 7, the plants were raised in pots
and were sprayed with different growth retardants at 70 and 80 days after sowing
in addition to control which was not sprayed with growth retardants.
||Maleic hydrazide (MH) 5000 ppm
||Maleic hydrazide (MH) 10000 ppm
||Maleic hydrazide (MH) 15000 ppm
||Cycocel (CCC) 1000 ppm
||Cycocel (CCC) 2000 ppm
||Cycocel (CCC) 3000 ppm
||Abscisic acid (ABA) 250 ppm
||Abscisic acid (ABA) 500 ppm
Stages of application
||70 days after sowing
||80 days after sowing
The experiment was conducted as factorial completely randomized design at the
Department of Seed Science and Technology, Tamil Nadu Agricultural University,
Coimbatore. After the attainment of maturity, the plants were left in pots for
20 days with regular watering for germination of pods in situ. After
20 days, the pods were lifted and the number of pods sprouted in each treatment
were counted. Germination test was conducted in sand medium using 4x100 seeds
and germination percent of resultant seeds were taken at 10th day.
RESULTS AND DISCUSSION
In groundnut, bunch type cultivars lack seed dormancy which cause considerable
loss due to sprouting of pods in the field. The loss due to this pre-harvest
sprouting is nearly 20-40% depending upon the variety as reported by John
et al. (1948). To overcome this kind of loss, the present experiment
was conducted to find out a suitable method for inducing seed dormancy so as
to save the produce from sprouting in the field. To induce the dormancy, the
crop of non-dormant groundnut cultivar TMV 7 was sprayed with Maleic Hydrazide
(MH), Cycocel (CCC) and Abscisic Acid (ABA) at different concentrations in different
days viz., 70 and 80 days after sowing. From the results, it is evident that
dormancy was induced in groundnut cv. TMV 7 by spraying of ABA 500 ppm on 70
days after sowing, MH 15000 ppm on 70 days after sowing and CCC 3000 ppm on
80 days after sowing. The above treatments recorded the lowest in situ germination
of 2% while unsprayed control recorded the maximum of 44% (Table
1). ABA 500 ppm applied at 70 days after sowing registered superiority over
other treatments in inducing dormancy of resultant kernels to the extent of
81% over control while the resultant kernels of control plants recorded 93%
germination (Fig. 1).
The result of the present study was evinced by Ketring
(1973) and Narasimha Narasimhareddy and Swamy (1976)
by expressing the inhibitory action of ABA on germination of groundnut seed.
Sengupta et al. (1979) observed the inhibition
of groundnut seed germination by ABA and CCC but the extent of inhibition was
more due to ABA than CCC. The inhibitory effect imposed by ABA was reversed
by kinetin application and they concluded that ABA and kinetin control the seed
dormancy and germination in groundnut, respectively. ABA is a naturally occuring
organic substance that inhibit seed germination (Ketring,
1973). Veldstra (1945) proposed that the inhibition
of germination would result from changes in membrane permeability.
|| Effect growth retardants on germination (%) of resultant
seeds of groundunt cv. TMV 7
|| Effect of foliar application of growth retardants on in
situ germination (%) of groundnut cultivar TMV 7
|Figures in parenthesis indicate arcsine values
ABA inhibited groundnut seed germination and the factor which appeared limiting
in the presence of ABA was low level of ethylene production by the seed. Thus,
ABA may prevent germination and cause dormancy by preventing ethylene synthesis
(Ketring and Morgan, 1971). ABA is an auxin antagonist
and the mode of action of this auxin antogonisms have been shown to be non competitive.
The suggested mechanisms of action for the observed inhibition of growth are:
Combination of IAA with a protein and competition at a particular site by the
structurally similar trans-cinnamic acid; formation of loose combination or
easily dissociated coumarin compounds of enzymes or plant cell metabolites;
reactions with sulf hydryl groups of enzymes by the unsaturated lactones, coumarin
and protoanemonin. Thus, the machanism of action of the inhibitors in preventing
growth and germination was at the molecular level (Ketring,
1973). The stimulation of plant growth and seed germination by GA is counteracted
or inhibited by ABA. Haber et al. (1969) have
shown that the promotion of germination by GA was due to the expansion of existing
cells and this expansion was inhibited by ABA. Chen and
Osborne (1970) stated that GA activates preformed mRNA stored in the embryo
and ABA blocks the existing messages but perhaps at sites different from those
of GA. GA did not stimulate DNA synthesis but ABA inhibited it once it was initiated.
The inhibition of expression of ot-amylase genes by ABA had been reported by
Pagano et al. (1997) in barley. Le
Page-Degivry et al. (1990) observed that the dormancy of Helianthus
annus appeared to be dependent on ABA synthesis but not concomitant with
its accumulation. Seshu and Dadlani (1991) reported
that seed dormancy in rice is a result of accumulation of ABA in the hull and
pericarp during maturation which strongly inhibits amylase activity in the germinating
seeds. ABA inhibit cell division and cell elongation and this could occur by
breaking synthesis of a particular RNA molecule (Ketring,
The inhibitory effect of CCC on germination of groundnut seed in the present
study is in continuity with Ketring (1973) and they
reported that CCC is a synthetic growth retardant which inhibits seed germination.
In the presence of CCC, diffusible auxin from pea plant apices was reduced.
CCC prevents synthesis of a GA like substances in non-dormant embryo of wild
oats, wheat, barley. Inhibition of groundnut seed germination by CCC was reported
earlier by Sengupta et al. (1979) which was in
confirmation with the present study. The induction of seed dormancy in groundnut
by MH in the present investigation was in confirmity with Gupta
et al. (1985). Nagarajan and Gopalakrishnan (1958) reported that
the presence of auxin like substances in the groundnut seed is responsible for
germination and making it non-dormant. The introduction of antiauxins to the
seed by means of foliar application at the time of kernel development may suppress
the auxin formation and induce dormancy. Maleic hydrazide (diethanolamine salt
of 1,2-dihydroxy-3,6-pyridazinedione) a growth and respiratory inhibitor, possesses
the characteristics of an anti-auxin, has been found to be capable of inducing
dormancy by antagonizing with auxin in groundnut. Since MH is an auxin-antagonist,
the primary effect of MH on inducing dormancy seems to be through interference
in the tryptophan metabolism, as the tryptophan is the precursor in the synthesis
of auxins (Karivaratharaju and Rao, 1972). Besides
this, MH was found to increase the content of another amino acid, hydroxy proline
which inhibit the auxin induced cell elongation. Nagarjun
and Radder (1983) observed that the moisture content and catalase enzyme
activity reduced during induction of dormancy by MH. Seed germination is an
energy requiring process and is therefore dependent upon the moisture content
of the seed. In addition to this, dormancy is also related to control of enzyme
formation and inactivation of seed and they concluded that the reduction in
moisture content of seed also indicates that the application of MH prevented
the pods to absorb moisture and thereby it inhibits imbibition which is the
primary phase in seed germination.
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