Indian J. Plant Phy:siol.• Vol. XXVI, No.2, pp. 182-188 (June 1983)
SEED GERMINATION AND SEEDLING GROWTH RESPONSES OF SOME RICE CULTIVARS TO WATER POTENTIAL TREATMENTS K. P. SINGH l AND K. SINGH'
Department of Botany
D. A. V. College. Muzaffarnagar-251 001
(Received: October 31. 1981: Revised: January 15. 1983)
SUMMARY
Seeds of rice (OryZa :sativa L.) cultivars IR-28. Jaya, T-23. and IR-8 were subjected to water stress in terms of various external water potentials during seed germination and early seedling growth under osmoticum solution of polyethylene glycol. The cumulative germination percentage and water uptake by germinating seeds declined progressively in response to decreasing external water potentials.
However. the retardation of shoot and root lengths was significant only in response to treatments with moisture stresses of higher order (-10 bars).
It was concluded that none of the cultivars proved to be resistant to moisture stress under laboratory conditions with respect to seed germination, water uptake and early seedling growth. INTRODUCTION
Crop performance and yield are the results of genotypic expression as
modulated by continuous interactions with the environment and among the
environmental factors. Water is most widely operative limiting factor for crop
production (Hsiao et al., 1916). A better understanding of the long term in­
ffuences of water stress on growth processes would aid, therefore, in
improving agricultural practices, especiany under arid and semi-arid conditions
(Evenari et al., 1916). A good number of reviews have been published on the res­
ponses of plants to environmental stresses during recent past (Slatyer, 1913; Alvin
and Kozlowski. 1911; Koller and Hadas. 1982).
Among plant growth processes, seed germination and early seedling
growth were considered critical for raising a successful agricultural crop, as in­
directly they determine the crop stand density and consequently the yield of the
resultant crop (Gelmond, 1918). Literature on seed germination behaviour of cer­
tain crop plants under moisture stress was comprehensively available (Kaufmann,
1969; Asana, 1915; Hadas, 1916; Hagerty, 1911b; Bewley and Black, 1918).
However, no systematic work seems to have been done on seed germination and
Present Address:
'Division of Plant Physiology, Indian Agricultural Research Institute. New Delhi­
110012.
•Agricultural Research Station, Sriganganagar-335 001.
•
RICB SEBDLING RESPONSBS TO WATER POTENTIALS
183
seedling· growth under water stress of some rice cultivars which were otherwise
suitable for cultivation under Indian agroclimatic conditions. This was evident
from various reviews on physiological aspects of rice (Asana. and Sarin, 1969;
Asana, 1975; Yoshida, 1977). Based on the work done earlier (Singh and Singh.
1981a, b), it was considered of interest to study seed germination, water uptake
and early seedling growth in four cultivars of rice exposed to different water
potentials.
MATERIALS AND METHODS
The studies were conducted with four cultivars OR-28, Jaya, T-23 and
IR-8) of rice (Oryza sativa L.) during May-June, 1981. Seeds were placed on
filter paper in glass petri-dishes and treated with solutions of different external
water potentials following the method described earlier (Singh and Singh, 1981 b).
Seed germination and water uptake pattern were investigated by the method em­
ployed for earlier studies (Singh and Singh, 1981a, b, c; Singh and Singh,
1982a, b).
However, the shoot and root rengths of seedlings were studied by introdu­
cing little modifications. Bulk seeds were water-soaked for 24 h and uniform
seeds were randomly selected and placed on moistuned filter papers in large petri­
dishes. Each petri-dish was having 100 seeds and for each treatment (water po­
tential) five such petri-dishes were maintained. Five seedlings wer!) randomly
selected from each petri-dish at 4th, 6th, 8th, 10th and 12th day and shoot and root
lengths were immediately measured. Data obtained in all these twicely repeated
experiments were analysed by the method described by Chandel (1978).
RESULTS AND DISCUSSION
.
The peak of seed germination percentage in seeds treated with distilled water
(0.0 bar external water potentiar-control) was observed on 9th day after the start
of the experiment and sl1bsequently there was no significant change in seed germi­
nation percentage beyond this date of observation. Cultivar T-23 had shown
maximum germination (98.2%) and Jaya minimum (82.6%) when seeds were not
subjected to moisture stress during germination. However, IR-28, T':23 and IR-8
did not differ significantly. The T-50 of seed germination could be achieved on
3rd day, in IR-28 and T-23 and on 5th day, in Jaya and IR-8 in response to 0.0
bars external water potential treatment (Fig. 1).
The lower moisture stress (-3.0 bars external water potential) could re­
duce the seed germination percentage only marginally in IR-28. However, the
cumulative germination percentage of seeds was significantly decreased in response
Jo treatments with osmoticum solutions of (-3.0 to -10.0 bars) in Jaya,
T-23 and IR-8. On an average, the increasing moisture stress stimulated a re­
duction in seed germination percentage progressively.
Cultivar T-23 proved
to be most responsive of higher moisture stress (-7.5 and -10.0 bars external
184 SINGH AND SINGH
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Fig. 1. A. B. C & O-Ogival series showing germination percentages of seeds of rice varieties ,IR-2e,
Jaya. T-23 and IR-S) under different external water potentials.
•
r
I
RICE SEIIDLlNG RESPONSES TO WATER POTENTIALS
•
.. 185
water potentials) with reference to reduction in seed germination. The seed ger­
mination of IR-28 was least affected by -7.5 bars external water potential while
Jaya by --10.0 bars. However, Jaya and IR-8 did not differ significantly from
each other with respect to the reduction of seed germination percentage as affected
by -7.5 bars external water potential. Other two cultivars differed significantly
from each other in response to this treatment. IR-8 and IR-28 have shown ra­
markabfe similarity and did not differ significantly, while the other two cultivars
differed significantly from each other in relation to their responses to highest mois­
ture stress (Fig. 1).
The decline in seed germination percentage under conditions of increasing
moistUre stress was also reported by Hadas and Stibbe (1973) in Cicer arietinum L
and by Hadas (1976) in Vicia laba L. Following a similar experimental approach,
there has been report on reduction of seed germination percentage in response to
alterabfe external water potentials in osmoticum solutions (Singh and Singh, 1981 a,
b, c, 1982a, b; Singh, 1983).
Although, a progressive fall in water uptake potentiality (as determined on
seed dry weight basis at six hourly intervals) of germinating seeds under conditions
of increasing moisture stress was observed, -3.0 bars external potential could im­
pose only an insignificant constraint on water uptake in af( the four cultiv8f8.
Water uptake capacity by germinating seeds was significantly lowered by moisture
stresses of the higher order (-7.5 and -10.0 bars) in all the four cultivars uooer
investigation (Fig. 2).
The peak of water uptake by germinating seeds was noticed at 36 h in IR-28,
Jaya and IR-8 and at 42 h in T-23 under control condition (0.0 external water
potential). After these peak periods (water uptake equilibria), there was no further
remarkable change in water uptake upto 48 h beyond which observations were not
recorded. It was interesting to observe that these cultivars proved to be similar
in relation to the loss of water uptake (at their respective peaks of water uptake)
in response to the lowest external water potential (-10.0 bars) treatment as evi­
denced by insignificant intervarietal differences between the reduction of water up­
take potentialities over their respective controls (Fig. 2).
An analysis of data obtained on the effect of moisture stress on early seedli~
growth had revealed that there was no effect of decreasing external water poten­
tial on seedling growth in terms of shoot and root length. It was further observed
that -3.0 to -7.5 bars external water potential treatments had stimulated only
insignificant reduction of shoot as well as root lengths in 4 to 8 days old seedlings
in IR-28, Jaya and T-23 of rice. Shoot lengths of all the tested cultivars were
significantly lowered by higher moisture stress (-10.0 bars} especially in case of
10 and 12 days old seedlings. Root lengths of 8, 10 and 12 days Qld seedlings
were also significantly reduced by -10.0 bars external water potential treatment
in IR-28, T-23 and IR-8 but Jaya seems to be an exception where even the mois­
186
SINGH AND SINGH
I R 28
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Fig. 2.
POTENTIALS (BA~Sl TREATMENTS
A. B, C ft O-The water uptake {%d.w.=% of seeds dry weight basis} patterns by germinat­
ing seeds of four rice varieties under different external water potentials in osmoticum
solutions.
ture stress of highest order could not stimulate a significant root length retardation
of seedlings of any age (Table O.
IR-8 appears to be relatively more sensitive to seedling growth inhibitory
action of increasing moisture stress because in this cultivar the reduction of shoot
and root lengths was significant in response to external water potential treatments
(--5 to -10 bars). With reference to the reduction of shoot length by highest mois­
ture stress (-10.0 bars), T-23 proved to be comparatively most responsive. Jaya and
IR-28 were more or less similar with this point of view. Other cultivars differed
significantly from each other with respect to their shoot growth response to higher
moisture stress. IR-8 was significantly different from other three cultivars. A dec­
line in seedling growth in response to increasing moistUre stress under field as
well as laboratory conditions was also reported by earlier workers (lawlor, 1969;
Singh and Singh, 1981 a. b). This has been confirmed by our previous experiments
(Singh and Singh, 1981a, b) and it may now be concluded that use of polyethy­
lene glycol '6000 (PEG) is preferable over manitol. It was further observed that
the moisture stress lower than ~ 3.0 bars external water potentials were remark­
ably repressive for seed germination process as was also earlier reported by Hagerty
(1977b). The peak (equilibrium) of water uptake was achieved at 36 h (at 42 h
in T-23) and these peak hours were observed to be constant for all the tested ex·
ternal water potentials.
It may be concluded that none of the cultivars under study proved to be
satisfactorily resistant to moisture stress in seed germination and water.. uptake
potentialjty, though IR-28, Jaya and T-23 proved to be relatively lessersusceptibfe
than IR-S.
.
.
•
0.20*
0.61
0.86
2.01
3.60
0.18*
0.25
0.33
0.81
1.07
0.23*
0.75*
0.99*
2.13
3.71
0.21*
0.30*
0.39*
0.89*
1.15
0.24
0.81
1.15
2.46
3.93
0.19
0.36
0.44
0.95
1.27
4
6
8
10
12
T-23
IR-8.
LSD between varietal means (Shoot) length=0.25
(Root)
==0.34
LSD between
"
"
Each figure is secondilly average o.f 5.
*lnsignificdt1t at 51Mllevei of significance.
0.31*
0.33*
0.56*
0.82*
0.90
0.25*
0.35*
0.70*
0.91*
1.08*
0.31*
0.36*
0.61*
0.84*
1.04*
0.25*
0.38*
0.74
1.00
1.72
0.32
0.40
0.66
0.89.
1.11
0.26
0.41
0.79
1.25
1.96
4
6
8
10
12
Jaya
1.66*
2.60*
2.92*
4.55*
5.20*
0.45*
0.80*
0.96·
1.65*
2.46*
1.64*
2.68*
3.09*
4.66*
5.28*
0.47*
0.84*
1.01*
1.79*
2.52*
1.64
2.74
3.19
4.82
5.35
0.46
0.88
1.22
1.85
2.67
4
6
8
10
12
IR-28
1.83*
2.87*
4.25*
5.85*
8.43*
0.64*
1.11*
1.60*
2.25
3.16
1.80*
3.09*
4.41*
6.07*
8.61*
0.65*
1.32*
1.64*
2.31*
3.48*
1.82
3.14
4.59
6.12
8.77
Root
Shoot
-5.0 bars
Root
Shoot
Root
-3.0 bars
Shoot
0.0 bar
(Control)
063
1.45
1.71
2.70
3.60
Seed­
ling
age
(days)
0.30*
0.29*
0.50*
0.74*
0.88
0.13*
0.52
0.81
1.97
3.47
0.19*
0.21
0.30
0.76
0.90'
1.64*
2.59*
2.87*
4.41*
5.14*
1.81*
2.76*
4.13*
5.61*
8.21
Root
0.26*
0.36*
0.68*
0.85*
0.64*
0.43*
0.77*
0.91*
1.58*
2.37*
0.60*
1.09*
1.55*
2.09
3.00
Shoot
-7.6 bars
0.17*
0.18
0.27
0.70
0.81
0.27*
0.32*
0.61
0.77
0.80
0.44*
0.76*
0.85*
1.43
2.24
0.62*
0.93*
1.24
1.86
2.75
Shoot
0.11*
0.40
0.74
1.84
3.31
0.22*
0.27*
0.43
0.69
0.75
1.62*
2.54*
2.71*
4.38*
5.0'*
1.80*
2.54*
4.00
5.50
8.19
Root
-10.0 bars
Average shoot and root lengths (em) under different external water potentials (bars)
4
6
8
10
12
Variety LSD (Shoot)
==0.11
LSD (Root)
-0.19
LSD (Shoot)
=0.170
LSD (Root)
=0.23
LSD (Shoot)
=0.37
LSD (Root)
=0.e1
LSD (shoot)
-0.43
LSD (Root)
=0.56
LSD at 5%
level of
significance
TABLE I. Average shoot and root lengths of seedlings of four (lR-28, Jaya, T-23 and IR-8) varieties of rice under
different external water potentials
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188
SI!i(GQ AND SINGH
';.­
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