ASSESSING OF THE TOLERANCE OF PINUS - HALEPENSIS MILL. SEEDS TO WATER AND SALINE - OAJI
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FORESTRY IDEAS, 2019, vol. 25, No 1 (57): 160–170
ASSESSING OF THE TOLERANCE OF PINUS
HALEPENSIS MILL. SEEDS TO WATER AND SALINE
STRESS AT THE GERMINATION STAGE
Mohamed Zouidi1,2, Amine Habib Borsali1,2*, Kadda Hachem1, Ayoub Allam1,
Amel Naimi1, and Imane Hakmi1
1
University ′Dr. Moulay Tahar′, 20 000 Saïda, Algeria. *E-mail: rhizobiologie@yahoo.fr
2
Laboratory ′Water Resources and environment′, 20 000 Saïda, Algeria.
Received: 04 May 2018 Accepted: 12 June 2019
Abstract
Arid and semi-arid ecosystems cover a large part of the southern fringe countries of the Med-
iterranean basin. Drought and salinization are the major processes of steppe land degradation.
The objective of this work was to investigate the tolerance to water and saline stress of Aleppo
pine (Pinus halepensis Mill.) seeds at the germinating stage. The adopted methodology used
increasing concentrations under a controlled temperature of 20 °C for 30 germination days of
seeds. Germination responses of seeds to different degrees of salt stress caused by NaCl (1,
2, 3, 4, and 5 g·L-1) and the water stress caused by polyethylene glycol (–0.05, –0.25, –0.5, –1,
and –2 bars) under a temperature of 20 °C showed that salt and water stress have decreased
the percentage of seed germination of Aleppo pine seeds for a period of 30 days. In the control
treatment (distilled water) with no stress the seeds showed a germination rate of 89 % for salt
stress and 90 % for water stress. The results of the study showed that salt and drought have a
depressive effect on the germination rate of Aleppo pine with a tolerance of 4 g·L-1 and –1 bars
for the stresses used.
Key words: Aleppo pine, drought, germination tests, NaCl, Polyethylene glycol (PEG),
semi-arid.
Introduction ceive an annual average rainfall between
100 and 300 mm for the arid and between
Algeria is one of the most water-deficient 300 and 600 mm for the semi-arid one (Le
regions in the world, and the water re- Houerou 1995, Nedjraoui 2003, Ramade
sources are subjected to strong natural, 2003). Besides, they are characterized
climatic and anthropogenic pressures by very restrictive edapho-climatic condi-
(Bellal 2011). The water deficit is more tions, thus posing challenges to survival of
than 20 % for the western region, 13 % for some indigenous plant species, which are
the central and 12 % for the eastern part of subjected to constant stress by the severe
the country (Ould Amara 2000, Bouguerra environment.
2001). Arid and semi-arid area cover very In these regions, the availability of wa-
large surface and are characterized by a ter, salinity and some other soil character-
high rainfall irregularity. These areas re- istics are among the main factors limitingAssessing of the Tolerance of Pinus halepensis Mill. Seeds to Water and Saline ... 161
plant productivity (Zid and Grignon 1991). act in the regulation of germination (water,
In Algeria, the long-observed drought has temperature, light and salinity). Also, ger-
clearly led to the process of salinization of mination is regulated by genotypic char-
soils on 3.2 million hectares (Benmahioul acteristics (Gutterman 1994). Thus, seed
et al. 2009). This natural constraint has germination is the most sensitive stage of
had a huge impact on the stability of eco- plants exposed to salt and water stress
systems and caused a large part of deser- (Boulghalagh et al. 2006). Most plants
tification and soil salinization (Sadio 1989, may be considered to be more sensitive to
Szabolcs 1992). salinity during their germination and emer-
Aleppo pine is a major forest tree spe- gence phases (Maillard 2001). Among the
cies in the Mediterranean basin, covering causes of inhibition of germination in the
more than 250,000 km2 (Quezel 2000). presence of salt, the change in hormonal
In Algeria it occupies 850,000 ha (Meza- equilibrium was evoked (Kabar 1987). A
li 2003). The pine forests have been ex- delay in the germination caused by salin-
periencing intense human pressure for ity was shown in several species (Ndour
centuries (clearing, illegal logging, fire, and Danthu 1998, Benata et al. 2006,
grazing), causing deforestation and de- Boulghalagh et al. 2006). Work carried
cline of native plants. Aleppo pine is the out on Halophytes showed that the inhib-
most widely used tree in the reforestation itory effect of NaCl on germination would
in arid and semi-arid degraded areas. It be essentially osmotic in nature, with salt
is characterized by relatively shorter life preventing the implantation of the seed
span, usually not exceeding 150 years. Its (Katembe et al. 1998).
growth can reach 10 m in 20 years. It is In relation to the above statements, the
a tree that has a pivoting rooting depend- aim of this work was to study the effect
ing on the nature of the soil and its fertility. of the main environmental constraints af-
Like other pines, it is a monoecious tree fecting seed germination of Aleppo pine,
characterized by winged seeds between including drought and salinity, modelled
5 and 7 mm in length (Bentouati 2006). in laboratory conditions. Aleppo pine was
Old Aleppo pine stands do not always re- selected as a subject of study because of
generate easily, except in the case of fire. the problems existing with its regeneration
Foresters encounter difficulties in regen- in arid and semi-arid areas, which are the
erating these mature stands, where the last ramparts against desertification.
regeneration is often absent. In this con-
text, managers seek to understand and
know the techniques and treatments that Materials and Methods
facilitate the natural regeneration of these
pine forests (Prévosto et al. 2009). Collection of Aleppo pine seeds
Seed dormancy is one of the toler-
ance mechanisms developed by plants Mature three-year-old cones were select-
found under conditions of high aridity, ed for our study. They were harvested in
temperature, and salinity (Fenner 1985). early August 2016. Further on, they were
The maintenance of plants under limiting put in plastic bags and exposed to the sun
environmental conditions is primarily de- for one or two months to allow the cones
pendent on the success of germination to burst and release the seeds (General
(Ungar 1982, 1991). Several factors inter- Directorate of Forests nursery Technique).162 M. Zouidi, A. H. Borsali, K. Hachem, A. Allam, A. Naimi, and I. Hakmi
Cones from older trees were harvested in of Algiers and about thirty kilometres to
the pinewood of Fenouane (geographic the west of Saida (BNEF 1990). It is man-
coordinates 34°30’13.08’’ N; 3°28’17.16’’ aged by the Conservation service of the
E) (Fig. 1), located in the territory of the forests of Saida and is part of the district
wilaya of Saida, some 550 km southwest of Ain El-Hajar wilaya of Saida (Algeria).
Fig. 1. Location of the harvest area of the Pinus halepensis grains
(BNEDER 1992, modified by Zouidi).
Effect of osmotic stress on plants (Romo et al. 2001), having a mo-
germination lar mass of 6000. Germination tests were
carried out with 20 seeds per petri dish
Integumentary inhibition was lifted follow- (diameter 9 cm).
ing a protocol that recommends disinfec- Each petri dish was coated with two
tion of seeds for 10 minutes in an 8 % sodi- layers of filter paper at optimum germi-
um hypochlorite solution and then rinsing nation temperature (20 °C). Polyethylene
the seeds by water several times followed glycol (PEG) 6000 solutions of increasing
by soaking the seeds in distilled water for concentrations and inducing also increas-
24 hours (Nedjimi et al. 2014). Germina- ing water potentials (by the equation es-
tion tests were carried out under different tablished by Michel and Kaufman (1973))
levels of water potentials through the use were used to induce the different levels of
of Polyethylene glycol (PEG), which forms osmotic stress tested. The water potential
a non-permeable, hydrosoluble non-ionic values tested were 0, -0.05, -0.25, -0.5,
polymer for the cells. It is used to induce a -1, and -2 bars. The duration of the test
water deficiency by reducing water avail- was set at the germination period, which
ability without causing physical damage to spread over 30 days, and the countingAssessing of the Tolerance of Pinus halepensis Mill. Seeds to Water and Saline ... 163
of the germinated seeds was done daily. (the time at which 50 % of the seed germi-
According to Michel and Kaufman (1973), nation is reached) (Côme 1970, Lachiheb
the equation (1) linking the various param- et al. 2004). It is expressed in equation
eters was as follows: (2):
Ψh = –(1.18∙10-2) C– (1.118∙10-4) C2 + V = T1 + [(0.5–G1/G2–G1)]∙(T2–T1), (2)
+ (2.67∙10-4) C∙T + (8.39∙10-7)∙C2∙T, (1) where: G1 (%) is the cumulative seed
where: Ψh – is water potential in bar; germination with a value closer to 50 %
T– incubation temperature in °C; C– con- (lower) and G2 (%) cumulative seed ger-
centration of PEG 6000 in g·L-1. mination with a value closer to 50 % (high-
er) (Lachiheb et al. 2004); T1 – number
of days is the cumulative percentage of
Effect of salinity on germination
sprouted seeds whose value is closer to
We conducted the germination tests un- 50 % (lower); T2– number of days is the
der saline stress using the optimum ger- cumulative percentage of sprouted seeds
mination conditions determined by previ- whose value is closer to 50 % (higher).
ous experiment. Seeds were germinated
in petri dishes on filter paper, watered dai- Statistical analysis
ly with distilled water containing different
concentrations of NaCl (0, 1, 2, 3, 4, and The results were subjected to analysis of
5 g·L-1) and arranged at optimum germi- variance (ANOVA) with a single factor of
nation temperature (20 °C) (Thanos and variation at 5 % probability level (P≤0.05)
Skordilis 1987). The test duration was de- after controlling normality distribution for
termined by the 30-day germination peri- comparing the averages of germination
od. Germination was monitored every 24 rates with stress. The post-hoc Fisher
hours, and germinated seeds were count- (LSD) test was applied for multiple com-
ed and removed from the batch. The time parisons of means. We used Statistica
taken for the germination percentages of software package version 7.0.
all replicas to reach 50 % was recorded as
TG50. The counting of germinated seeds
was carried out on a daily basis. Results
Parameters measured Effect of osmotic stress
on the germination
The germination rate for each batch (TG)
is the best indicator for identifying the con- Our results showed the effect of increas-
centration of PEG and NaCl that present ing PEG concentrations on Aleppo pine
the physiological limit of germination of seeds subjected to different osmotic
the seeds. It is expressed by the ratio of stresses. Thus for untreated seeds (con-
the number of seeds germinated to the to- trols) the germination rate was highest –
tal number of seeds. On the germination 90 % with a short latent phase that lasts
test the definitive percentage of germina- only six days. It was also noted that the
tion was determined (Agrobio 2013). The application of osmotic stress of (-1 bar)
rate of germination may be expressed by resulted in a low germination rate not ex-
the median germination time (Scott et al. ceeding 21 %, while there was no germi-
1984) or by the mean germination times nation at higher stress (-2 bar).164 M. Zouidi, A. H. Borsali, K. Hachem, A. Allam, A. Naimi, and I. Hakmi
The analysis of the variance (ANOVA trations of Polyethylene glycol (PEG 6000)
single factor) showed a highly significant on the rate and velocity of germination of
effect (PAssessing of the Tolerance of Pinus halepensis Mill. Seeds to Water and Saline ... 165
Fig. 3. Effect of different saline stress on the rate and speed of germination
of Aleppo pine seeds.
Note: The bars and whiskers represent the mean ± standard deviation (n=5 repetitions).
Significance levels: * – P166 M. Zouidi, A. H. Borsali, K. Hachem, A. Allam, A. Naimi, and I. Hakmi
most of the studies on the impact of os- a significant reduction in germination in %
motic stress on germination show that the at -2 bars, while root growth was assigned
germination rate decreases considerably to -4 bars. Different sources demonstrat-
with increasing the stress. Similar results ed significantly different responses to wa-
were obtained in various studies on Pinus ter stress. Our results showed that seeds
ponderosa Douglas ex C.Lawson and harvested in the semi-arid zone exhibited
P. eldarica Medw. (Djavanshir and Reid significantly different responses to water
1975), P. brutia Ten and P. eldarica (Cal- stress with great germination power under
amassi et al. 1980), P. taeda L. (Dunlap ideal conditions (control). On the other
and Barnett 1984), and P. halepensis and hand, those who have undergone stress
P. brutia (Thanos and Skordilis 1987). presented a low rate of germination and
In the absence of sufficient moisture, therefore are less resistant to the extreme
even if the seed is properly placed in the climatic conditions of the zone.
soil, it does not evolve, and in case of
drought persistence the situation can re-
Effect of saline stress on germination
sult in an absence of emergence (Feliachi
et al. 2001). The results of the variance analysis re-
Drought is one of the major environ- vealed significant differences in the ger-
mental factors that greatly affects the mination rate of Aleppo pine (PAssessing of the Tolerance of Pinus halepensis Mill. Seeds to Water and Saline ... 167
with consequences on the level of growth the salt seems to prevent the hydration
and metabolic activity (Belkhodja and Bid- of the seeds to reach the threshold when
ai 2004). The inhibitory effects of salinity germination becomes visible. This is also
on the germination process can also be due to the time required for the seed to put
explained by altered enzymatic activity, in place mechanisms allowing it to adjust
which is indispensable for cell reactivation its internal osmotic pressure and thus al-
during this phase. Thus, salinity inhibits lowing for a germination.
the activity of several enzymes (Larcher Sidari et al. (2008) showed that seed
1995). Our results clearly show that the germination and the activities of the main
seeds of Aleppo pine germinate better in enzymes involved in Pinus seed reserve
the absence of salt with a good concen- utilization (glyoxylate cycle enzymes) de-
tration rate and at a speed accelerate and creased with increasing PEG, NaCl and
even in a medium enriched with NaCl at seawater concentrations.
low concentration 1, 2, and 3 g·L-1.
Increasing of salt concentration to
5 g·L-1 NaCl alters the seed germination. Conclusions
Salt stress tolerance in pines is moderate-
ly low as shown by Rocco et al. (2013). In the arid and semi-arid zones of Alge-
In the presence of salt stress the pro- ria, the long-observed drought has clearly
teins in the Aleppo pine needles affected led to salinization of the soils. The com-
by stress include the proteins involved in bination of these two natural stresses
photosynthesis. Aleppo pine is affected becomes increasingly stressful for the
by high concentrations, which was report- germination and growth of plants in their
ed also for other species. For example, natural environment. The study of the
Bouda and Haddioui (2011) applied the germination of Aleppo pine is very import-
same treatment on Atriplex seeds, and ant since it is considered very important
found that the rate of germination inhibi- species for reforestation. It is introduced
tion of seeds stressed by NaCl stops at to restore the degraded areas and occu-
5 g·L-1. The decrease in germination rate pied bare land in steppe areas, in arid and
and the slowing of germination velocity of semi-arid zones. The main peculiarities of
seeds exposed to salinity is explained by the germ behaviour of Aleppo pine seeds
an increase in external osmotic pressure, in the face of abiotic stresses can be sum-
which affects the absorption of water by marized as follows: For water stress, the
seeds due to accumulation of Na+ and Cl- germination rate and the average daily
ions in the embryo (Groome et al. 1991). germination are strongly affected and de-
This toxic effect can lead to the alteration crease with increasing the concentration
of the metabolic processes of germination of added PEG. In the absence of stress,
and in extreme cases to death of the em- the maximum germination rate in the
bryo by excess of ions. Thus the emer- presence of sufficient moisture is about
gence of radicle would be controlled by 90 %. Stressed seeds did not withstand
the osmolality of the medium (Bruggeman more than -1 bar PEG with low germina-
et al. 2002). tion rates (21 %). For saline stress the
According to Bliss et al. (1986a) the species germinated better in a salt-free
delay in germination following the in- treatment (control) with a germination rate
crease in salt stress is due to the fact that of 89 % and an average daily germination168 M. Zouidi, A. H. Borsali, K. Hachem, A. Allam, A. Naimi, and I. Hakmi
of 2.96. On the other hand, the seeds with Algérien). Insaniyat. Revue Algérienne
a stress in the order of 4 g·L-1 NaCl have a d’Anthropologie et de Sciences Sociales
low germination rate of the order of 21 %. (53): 167–175.
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Abdelmoumen H., Misbah El Idrissi M. 2006.
ered an early criterion for selection of plant
Effet du stress salin sur la germination, la
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