é‘éis WWWIHHWHHWNJIHWIHHIHNHHWIIWIHHI

Iiimiiiiiiiiii

('7 /\ /\,

This is to certify that the

thesis entitled

'SALINITY EFFECTS ON ARGAN (ARGANIA SPINOSA (L.) SKEELS)
GEMINATION AND JUVENILE GROWTH

presented by

Janis Sipple Michmerhuizen

has been accepted towards fulﬁllment
of the requirements for

".5. degree in Forestry

 

 

Major professor

Date Augst 4, 1999

 

0-7639 MS U is an Affirmative Action/Equal Opportunity Institution

 

 

 

 

LIBRARY

Michigan State

University

 

 

PLACE IN RETURN BOX to remove this checkout from your record.
To AVOID FINES return on or before date due.
MAY BE RECAUiD with earlier due date if requested.

 

DATE DUE

DATE DUE

DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11/00 chlRCJDateDue.p65-p.14

 

SALINITY EFFECTS ON ARGAN (ARGANIA SPINOSA (L.) SKEELS)
GERMINATION AND JUVENILE GROWTH
By

Janis Sipple Michmerhuizen

A THESIS
Submitted to
Michigan State University
In partial fulﬁllment of the requirements
For the degree of

MASTER OF SCIENCE

Department of Forestry

1999

ABSTRACT

SALINITY EFFECTS ON ARGAN (ARGANIA SPHVOSA (L.) SKEELS)
GERMINATION AND JUVENILE GROWTH

By

Janis Sipple Michmerhuizen

Soil salinization is increasing in Morocco as a result of irrigation of agricultural
land. The argan forest in the Souss Valley region has been negatively impacted by urban
expansion and the increase in agricultural land. Additionally, both artiﬁcial and natural
regeneration efforts have had poor results. Seeds and seedlings of argan were exposed to
0, 2.5, 5.0, 7.5, and 10.0 g/l NaCl to determine the effect of salinity stress on germination
and growth. Ten seed accessions were selected, ﬁve from a coastal site and ﬁve ﬁ'om a

mountain site. Analysis of variance indicated survival, seedling growth, root length, root
‘ dry weight, and shoot dry weight signiﬁcantly decreased with increasing NaCl
treatments. There were some signiﬁcant differences in salinity effects among the
accessions; however, there was no signiﬁcant difference between the coastal and
mountain sites. In addition, root:shoot ratio for seedlings increased with increasing NaCl
treatments. Argan growth is severely reduced at salinity levels greater then 2.5 g/l NaCl
(3.9 dS/m) and the species is not likely to establish from seed on saline soils.

KEYWORDS: Argam'a spinosa, argan, salinity, germination, juvenile growth, Morocco

Cepyrisht by
JANIS SIPPLE MICHMERHUIZEN
1999

In memory of my father
Joseph Holland Sipple, Jr.

1925 — 1998

iv

ACKNOWLEDGEMENTS

My most sincere thanks to Professor Fouzia Bani-Aameur, who guided me
through this research and opened her laboratory to me. I am also indebted to Mohammed
Alouani, mammal Baroudi, Abdelaziz Zahidi, and Sou’ad Beulahbil. Without the help of
thesegraduatestudents, Iwouldhavebeenlostastheyhelpedmetoﬁndmywayaround
the university and to be resourceful. Mohamed and Brahim also took care of my
seedlings when I needed to be away. It was truly a pleasure to work with all ofthem and I
would welcome an opportunity to work with them in the ﬁrture.

Appreciation is extended to the William S. Fulbright Fellowship that ﬁrnded this
research, and to Université Ibnou Zohr in Agadir, Morocco where all the work took place.
Thanks also to the staff and associates at the Moroccan American Commission for
Education and Cultural Exchange, who oﬂ‘ered support throughout the project.

A very special thank you to Dr. Michael A Gold who helped me mold my ideas,
push for more, and guided me through writing of this thesis. At Michigan State
University, my thanks goes out to my committee Dr. Donald 1. Dickmann, Dr. Phu Van
Nguyen, and Dr. Arthur Cameron who have been patient with me as I have plodded
through the writing process and whose comments have only strengthened this thesis.

This thesis is dedicated to my parents, Joseph Holland Sipple, Jr. and Ruth B.
Sipple, who have always believed in me and encouraged me to pursue my dreams. I am
grateful for their unwavering support. Finally, my inexpressible thanks to my husband,
Steve, who has been beside me ﬁom the beginning and has encouraged to the end.

Without him, I would never have completed this thesis.

TABLE OF CONTENTS

LIST OF TABLES ................................................................................................... viii
LIST OF FIGURES ................................................................................................... ix
CHAPTER 1 — INTRODUCTION ............................................................................. 1
CHAPTER 2 — LITERATURE REVIEW ................................................................. 4
2.1. Argania spinosa (L.) Skeels ........................................................................... 4
2.1.1. Botany ................................................................................................. 4

2.1.2. Ecology ................................................................................................ 4

2.1.3. Distribution ......................................................................................... 7

2.1.4. Uses ...................................................................................................... 9

Oil ...................................................................................................... 9

Agroforestry ..................................................................................... 10

Wood ................................................................................................ 1 1

2.1.5. Silviculture ......................................................................................... ll
Propagation ..................................................................................... l 1

Establishment ................................................................................... 12

Management ..................................................................................... 13

2.1.6. Symbiosis ........................................................................................... 13

2.1.7. Limitation ......................................................................................... 13

2.1.8. Research ............................................................................................ 13

2.2. Degraded Land In Morocco ....................................................................... 15
2.2.1. Development of Salt-Affected Soils .................................................. 16

2.2.2. Salinity stress on ﬂora ....................................................................... 17

Salt Eﬂects on Germination .............................................................. 18

Salt Eﬂects on Growth ...................................................................... 19

CHAPTER 3 - GERMINATION AND SEEDLING STUDIES ............................. 21
3.1. Introduction ................................................................................................ 21
3.2. Site Descriptions ......................................................................................... 21
3.3. Materials and Methods ............................................................................... 23
3.4. Results ......................................................................................................... 26
Seed germination ........................................................................................ 26

Seedling survival ........................................................................................ 28

Seedling height growth ............................................................................... 30

Root length ................................................................................................. 33

Root dry weight .......................................................................................... 36

Seecﬂing root:shoot ratio ............................................................................ 39

3.5. Discussion .................................................................................................... 41
CHAPTER 4 - CONCLUSION ............................................................................... 45
4.1. Limitations of Study and Future Research ................................................ 45
Limitations ................................................................................................. 45

Future Research ......................................................................................... 45

4.2. Conclusions and Recommendations ........................................................... 46

BIBLIOGRAPHY .................................................................................................... 48

Table 1.

Table 2.

Table 3.

Table 4.

Table 5.

Table 6.

Table 7.

Table 8.

Table 9.

Table 10.

Table l 1.

Table 12.

LIST OF TABLES

AN OVA table for germination by geographic origin, accession and NaCl
treatments ................................................................................................. 27

ANOVA table for seedling survival by geographic origin, accession and
NaCl treatments ........................................................................................ 29

AN OVA table for total height growth by geographic origin, accession and
NaCl treatments in seedling study .............................................................. 31

AN OVA table of seedling height growth after 10 days of NaCl treatments by
accession and treatment ............................................................................. 32

AN OVA table of seedling height growth after 20 days of NaCl treatments by
accession and treatment ............................................................................. 32

AN OVA table for root length by geographic origin, accession and NaCl
treatments in germination study ................................................................. 34

AN OVA table for root length by geographic origin, accessions, and NaCl
treatments in seedling study ....................................................................... 34

Germinated stones (all accessions combined) by NaCl treatments and root
conditions aﬁer 21 days in germination study ............................................. 35

AN OVA table for root dry weight by geographic origin, accession and
NaCl treatments in germination study ........................................................ 37

ANOVA table for root dry weight by geographic origin, accessions, and
NaCl treatments in swdling study .............................................................. 38

ANOVA table for root:shoot length ratio by geographic origin, accessions,
and NaCl treatments in seedling study ........................................................ 39

AN OVA table for rootzshoot dry weight ratio by geographic origin,
accessions, and NaCl treatments in seedling study ...................................... 40

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Figure 7.

Figure 8.

Figure 9.

LIST OF FIGURES

Argan growing between Tiznit and Sidi Ifni where annual rainfall is

approximately 250 mm ............................................................................... 6
Argan growing southwest of Tiznit where annual rainfall is less than

100 nun ...................................................................................................... 6
Growth response to salinity (ﬁ'om BOSTID, 1990). ................................... 18
Percent germination by NaCl treatment levels, all accessions combined ...... 27

Percent germination of argan mds by accession, all NaCl treatments
combined. Bars with the same letters above are not signiﬁcantly diﬂ‘erent

(LSD 5%) ................................................................................................. 28
Percent of seedling survival by NaCl treatments, all accessions combined. Bars
with the same letters above are not signiﬁcantly diﬂ‘erent (LSD
5%). .......................................................................................................... 29

Cumulative height growth of surviving seedlings by NaCl treatment.
Note: all seedlings receiving salt treatments 7.5 g/l (0) and 10.0 g/l (El) died
after 40 days .............................................................................................. 31

Mean seedling height growth by accessions (growth data summed over all
NaCl treatment levels). Bars with the same letters above are not signiﬁcantly
diﬁ‘erent (LSD 5%) .................................................................................... 33

Root dry weight (--) (mean + standard error) and root length (—) (mean
with standard error smaller than size of point) by NaCl treatments, all
accessions combined, in germination study ................................................. 35

Figure 10. Mean root lengths by accessions, all NaCl treatments combined. Bars

with the same letters above are not signiﬁcantly diﬁ‘erent (LSD 5%) in
germination study ...................................................................................... 36

Figure 11. Mean root dry weights by accessions, all NaCl treatments combined. Bars

with the same letters above are not signiﬁcantly diﬁ‘erent (LSD 5%) in
germination study ...................................................................................... 37

Figure 12. Mean (+ standard error) dry weights for root and shoot by NaCl

treatments, all accessions combined ........................................................... 38

Figure 13. Average root:shoot length ratio by NaCl treatments. Bars with the same

letters above are not signiﬁcantly diﬁ‘erent (LSD 5%) in seedling study ...... 40

CHAPTERI

INTRODUCTION

Argan (Argania spinosa (L.) Skeels) is a medium-sized multipurpose evergreen
tree. It is the only arid zone species of the Sapotaceae family north of the Sahara Desert.
It is indigenous to Morocco and originates in the Souss Valley region. Although argan is
primarily regarded as an edible oil fruit tree (Sasson, 1993), and even though its
secondary products are of signiﬁcant value to the rural community and the ecosystem, it
has not yet been domesticated. Argan is also used for ﬁrel, timber, cosmetics, and valued
for its shade and role in stabilizing the soil. During summer drought, the leaves, fruits
and pressed seed cake are the only fodder available for livestock (Prendergast & Walker,
1992).

The argan forest ecosystem, which originally covered 1.4 million hectares, has
been reduced by over 40 % to approximately 800,000 hectares due to exploitation and
human pressure on land resources. In the semi-arid regions of southern Morocco, the
argan tree is of immense socio-economic importance. This native tree produces highly
nutritious edible oil, fodder (leaves and him) for livestock, and fuel (charcoal).
Historically, subsistence rural communities have relied on this forest ecosystem to
maintain their livestock herds and provide argan oil for consumption and sale. Today,
argan oil production continues to be a subsistence cottage industry managed by women
(Prendergast & Walker, 1992).

It has been speculated that natural argan regeneration has not been signiﬁcant for
the past 50 years. Government sponsored reforestation projects are attempting to

increase the argan population, though seedling survival has been low (Sasson, 1993).

Research into argan physiology has revealed many of the requirements and limitations
that argan seeds must meet or overcome in order to germinate and survive (Arif, 1994;
Nouaim & Chassoud, 1994; Nouaim et al., 1994; Farradous et al., 1996; Zahidi & Bani-
Aameur, 1997; Zahidi & Bani-Aameur, 1998). However, more research is needed in this
area to further deﬁne the tolerances of argan in both its natural habitat and in the nursery
environment. Additionally, research may prove that schottenol, an anticancer agent, can
be extracted from argan (Maurin, 1992; Sasson, 1993).

The cosmetic and the edible argan oil markets are strong within Morocco, and
there is growing international interest in argan oil for industrial cosmetic uses. Edible oil
also has international market potential because its nutritional value exceeds that of olive
oil. However, with the argan forest in a degraded state, the current market cannot be
expanded. Improved argan trees under cultivation could potentially produce as much oil
as olive trees.

The Souss Valley, where argan populations are the greatest, has experienced
urban expansion and intensiﬁcation of agriculture since the 1970s (Benchekroun &
Buttoud, 1989; Buttoud, 1990; Sasson, 1993). With the increase of agriculture and the
use of irrigation, the soil is highly susceptible to salinization. In 1976, Morocco had an
estimated 1,148 hectares of saline soils (Szabolcs, 1989). Current ﬁgures, while
unavailable, are most certainly higher in these arid and semi-arid regions.

Argan has been documented to be tolerant of all types of soils and soil conditions
with the exception of shifting sand (Gentil, 1906; Nouaim et al, 1991; Prendergast &
Walker, 1992). Nouaim et al. (1991) also stated that argan grows on saline soils;

however, there has been no study to determine the salinity tolerance of argan. Ifargan is

found to be tolerant of high salinity levels, it could be used to reclaim abandoned
agricultural land, prevent desertiﬁcation, encourage ecosystem restoration, and improve
the environment.

The goal of this research was to screen argan germplasm for salinity tolerance.
Accessions that perform the best under salinity stress will be recommended for
reforestation efforts on abandoned agricultural land. A salt tolerance range was

investigated as well as the effects of salinity on germination and seedling growth.

CHAPTER2

LITERATURE REVIEW

2.1. Argania spinosa (L.) Skeels

2.1.1. Botany

Argan is an arid zone evergreen tree in the Sapotaceae family. Within Sapotaceae,
Argania is the only genus found north of the Sahara desert and the genus is monospeciﬁc.
Argancanreach10mmheightwithadensecrownbetween20and40mindiameter.
Many trees have a single stem, but since they coppice well, and are subject to heavy use,
there are many with multiple stems. The leaves are small, lanceolate and leathery with a
dark green upper surface and a paler underside. Spines (modiﬁed stipules) up to 1 cm
long are at the base of the leaves. The ﬂowers are greenish yellow, 5-6 mm in diameter
and cluster in the leaf axils. The fruits are lime-green when developing and yellow when
mature; shape varies from nearly spherical to ovoid, and size ranges from 20 to 50 mm
The drape-like fruit consists of a tough pericarp and a smooth brown stone. The stone is
extremely hard and may have up to ﬁve seed chambers, with one chamber dominant (Bani-

Aarneur et al., 1998).

2.1.2. Ecology

Within the natural range, argan may be found at sea level up to the snow line of the
High Atlas (approximately 900 m and minimum temperature 38°C). In the Anti-Atlas the
upper limit is approximately 1300 m, as moisture becomes the limiting factor over
temperature. In the hottest months (June, July, August, September), temperatures oﬁen

exceed 50°C and lack of moisture becomes a limiting factor with temperature.

Average annual precipitation varies from 50 to 400 mm, and in the lower range, argan
takes on a bushy appearance (Figures 1 and 2) (Monnier, 1965; Nouaim et al., 1991;
Prendergast & Walker, 1992).

Argan is a shade intolerant tree and has never been documented as an understory
tree. The argan forest is described as a parkland, similar to the Spanish dehesa where the
crowns of trees rarely meet (Le Houérou, 1981; Montoya, 1984; Mellado, 1989;
Prendergast & Walker, 1992). Little is known about the root system, although it is
speculated that the taproot may reach depths greater than 30 m (Nouaim et al., 1991).

Argan achieves its best growth on the coastal plain where annual rainfall is 400
mm (Prendergast & Walker, 1992). It is found on marginal soils and has been assurned to
be tolerant of all soil types other than shitting sands; however, no studies have been found
which investigate soil and argan (Gentil, 1906; Nouaim et al., 1991).

Argan is very drought tolerant. Contributing to its ability to survive in arid regions
(50 mm of rainfall), the tree drops its foliage during prolonged droughts and remains in a
state of dormancy, sometimes several years, until rainfall returns (Morton & Voss, 1987;
Nouaim et al., 1991).

Argan sprouts vigorously and coppicing is considered the most reliable method for
the ﬁrst regeneration. However, the sprouts that arise alter a second cOppice are not
viable for maintaining a healthy tree. Seeds or seedlings are used to regenerate an area

after this second harvest (Morton & Voss, 1989; Sasson, 1993).

 

Figure 1. Argan growing between Tiznit and Sidi Ifni where annual rainfall is
approximately 250 mm.

 

Figure 2. Argan tree growing southwest of Tiznit where annual rainfall is
less than 100 mm.

2.1.3. Distribution

Argan was ﬁrst documented by Leo Africanus, a traveler who visited Morocco in
1510, and according to Monnier (1965), the original natural range was 1.4 million
hectares. The argan population experienced a decline in Morocco centuries ago when
migration into this region began. The total area of the Mediterranean zone once covered
by argan is still unknown; however, a recent ﬁnd of siliciﬁed wood ﬁagments on the
Mediterranean island of Sardinia closely resemble argan and has been dated back to the
Miocene period (roughly 25 million years ago). Because of this ﬁnd, there is speculation
that argan covered the entire Maghreb region (Morocco, Algeria and Tunisia) at one time
(Prendergast & Walker, 1992). However, the origin of argan is in the Souss Valley of
Morocco according to Mellado (1989).

During World War I the argan forest was harvested in large quantities to meet
export demands for fuel and to clear agricultural land. The Moroccan Forest Service
(during the French protectorate period 1912-1956) recognized that the harvests were
causing a loss of forest area and imposed restrictions on the trees in 1924. There was little
enforcement of this legislation, and during WWII the demand for ﬁre] increased once again
and the argan population was negatively impacted (Morton & Voss, 1987). In some areas
entire forests were destroyed and the 1994 Moroccan forestry map indicated 828,300
hectares remaining, with the majority in the southwestern part of the country (Maroc
Division de la Cartographic, 1994). Therewere two small forests outside this region, one
on the hillsides of Beni Snassen in northeast Morocco near Oujda and another southeast of

Rabat in Oued Grou (Nouaim et al., 1991; Prendergast & Walker, 1992).

Even more signiﬁcant than the estimated 40% decline in total area is that argan
tree density had been reduced by two-thirds by the late 1980s (Benchekroun & Buttoud,
1989; Prendergast & Walker, 1992). This is attributed to the Moroccan government
policy encouraging intensive agriculture in prime argan habitat in the 1970s, which
resulted in an increase of cleared land for cultivation and more irrigation. In addition,
many farmers removed argan near their ﬁelds because they attracted ﬁuit ﬂies, which
damaged their crops (Sasson, 1993; Mazih & Debouzie, 1996). Recognizing the
ecological value of argan to this region, an argan reforestation project was carried out in
1991, and about 3,000 hectares were regenerated. This was done mainly through
coppicing combined with protection from grazing. Additionally, 4,700 hectares of sand
dunes were stabilized through transplanting argan seedlings. The seedling survival has
been low and more research, especially in biotechnology, is being conducted to improve
survival (Sasson, 1993).

Unsuccessﬁrl attempts have been made to grow argan in the East Indies, Australia
(including Tasmania), South Africa, Kenya, Cyprus, England, Florida, Curacao, and Haiti
(Morton & Voss, 1987). Ten years ago, two argan plantations were established in the
Negev Desert in Israel. Fruiting began at both sites during the third and fourth year, and
this onset of ﬁ'uit outside its natural range is very promising (Nerd et al., 1994). Nerd et
al. (1998) has found regular ﬂowering and ﬁuiting in cultivated argan. Israel is now
investing in further research to explore the ﬁrture of commercial argan oil production
(Combating Desertiﬁcation, 1995). Spain has also documented argan trees growing in the
southern region (Montoya, 1984), though there are no reports of any commercial oil

production. Southern California also has a climate similar to southern Morocco, however

it is not likely to give higher economic yields than the current citrus production‘. At this

point in time, it appears that the majority of argan plant resources will remain in Morocco.

2.1.4. Uses

Although argan is primarily regarded as a fruit tree (Sasson, 1993), its secondary
products are signiﬁcant to the local economy, livestock rearing, and the ecosystem
During annual summer drought, the leaves, fruits and pressed seed cake are the only
fodder available for livestock (Prendergast & Walker, 1992). Argan is also used for fuel,
timber, cosmetics (oil and seed residue), and valued for its shade and role in soil
stabilization. Subsistence cultivation of barley is possible under the argan campy, where
the microclimate is greatly altered (Mellado, 1989).
Oil

A valuable edible oil is extracted ﬁ'om the seeds. The argan oil “industry” is based
on wild trees, as cultivars do not yet exist. In Morocco, argan oil is preferred over olive
oil; however, it represents only 1.6% of total annual edible oil consumption in Morocco.
This is probably due to low supply and the labor intensive, rudimentary and incomplete
extraction process (Sasson, 1993). Between seven and eight million working days are
devoted armually to argan oil production on a national level (Prendergast & Walker,
1992). Approximately 100 kg of fruits are needed to produce 1-2 kg of oil, 2 kg of

pressed md cake, and 25 kg of dried “husk” (Ehrig, 1974; Nouaim et al., 1991;

 

'Thesetworegionshavebeencomparednumeroustimes. Withenoughwater,Moroccohadhopedto
establishsimilaragriculturaloutputsassouthernCalifornia. Althoughalargeamountoflandisunder
irrigation, the outputs have been disappointingly low for Morocco (Swearingen, 1987).

Sasson, 1993). The labor intensive extraction process, usually carried out by women,
requires seed collection, breaking the seed husk, heating the seeds, then grinding the seeds
with water between stones. In total, this process takes 8—10 hours for 1-2 kg of oil
(Nouaim et al., 1991; Sasson, 1993). The oil is highly nutritious because it contains 80
percent polyunsaturated fatty acids of which 30 percent is linoleic, one of the most
important essential fatty acids in the human diet. Argan oil is a common part of the local
diet. It is often mixed with crushed almonds and honey into a thin butter (locally called
amalou) for eating with bread, mixed with barley and honey for a breakfast porridge, or
bread is simply dipped in the oil (Morton & Voss, 1987).

The oil is also desirable for cosmetics. It is believed to be good in protecting the
skin ﬁ'om aging by preventing wrinkles. This industry is quite small, partially due to the
laborious extraction process (Nouaim et al., 1991; Sasson, 1993). Locally, the residue
ﬁ'om the oil extraction process is used as a skin "mask” for the same reason.
Agroforestry

Argan is the tree component of an agrosilvopastoral system. In the system, barley
is planted in an entire plot of land, including the area underneath the tree canopy. Before
the barley plants send up the reproductive shoot or ﬂag leaf, livestock are permitted to
graze the green swards. The livestock are then moved off of the ﬁeld, and the barley is
allowed to grow and set seed to produce grain. It is the second growth that is harvested
for the cereal grain for human consumption. Other trees that may be a part of this system
include almond, olive, or date palms depending on the location in the country and site
characteristics. Literature sources ﬁ'equently mention the cultivation of barley with argan

(Monnier, 1965; Montoya, 1984; and Nouaim et al., 1991); however, no details of this

10

agrosilvopastoral system has been written. This argan-barley type of farming remains
common today along the slopes of the High and Anti-Atlas Mountains.

Argan leaves and ﬁ'uits are fodder for livestock during the summer drought.
Additionally, the pressed seed cake remaining after the oil has been extracted is fed to
livestock (Montoya, 1984; Prendergast & Walker, 1992).

Wood

The wood is yellow, hard, durable and dense making it desirable for implements
and utensils (Monnier, 1965; Morton & Voss, 1987). However, the wood is most often
used for fuel (dried or charcoal). In 1993, Sasson (1993) estimated that the argan forests

ﬁ'om the provinces of Agadir and Taroudant produced 20,000 tons of ﬁrewood.

2.1.5. Silviculture
Propagation

Two ﬂowering periods have been observed; the ﬁrst (or early) ﬁom October to
November, and second (or late) ﬂowering during February to March. However, trees
have been noted to have some ﬂowers throughout this period (October — March)
(Ferradous et al., 1995). Development of the ﬁ'uit takes 9 to 16 months, so it is possible
to see ﬂowers, mature ﬁ'uit and inunature fruit on one tree at the same time (Bani-Aameur
et al., 1998; Nerd et al., 1998). Since the ﬂowering cycles are not the same for every tree,
mature ﬁ'uits can be found throughout the year. However, for the largest quantity, fruits
are collected from May through June. It is important to note that some ﬁ'uits will be

aborted due to the Mt ﬂy (Ceratitis capitata), which lay eggs in the pulp, or for other

11

unknown reasons. The largest fruits should be selected and collecting directly ﬁ'om the
ground should be avoided.

Fruits should be placed in cool storage (4°C) to extend seed viability, however,
exactly how long the seeds will remain viable is not known at this time. To remove the
stone ﬁ'om the ﬁuit, crack the dried pulp (mesocarp) with a hammer. Germination is
higher if the seeds are not extracted ﬁ'om the stone. Also germination is higher and more
rapid when the stones are mechanically scariﬁed. Because of the presence of F miran
spp. and other fungi in the mesocarp, the stones should be cleaned with a 2% chlorine
solution for 15 minutes followed by three ﬁesh water rinses. After scariﬁcation, additional
treatment with a fungicide like Thiodan is recommended. Stones should be planted 1-2
cm below the soil surface, and if properly scariﬁed and ambient temperatures are above
10°C, complete germination will occur within 21 days (Zahidi & Bani-Aameur, 1997;
personal observation).

Establishment

Artiﬁcial regeneration continues to be difﬁcult. Zahidi and Bani-Aameur (1997)
recommend that container-grown seedlings should be at least 6 months old before out-
planting due to F usarium spp. They should be planted alter the ﬁrst rains to insure
suﬁcient moisture during the establishment period. Seedlings should also be protected
from grazing. More research is needed to determine the most effective establishment
techniques.

Research into rnicropropagation is being conducted with the support of the French
National Institute for Agricultural Research (NRA). At this time, in-vitro production is

only supplying plantlets for research (Sasson, 1993).

12

Management

Little is known about management. Argan sprouts vigorously and coppicing is
considered the most reliable method for the ﬁrst regeneration However, the sprouts that
come after a second out are not viable for maintaining a healthy tree (Morton & Voss,

1989; Sasson, 1993). To insure ﬁ'uit production trees in ﬂower should not be grazed.

2.1.6. Symbiosis
Argan tree roots contain endomycorrhizae, which enhance the water and nutrient
(especially phosphorus) uptake ability of the trees (Sasson, 1993; Nouaim & Chaussod,

1994; Nouaim et al., 1994).

2.1.7. Limitation

Argan is highly susceptible to F usarium spp., a problem for germinating seeds and
seedlings (Nerd et al., 1994; Zahidi & Bani-Aameur, 1998). Overall seedling survival
continues to be low and more research is needed (Sasson, 1993; Zahidi & Bani-Anthem,

1997).

2.1.8. Research

Physiology and artiﬁcial regeneration have been the primary focus of biological
research on argan. Sasson (1993) reported that several thousand seedlings are being
raised in nurseries. However, survival in both nurseries and alter out-planting is low due
to Fusarium spp. (Nerd et al., 1994; Zahidi & Bani-Amneur, 1998). Zahidi and Bani-
Aarneur (1998) discovered that some genotypes are more tolerant to this fungus and that
seedlings remain susceptible during the ﬁrst ﬁve months after germinating. Seed handling

before sowing has also been examined by Zahidi and Bani-Aameur (1997). They found

13

that a higher percentage of seeds germinated that had been stored for two years (60%)
than those stored for three years (50%). They also developed a protocol (see
Propagation) for reducing F usarium infection on germinating seeds (Zahidi & Bani-
Aameur, 1997).

Planting depth, scariﬁcation and temperature have all been found to affect argan
germination. Arif (1994) determined the optimum planting depth to be 2 cm. He also
found that surface sown seeds would not germinate. Scariﬁcation (cracking of stone)
results in both higher percent and more rapid germination. Seedling germination has also
been recorded to be aﬁ‘ected by low daily ambient temperature. Seeds sown on January
15 were signiﬁcantly slower in germinating and in attaining maximum germination in
comparison to the other two seed sets, which were sown in November and December. It
took longer for the seeds to begin germinating and to reach a maximum germination when
ambient temperatures had a daily mean of 12°C (range 7 .5°C and 20°C) compared to
22°C (range 15 — 28°C) in November and 18°C (range 12 - 25°C) in December (Zahidi &
Bani-Aameur, 1997).

In its natural habitat, mature argan seeds that fall by the end of September achieve
maximum germination (Metro 1952, Farradous et al. 1996). This is because the seeds will
beneﬁt ﬁ'om the rains of October, and later months, and the relatively moderate high
temperatures (> 25°C) (F erradous et al. 1996). Seeds that germinate later are subject to
longer periods of cooler temperatures and greater exposure to diseases. This may be a
cause for poor natural regeneration of argan (Zahidi & Bani-Aameur, 1997).

Nouaim and Chaussod (1994) studied the effects of inoculating microprogagated

seedlings with vesicular-arbuscular mycorrhizal (V AM) ﬁrngi, and found a signiﬁcant

14

increase in above-ground seedling biomass after six months. A subsequent study of the
mineral nutrient contents of the seedlings revealed greater mineral uptake in seedlings with
VAM ﬁrngi (Nouaim et al., 1994). This may explain the tree's ability to grow in low

fertility soils.

2.2. Degraded Land In Morocco

Morocco is the northwest corner of Aﬁica. The southern and southeastern portion
of the country is part of the Sahara Desert. Morocco, excluding the Western Sahara, has
69.5 million hectares of land; however, only 12.7% (roughly 8.8 million hectares) is
considered arable (Sasson, 1993). Eighty percent of this arable land is classiﬁed as arid or
semi-arid (El Mourid & Karma, 1996).

Land degradation, usuallytheresultofadversehumanimpaet, inaridandsemi-arid
regions generally results in desertiﬁcation (Daily, 1995). Land degradation in the
Mediterranean region is not a recent phenomenon. The over exploitation of the
Mediterranean vegetation in the Near East began during the Neolithic period (10,000 to
2,000 BC) when human population increased greater than tenfold. Since that time,
population has continued to grow and demands for building materials, fuel, and land for
agricultural production have increased. Most recently, in the last ﬁfty years, urban
expansion has had the greatest impact on the fragile Mediterranean environment of
Morocco, including the argan forests (Le Houérou, 1981; Melado, 1989). The Souss
Valley where are argan populations are the greatest has experienced urban expansion and
intensiﬁcation of agriculture since the 19703 (Benchekroun & Buttoud, 1989; Buttoud,

1990; Sasson, 1993).

15

Additionally, drought affects more than 60% of Morocco's arable land and soil
salinization is increasing (Janick, 1989; Sasson, 1993). In 1976, Morocco had 1,148
hectares of saline soils (Szabolcs, 1989). Current ﬁgures, while unavailable, are most
certainly higher due to the increasing irrigation in these arid and semi-arid regions over the

past 20.25 years.

2.2. 1. Development of Salt-Affected Soils

Salt-affected soils can be found on the ﬁve major continents. While they can be
found in most climatic conditions, they are more extensive in arid and semi-arid regions.
These soils are an issue for agriculture as the accumulation of salts alters soil properties
(physical, chemical and biological) and plant growth is inhibited in many species.
Throughout the world there are approximately 955 million hectares (roughly 10% of total
land surface) that are affected by salt and experience limited crop production (Szabolcs,
1989; Rhoades, 1990).

These soils are usually classiﬁed as saline, non-saline sodic, and saline-sodic. A
combination of two factors primarily determines which salt-aﬂ‘ected soil could develop in a
givensite: thetypeofsaltspresentandclimate. Saltsnaturallyoccurinallsoils
originating from mineral weathering. When water from rainfall, groundwater, or irrigation
passes through a soil, the salts are dissolved and moved along a drainage path, which is
ultimately to the sea. However, where drainage is limited, the water evaporates and salts
become concentrated. Salts can even ascend through the soil in arid and semi-arid regions
where evapotranspiration is very high. Over time, this results in saline lakes, brackish

groundwater, salt deposits, or salinized soil (Rhoades, 1990; Singer & Munns, 1991).

16

Soil salinization caused by irrigation is considered to be a secondary cause. While
an irrigation scheme provides a good growing environment for agricultural crops, the
irrigation water contains salt, even if only trace amounts. Ifnot leached out, soil
productivity is reduced when salts accumulate in the root zone (Fereres, 1983; Rhoades,

1990).

2.2.2. Salinity Stress on Flora

Plants respond diﬂ‘erently to salt-aﬂ‘ected soils. The degree of response generally
falls in three categories: salt-sensitive, salt-tolerant, and halophytic. Salt-sensitive plants
quickly show a decline in growth soon after the soil electrical conductivity (EC) is greater
than 4 deciSiemens per meter (dS/m)2 and may die at 6 dS/m. Salt-tolerant plants begin to
show decline around an EC of 10 dS/m; however, they may survive with poor growth in
EC levels up to 20 dS/m. Halophytic plants actually show improved growth in low salt
levels, but beyond EC levels of 25 dS/m, there is decline in growth (Figure l) (BOSTID,
1990). Agricultural crops are rarely halophytic. The salt-tolerant crops may be ﬁrrther
broken down into moderately and highly tolerant. Tolerance may also vary during the

diﬂ‘erent stages of plant growth and development.

 

’deciSiemenspermeter(dS/m)istheSIunitforelectriealconductivityandisapprordmatelyequaltog/l
dividedby.64(orECx.64=g/l).

l7

Halophytss

    

 

120

100

(percent)
8 8

 
 
 

Salt-Tolerant Crops

Salt-Sensitive Crops

RELATIVE CROP YIELDS

  

8

 

SALINITY. dS/m

Figure 3. Growth response to salinity (ﬁom BOSTID, 1990).

Salt Eﬁ‘ects on Germination

Most plants are far more sensitive during germination and seedling stages. In arid
and semi-arid regions, seed germination and seedling establishment are the two most
critical stages for survival (Kigel, 1995). When high concentrations of salt are present,
most seeds do not survive, including halophytes. However, in some halophytes,
germination of seeds may be inhibited by the presence of salt. This is caused by an
osmotically induced or enforced dormancy. These species would be considered to be salt-
sensitive or salt-tolerant at the germination level. Once the salt soil conditions reached a
low level, these seeds would germinate and potentially establish themselves before the salt

levels rose again (Ungar, 1995).

18

Salt Eﬂects on Growth
High salt concentrations in soil affect the growth of most plants. The maximum

amount of salt any plant can tolerate is variable among species. Primarily, moisture
availability is reduced; nutrient availability is altered; physical condition of the soil limits
root penetration; and/or speciﬁc ions become toxic.

Typically, soluble salts adversely aﬂ‘ect plant growth as a result of osmotic eﬁ‘ects
on the availability of soil water. The osmotic effect actually creates a physiological
drought for the plant (Abrol, 1986; Kaﬂtaﬁ & Bernstein, 1996).

Other salt damage has also been noted as increase in hydraulic resistance of roots
and leaves; alteration of hormone levels that inﬂuence growth rates; direct damage,
particularly to photosynethic mechanisms; and ion competition, thereby increasing enagy
to maintain the KzNa balance (Wild, 1973).

Salts may also induce toxic effects or deﬁciencies of speciﬁc ions (e. g. Cl, 804,

B). Baﬁuls and Primo-Millo (1995) found that salt is most damaging to the leaves of
Citrus spp. Their study determined that increasing concentrations of chloride in the
foliage corresponded with increasing leaf injury and defoliation. Whereas high salt levels
for Prunus spp. have shown leaf injury to be caused by boron toxicity (El Motaium et al.,
1994). High concentrations of NaCl may also interfere with uptake of other nutrients.
Osmotic and speciﬁc ion eﬂ‘ects are the main factors that reduce root growth under
salt stress. The osmotic eﬁ‘ects of high salt concentrations may be observed in root cell
size and rate of cell production, thus shorter and/or thicker roots. Also a higher
root/shoot ratio is often observed for plants experiencing salt stress because shoot growth

is inhibited before root growth (Kaﬂtaﬁ & Bernstein, 1996). Root dry weight has also

19

been documented to decrease with increasing salinity for salt-sensitive as well as salt-
tolerant species (T omar & Yadav, 1985; Gutierrez Boem et al., 1994; Bailuls & Primo-
Millo, 1995; Ungar, 1996).

Argan has been documented to be tolerant of all types of soils and soil conditions
with the exception of shiﬁing sand (Gentil, 1906; Nouaim et al., 1991; Prendergast &
Walker, 1992). Nouaim et al. (1991) also stated that argan grows on saline soils;
however, there has been no study to determine the salinity tolerance of argan. The natural
range of argan is being threatened by soil salinization and the germination and growth
response to such conditions should be investigated further.

Two experiments were conducted to screen argan accessions for tolerance to
salinity at both the germination level and seedling growth stage, and to observe the eﬁ'ects

of salt on root growth.

20

CHAPTERS

GERMINATION AND SEEDLING STUDIES

3.1. Introduction

The Souss Valley region, which has the greatest population of argan, has
experienced urban expansion and an increase in intensive and irrigated agricultural land in
the past 20 years. Inigation of these arid to semi-arid soils can easily lead to salinization
due to the low rainfall and high evapotranspiration if good drainage is not maintained
(J anick, 1989).

Artiﬁcial regeneration has been poor and natural regeneration has been practically
non-erdstent. While mature argan trees may be tolerant of saline soils (Nouaim et al.,
1991), seeds may not germinate and survive under high saline conditions. It is not known
at this time if argan seeds have a salt-induced dormancy; however, gibberillic acid (GA)
was used in this study to stimulate germination (Bewley & Black, 1994; Khan & Rizvi,
1994; Kahn & Ungar, 1998).

The objective of these studies was to screen argan accessions for salt tolerance at
germination and seedling stage and to observe the effects of salt on early root growth
Questions regarding germination, seedling mortality, seedling height growth, root length
and biomass, and rootzshoot ratios among salt levels, genotypes and geographic seed

origin relative to salt tolerance were investigated.

3.2. Site Descriptions
This experiment was carried out from November 1997 through May 1998 in the

Laboratoire de Recherche sur la Variabilité Génétique at the Faculté des Sciences campus

21

of Université Ibnou Zohr in Agadir, Morocco. Accessions were selected based on their
tolerance for F usarium spp. (Zahidi & Bani-Aameur, 1998) and growing location. Two
distinct geographic locations were chosen: a coastal site, Ait Melloul; and a mountain site,
Argana.

Five accessions were selected ﬁom each location. Five argan trees were selected
in Ait Melloul from those growing in the Horticulture Complex of the Hassan II
Agricultural and Veterinary Institute along the route from Agadir to Taroudant. For this
study, these accessions were called Ait Melloul (AM). This site was located
approximately 12.5 km east of the Atlantic Ocean and was approximately 35 m above sea
level. The bioclimate of this area is semi-arid and hot and is strongly inﬂuenced by the
proximity of the ocean keeping temperature extremes to a minimum (Emberger, 1955).
Over a thirty-two year period, the average seasonal temperatures were: fall 11.5°C, winter
9.0°C, spring 239°C, and summer 265°C. The majority of the annual rainfall occurs
between October and April with less than 250 mm per year cumulative precipitation
(F arradous et al., 1996). The soil is a calcareous, dark brown entisol/aridisol with a thick
calcium carbonate hardpan at a depth of 80 cm (8018 Maroc, 1997). Woody species
associated with argan on this site are Acacia gummifera, Ziziphus lotus, Rhus
pentqrhylla, Gymnosporia senegalensis and on the calcium crust Senecio
antheuphorbium (F arradous et al., 1996).

Another ﬁve accessions were selected ﬁ'om ﬁve trees in Argana (AR), located 60
km inland ﬁom the ocean on the southern slope of the High Atlas Mountains between
Marrakech and Agadir. The altitude of this interior mountain location is approximately

620 m and is semi-arid and cool; however, spring and summer temperatures are very hot

22

(Emberger, 1955). Over a seven-year period, the average seasonal temperatures were:

fall 6.7°C, winter s.s°c, spring 30°C, and summer 39°C. The majority ofthe atmttar
rainfall occurs between October and April and totals approximately 400 mm per year
(Farradous et al., 1996). The soil is an iron-rich red entisol (Sols Maroc, 1997). The
associated woody species on this site were Genista tricuspidata, G. ferox, Chamaecytusus
albidus (rare except at the base of the slope), Larmaea arborescens, Periploca laevigata,
and Salvia aegjptiaca. Other herbaceous plants were Cymbopogon schoenanthus,

ijarrhenia hirta, and Androcymbium gramineum (F erradous et al., 1996).

3.3. Materials and Methods

Fruits were collected during May and June 1997 and stored in plastic bags at room
temperature. Following a protocol for pretreatment of argan seeds set forth by Zahidi and
Bani-Aameur (1997), one hundred twenty him (60 for gerrrrination study and 80 for
seedling study) ﬁ'om each accession were hulled, stored in plastic bags, andplaced in cold
storage (4°C) for stratiﬁcation on December 1, 1997. Then on April 20, 1998, sixty of
these stones were soaked in 2% chlorine solution for 15 minutes and rinsed three times
with distilled water. The stones were scariﬁed by slightly cracking them between two
rocks and were immediately treated with the fungicide Thiodan and placed in the
reﬁigerator for overnight storage. Between scariﬁcation treatments for each accession,
the work area and rocks were cleaned with 10% chlorine solution to prevent
contamination. On April 21, 1999, the scariﬁed stones were soaked in a gibberellic acid
solution'(GAt at 1000 ppm) for 24 hours. The following day, April 22, 1999, the stones

were then rinsed twice with distilled water and placed in 9-cm glass petri dishes ﬁlled with

23

sterile vermiculite that had been moistened with the appropriate NaCl treatment solution
The petri dishes were placed on a laboratory bench according to the experimental design.
The mean temperature in the laboratory was 15°C (with a range of 12 - 20°C) during the
experiment.

This factorial experiment was arranged in a randomized complete block design
with two geographic origins, ﬁve accessions, ﬁve salt treatment levels, and three blocks.
Salt treatments were 0 M, 2.5 g/l (3.9 dS/m), 5.0 M (7.8 dS/m), 7.5 g/l (11.7 dS/m) and
10 g/l (15.6 dS/m) NaCl. Each petri dish contained four stones with a total of 150 petri
dishes used (600 stones). Treatment solutions were added as necessary to maintain moist
vermiculite during the experiment. The treatment solutions were made with 95% NaCl
and distilled water.

Seed germination was recorded daily. After twenty-one days, the root of each
stone (the longest root if multiple seeds germinated from one stone) was measured and its
fresh weight recorded. The roots were then placed in a 65°C oven for 24 hours. Each
stone in each dish was examined for number of seeds, condition of seeds (ungerminated,
healthy, dead), and presence or absence of ﬁrngus. The following day, the dried roots
were removed ﬁom the oven and dry weights were recorded.

. For the seedling study, eighty stones were removed ﬁ'om cold storage February 28,
1998, and the samepretreatment protocol was followed. On March 2, 1998, these stones
were then planted one to two centimeters below the surface (Arit; 1994) in ﬁve-liter pots
which had been ﬁlled with a 1:121 (peat mosszsandzargan forest soil) planting mixture.
Soil from the argan forest is rich in mycorrhizae, which upon inoculation, signiﬁcantly

increases initial growth of argan seedlings (Nouaim & Chaussod, 1994). Each pot

24

contained four stones with a total of 200 pots (800 stones) used. The experiment location
was outside in an open area away ﬁom the university buildings as well as tall trees.

This factorial experiment was arranged in a randomized complete blockdesign
with two geographic origins, ﬁve accessions, ﬁve salt treatment levels, and three blocks.
Salt treatments were 0 g/l, 2.5 g/l (3.9 dS/m), 5.0 g/l (7.8 dS/m), 7.5 g/l (11.7 dS/m) and
10 g/l (15.6 dS/m) NaCl. The amount of salt in the tap water was considered negligible.

From March 1 to May 1, 1998, the pots were irrigated with tap water to maintain
ﬁeld capacity (approximately 175 ml/pot/day). Care was taken to avoid through-ﬂow of
water to prevent leaching. Germination began on March 26, 1998 (day 25) and leveled oﬂ‘
thirty-seven days later. On May 2, 1998, the oldest, healthy seedling in each pot was
selected and all other seedlings were removed. Initial height measurements were taken for
each seedling. Fourteen pots did not have seedlings that were healthy and at least 10-days
old. These have been treated as missing plots. For eight weeks (53 days), salt treatments
were then added to the irrigation water according to the experimental design.

Seedling height measurements were taken every ten days and any dead seedlings
were harvested. Fifty-three days after treatments began, all remaining seedlings were
harvested. Shoot and root length measurements were taken for each seedling. Next the
root and shoot were separated and then placed in a 65°C oven to dry for 24 hours. Dry
weights were recorded for each root and shoot the following day. Diameters were less
than one centimeter for all seedlings and were not recorded.

On the ﬁrst day of salt treatment, seedling height varied ﬁom l to 12 cm. In order
to compare seedlings, growth was calculated aﬁer each measurement. The recorded data

for both studies were analyzed by general factorial analysis of variance (AN OVA) using

25

SPSS for Windows release 8.0. Where signiﬁcance was found, least signiﬁcant diﬁ‘erence
(LSD) were determined among the means (p<0.05). Data summaries and ﬁgures were

made using of Microsoﬁ Excel 7.0.

3.4. Results
Seed germination

Accessions were signiﬁcantly diﬂ'erent for germination; however the geographic
origin, salt treatments, and interactions were not signiﬁcant (Table 1). Germination
peaked after 19 days and overall, forty-seven percent of the seeds germinated. The
highest percent germination was found in the control and decreased with higher salinity
levels (Figure 4). One accession from Ait Melloul (AM 105) and two accessions ﬁ'om
Argana (AR 17 and AR 22) had combined germination greater than 60 %. The lowest
germination was less than 30 % from AM 97 (27 %) and AR 102 (23 %) with a total

germination range of 23-68%.(17 igure 5).

26

Table 1. AN OVA table for germination by geographic origin, accession, and NaCl
treatments.

Dependent Variable: Number of germinated seeds
df Mean F

 

 

 

 

 

 

 

 

 

 

    

 

Source S Sig.
quare
Block 2 1.2 0.7 .479 ns
Origin 1 2.9 1.9 .175 ns
Accession 4 4.7 3.0 .022 " .
Treatment 4 2.3 1.4 .212 ns
Origin ° Accession 4 0.8 0.5 .750 ns
Origin * Treatment 4 0.8 0.5 .750 ns
Accession " Treatment 16 1.8 ' 1.2 .303 ns
Origin "' Accession "' Treatment 16 0.8 0.5 .922 ns
Error 98 1.6
Total 149
CV = 24.4% " signiﬁcance at 5%
100 1'
m ..
w ..
3 7o .. _____________ our NaCl
60" ’r” ’._._ __._,..._. zsmm
50 T ’ I ’ ’. __ . .v
40.. /___,/' -- -- sown-er
I" . ' 7.5 on NaCl
30 " — - - — - roan NaCl
m 4
10 'i
o .

 

5 0 7 8 0101112131415101718192021
dayaoﬂrsatmant

Figure 4. Percent germination by NaCl treatment levels, all accessions combined.

27

l

l

Germination (94)
988398938

 

 

Figure 5. Percent germination of argan seeds by accession, all NaCl treatments combined.
Bars with the same letters above are not signiﬁcantly diﬂ‘erent (LSD 5%).

Sewing survival
Salt treatment signiﬁcantly affected seedling survival (Table 2) and survival

decreased with each increasing salt level (Figure 6). No signiﬁcant diﬂ‘erences were found

for geographic origin of the seeds, accessions, interactions (Table 2).

28

Table 2. ANOVA table for seedling survival by geographic origin, accession and NaCl
treatments. '

Dependent Variable: Seedlianurvival

 

Mean

 

 

 

 

 

 

 

 

Source df F Sig.
Square -
Block 3 0.1 1.6 .189 ns
Origin 1 0.0 0.7 .391 ns
Accession 4 0.1 1.2 .300 ns
Treatment 4 7.0 114.9 ,000 "
Origin " Accession 4 0.1 1.6 .188 ns
Origin * Treatment 4 0.1 1.6 .188 ns
Accession " Treatment 16 0.0 0.7 .772 ns
Origin "‘ Accession ° Treatment 16 0.0 0.8 .637 ns
Error 147 0.1
Total 199
CV = 52.6% ‘1' signiﬁcance at 1%

survival (16)

d d

 

p-
db
--

 

50 oil 7.5 all 10.0 all
NaCl treatment levels

Figure 6. Percent of seedling survival by NaCl treatments, all accessions combined. Bars
with the same letters above are not signiﬁcantly different (LSD 5%).

29

Seecﬂing height growth

AN OVA showed highly signiﬁcant aﬂ‘ects on height growth for accessions and
treatments, but not for geographic location or interaction (Table 3). Growth decreased
with increasing salt levels (Figure 7). All seedlings in the upper two salt levels (7.5 g/l and
10.0 g/l) died after 40 days of treatment (Figure 7). Height growth signiﬁcantly decreased
with each increasing salt treatment, with the two highest performing similarly (Figure 7).
Additionally, no signiﬁcant difference among treatments were noted until after 20 days of
treatment (Tables 4 and 5). Alter eight days of treatment, salt became visable on pots
receiving 5.0, 7.5, and 10.0 g/l NaCl. It is estimated that aﬁerlO days of treatment, salt
accumulates had reached 0, 4.4, 8.8, 13.1, and 17.5 g NaCl in each respective treatment
level. After 20 days, these accumulations were approximately 0, 8.8, 17.5, 26.2, and 35.0
g NaCl respectively.

Some accessions performed better under the salt treatments (Figure 8). An
accession from Argana (AR 99) showed the greatest mean height growth under all the
treatment levels. The next greatest height growth came from the site Alt Melloul (AM

97); the remaining accessions had similar growth.

30

Table 3. ANOVA table for total height growth by geographic origin, accession and NaCl
treatments in seedling study. '

Dependent Variable: Total growth (cm

 

 

 

 

 

 

 

 

 

Source df Mean F Sig.
Square

Block 3 7.1 2.2 .088 ns
- Origin 1 2.5 0.8 .375 ns

Accession 4 27.2 8.5 .000 “

Treatment 4 166.1 52.0 .000 "“"

Origin ° Accession 4 5.7 1.8 .135 ns

Origin "' Treatment 4 5.5 1.7 .151 ns

Accession "' Treatment 16 4.4 1.4 .162 ns

Origin " Accession "' Treatment 16 2.3 0.7 .779 ns

Error 147 3.2

Total 199

CV = 7.5% " signiﬁcance at 1%

Height growth (cm)
ewwe'snsass»
00000000

11111111

 

 

0.0 l I i l 1
Day 0 Day 10 Day 20 Day 30 Day 40 Day 50

Length of NaCl treatment

 

Figure 7. Cumulative height growth of surviving seedlings by NaCl treatment. Note: all
seedlings receiving salt treatments 7.5 g/l (0) and 10.0 g/l (D) died after 40 days.

31

Table 4. ANOVA table of seedling height growth after 10 days of NaCl treatments by
accession and treatment.

Dependent Variable: Growth at day 10

 

 

Mean

Source df Squar F Sig.
e

Block 3 1.3 2.8 .043 ‘
Accession 9 1.3 2.9 .004 “
Treatment 4 0.5 1.0 .382 ns
Accession "' Treatment 36 0.4 0.9 .630 ns
Error 147 0.4
Total 199

 

 

 

 

 

 

 

° signiﬁcance at 5%; " signiﬁcance at 1%

Table 5. AN OVA table of seedling height growth after 20 days of NaCl treatments by
accession and treatment.

Dependent Variable: Growth at day 20

 

 

Mean .

Source df Square F Srg.
Block 3 0.7 1.4 .243 ns
Accession 9 1.4 2.9 .004 ""
Treatment 4 5.5 11.4 .000 "
Accession " Treatment 36 0.5 1.1 .322 ns
Error 147 0.5

Total 199

 

 

 

 

 

 

 

‘”" signiﬁcance at 1%

32

Growth (em)

 

Figure 8. Mean seedling height growth by accessions (growth data summed over all NaCl
gestment levels). Bars with the same letters above are not signiﬁcantly diﬂ'erent (LSD
Root length

Analysis of variance (AN OVA) for root length showed high signiﬁcance within
treatments and accessions for the germination study (Table 6); however, no signiﬁcance
was seen in the seedling study (Table 7). Neither study found signiﬁcance for geographic
origin or in the interactions (Table 6 and 7). In the germination study, salt treatments
reduced root growth with increasing levels (Figure 9). The ﬁrst three treatments were
each sigrniﬁcant when looking at least sigrniﬁcant diﬂ‘erence (LSD), while the two highest
treatment levels were not signiﬁcantly diﬂ‘erent (LSD 5%). As salt treatment levels
increased beyond the 5.0 g/l treatment, root death sigrniﬁcantly increased. Over 50% root
mortality was evident at 7.5 g/l and that increased to over 80% at 10.0 g/l (Table 8).
Accessions AM 34, AM 17 and AR 71 showed the longest root lengths while AR 102 and

AR 99 showed the shortest (Figure 10).

33

Dependent Variable: Root length (cm)

Table 6. AN OVA table for root length by geographic origin, accession and NaCl
treatments in germination study.

 

 

 

 

 

 

 

 

 

Source df SMean F Sig.
quare

Block 2 32.0 2.1 .123 ns
Origin 1 39.6 2.6 .107 ns
Accession 4 52.5 3.5 .010 ”
Treatment 4 504.5 33.7 .000 “
Origin "' Accession 4 6.3 0.4 .794 ns
Origin " Treatment 4 4.7 0.3 .868 ns
Accession "‘ Treatment 16 6.7 0.4 .965 ns
Origin " Accession " Treatment 16 3.2 0.2 .999 ns
Error 98 15.0
Total 149

CV = 5.6% ” signiﬁcance at 1%

Table 7. AN OVA table for root length by geographic origin, accessions, and NaCl
treatments in seedling study.

 

 

 

 

 

 

 

 

Dependent Variable: Root len . h (cm

Source df Mean F Sig.
Square

Block 3 50.6 0.4 .732 ns
Origin 1 25.4 0.2 .643 ns
Accession 4 273.5 2.3 .059 ns
Treatment 4 251.6 2.1 .079 ns
Origin * Accession 4 114.7 1.0 .423 ns
Origin "' Treatment 4 280.3 2.4 .054 ns
Accession * Treatment 16 147.2 1.2 .236 ns
Origin " Accession * Treatment 16 173.8 1.5 .115 ns
Error 147 1 17.6
Total 199

CV = 1.0%

34

 

30.0 -—.

 

 

 

25.0 «~ I
20.0 .. """"""" I ...........
15.0 -- '°°' 1%?”m I'm.
10.0 -<- N - .
5.0 0 root length (nun) ---- i
0.0 : l : : ‘3 r
0 2.5 5.0 7.5 10.0

NaCl treatments (all)

Figure 9. Root dry weight (--) (mean + standard error) and root length (—) (mean with
standard error smaller than size of point) by NaCl treatments, all accessions combined, in
germination study.

Table 8. Germinated stones (all accessions combined) by NaCl treatments and root
conditions aﬁer 21 days in germination study.

 

 

 

 

 

 

 

NaCl Germinated Healthy roots Dead roots
Treatment # % # % # %

control 87 72.5 79 90.8 8 9.2
2.5 M 71 59.2 66 93.0 5 7.0
5.0 g]! 50 41.7 42 84.0 8 16.0
7.5 y] 43 35.8 20 46.5 23 53.5
100$ 34 28.3 6 17.6 28 82.4

 

 

 

 

35

 

6.0 ~
5.0 -

Root length (mm)

 

 

9910.“?
00000
lllll

AMAMARAMARAMARAMARAR
3417 7110522 617 9710299

Accession

Figure 10. Mean root lengths by accessions, all NaCl treatments combined. Bars with
the same letters above are not signiﬁcantly different (LSD 5%) in germination study.
Root dry weight

The germination study found highly signiﬁcant differences for root dry weight
between salt treatments and accessions, however neither geographic origin nor
interactions were signiﬁcant (Table 9). Root dry weights declined as salt treatment levels
increased (Figure 9). Two accessions from Argana (AR 22 and AR 71) performed the
best, while AR 102 performed the worst (Figure 11).

Root dry weight in the seedling study was signiﬁcant for salt treatments (Table 10)
and decreased with increasing salt treatment levels (Figure 12). No signiﬁcance was found

for geographic origin, accession, or interactions (Table 10).

36

Table 9. ANOVA table for root dry weight by geographic origin, accession and NaCl

 

 

 

 

 

 

 

 

 

treatments in germination study.
Dependent Variable: Root dry weight (mg)
Source df Mean F Sig.
Square
Block 2 51.7 0.5 .621 ns
Origin 1 0.3 0.0 .956 ns
Accession 4 434.9 4.0 .005 ‘”"
Treatment 4 1689.2 15.7 .000 "
Origin "' Accession 4 141.7 1.3 .270 ns
Origin " Treatment 4 51.4 0.5 .753 ns
Accession " Treatment 16 37.2 0.3 .991 ns
Origin " Accession " Treatment 16 35.5 0.3 .993 ns
Error 98 107.9
Total 149
CV = 2.8% 1" signiﬁcance at 1%
25.0 ~

3
‘3

Root dry weight (g)
3 a
O O

 

 

Figure 11. Mean root dry weights by accessions, all NaCl treatments combined. Bars
with the same letters above are not signiﬁcantly different (LSD 5%) in germination study.

37

Table 10. AN OVA table for root dry weight by geographic origin, accessions, and NaCl

 

 

 

 

 

 

 

 

 

 

 

 

treatments in seedling study.

Dependent Variable: Root dry weight (mg)

Source df Mean F Sig.
Square

Block 3 815.8 0.2 .913 ns
Origin 1 8713.8 1.9 .174 ns
Accession 4 9637.1 2.1 .089 ns
Treatment 4 2100723 45.0 .000 "
Origin "' Accession 4 8143.0 1.7 .144 ns
Origin "' Treatment 4 6900.5 1.5 .212 ns
Accession "' Treatment 16 2597.2 0.6 .912 ns
Origin " Accession "' Treatment 16 5410.6 1.2 .309 ns
Error 147 4672.3
Total 199

CV = 0.2% ” signiﬁcance for 1%

7°°1

000 r
"‘ 500
E m-

m J
5‘ 200

100 -

0
camel 2.5 on 5.0 on 7.5 an 10.0 on
NaClTnadmari

Figure 12. Root and shoot dry weights (mean + standard error, if no line then are is
smaller than data point) of dead seedlings by NaCl treatments, all accessions combined.

38

Seeding root'shoot ratio

Rootzshoot ratio calculated on both length (Table 11) and dry weight (Table 12)
basis was signiﬁcant among the salt treatments. The ratio increased for each salt level
except 10.0 g/l, which decreased in comparison to 5.0 g/l and 7.5 g/l; however, this was
not signiﬁcantly diﬁ‘erent from the other treatment levels, with the exception of the control
(LSD 5%) (Figure 13). No signiﬁcance was found for accessions or geographic seed

origin (Tables 11 and 12).

Table 11. ANOVA table for root:shoot length ratio by geographic origin, accession and
NaCl treatments in seedling study.

Dependent Variable: Rootshoot length ratio

 

 

 

 

 

 

 

 

 

Source df SMean F Sig
quare

Block 3 1.5 0.6 .642 ns
Origin 1 4.0 1.5 .225 ns
Accession 4 5.1 1.9 .113 ns
Treatment 4 14.4 5.4 .000 "
Origin " Accession 4 3.2 1.2 .322 rns
Origin "' Treatment 4 3.6 1.3 .260 ns
Accession " Treatment 16 3.0 1.1 .328 ns
Origin " Accession "‘ Treatment 16 3.0 1.1 .335 ns
Error 147 2.7
Total 199

CV = 11.4% " signiﬁcance at 1%

39

Table 12. ANOVA table for rootzshoot dry weight ratio by geographic origin, accession
and NaCl treatments in seedling study.

Dependent Variable: Rootzshoot dry weight ratio

 

 

 

 

 

 

 

 

 

   

Source df Mean F Sig.
Square
Block 3 0.0 0.2 .886 ns
Origin 1 0.1 4.6 .034 ns
Accession 4 0.0 1.4 .252 ns
Treatment 4 0.1 4.0 .004 ”
Origin * Accession 4 0.0 1.0 .424 ns
Origin "' Treatrnernt 4 0.0 1.0 .385 ns
Accession " Treatment 16 0.0 0.6 .911 ns
Origin " Accession " Treatment 16 0.0 1.2 .239 ns
Error 147 0.0
Total 199
CV = 68.8% "" signiﬁcance at 1%
5.0 --

3 4.0 ~-

:2

§ 3.0 ~-

§ 2.0 T

‘3

mo 1.0 --

0.0 ~

 

control 2.5 on 5.0 on 7.5 on 10.0 all
NaCl Treatments

Figure 13. Average rootzshoot length ratio by NaCl treatments, all accessions combined.
Bars with the sarrne letters above are not signiﬁcantly different (LSD 5%) in seedling
study.

40

3.5. Discussion

The salt treatment levels in these experiments ranged ﬁ'om slightly saline to
strongly saline (Abrol, 1988). Salt sensitive plants will be adversely aﬁ‘ected by salinity at
2-5 dS/m (1.3-3.2 g1 NaCl), while salt tolerant plants are not adversely aﬁ‘ected until
salinity reaches 10 dS/m (6.4 g/l NaCl). The growth of halophytes are stimulated between
5 and 15 dS/m (3.2-9.6 g/l NaCl) and may decline when salts exceed 25 dS/m (16 M
NaCl) (BOSTID, 1990). The argan seedlings showed no increased growth and signiﬁcant
negative aﬁ'ects were recorded at the lowest salt level (2.5 g/l NaCl or 3.9 dS/m).

Root growth and root dry weight showed decreasing values with increasing salt
treatments with the exception of germination. It is possible that the effects of GA negated
saline eﬂ‘ects on argan germination (Bewley & Black, 1994; Khan & Rizvi, 1994; Khan &
Ungar, 1998). However, for those argan seeds that did germinate, growth was negatively
impacted under saline conditions as most plants are in arid and semi-arid regions (Kigel,
1995). Tomar and Yadav (1985) found that Acacia nilorr'ca, Eucabputs hybrida and
Prosopisjulr'ﬂora all signiﬁcantly decreased growth and dry weight when salirnity levels
reached 7 dS/m. Conversely, germination of the salt-tolerant companion crop of argarn,
barley, is not severely inhibited by saline conditions until 12 dS/m (Abrol, 1988).

Based on the results of these studies, there were no salt tolerance diﬁ‘erences
evident due to the two geographic origins of seeds. However, there was some variation in
salt tolerance among individual accessions. The best germination and root growth was
seen in accessions AM 105, AR 17 and AR 22. The seedling study did not reveal one or

more accessions performing better than the others. Some accessions may be more tolerarnt

41

of saline conditions than others. However, more research is needed to determine a clear
salt tolerance range for argan at each developmental stage (germination, establishment,
and maturity). As this tree has yet to become domesticated, there may be other accessions
that have a greater tolerance to salinity.

After 21 days, the end of the germination experiment, argan germination indicated
a clear and consistent pattern. As salt treatment levels increased, percentage of
germination declined. Arid and semi-arid plants have diﬂ‘erent germination strategies in
establishing themselves in this harsh climate. There are many environmental factors (e.g.
water availability, temperature, light, salinity) that interact and regulate seed germination
(Kigel, 1995). Ungar (1995) found that some seeds have a salt-induced dormancy where
seeds remain dormant until saline conditions cease to be present. In this study, the
environmental factors were kept at optimal levels, with the exception of salinity. It is
possible that argan seeds may have a salt-induced dormancy, however it is not clear from
this study as gibberellic acid (GA) was used to stimulate germination (Bewley & Blaclg
1994; Khan & Rizvi, 1994; Khan & Ungar, 1998). It would be valuable to repeat this
study without GA to determine possible seed dormancy.

The clear decline in dry weight, both root (for both studies) and shoot, with
increasing salt treatment levels is consistent with other salinity studies. Gutierrez Boem et
al. (1994) examined the eﬂ’ects of salinity on rapeseed (Brassica napus) and found the
root dry weights decreased with increasing salinity. Ungar (1996) found the same results
with the halophytic grass, Am'plex panda. Similarly, studies on trees (Prosopr’sjuliﬂora,

Acacia nilotica, Eucalyptus hybrida, and Citrus spp.) found the total plant dry weight

42

decreased with increasing salinity treatments (Tomar & Yadav, 1985; Baﬁuls & Primo-
Millo, 1995).

Barley which is grown with mature argan trees is highly salt tolerant. At an EC
level of 10 dS/m, barley germination is still greater than 60% (Abrol, 1988). More
research is needed to determine if mature argan is more tolerant of salinity than at the
establishment stage. It may be that mature argan trees have root systems which extend
below the salt-affected soil. With irrigatiorn, however, the salts may be leached to tlwse
lower levels and cause decline for even the established mature argan trees.

The response of gowth and rootzshoot ratio was indicative of a plant under salt
stress. As Kaﬂcaﬁ & Bernstein (1996) noted for plants experiencing salt stress, argan
shoot growth was affected while the roots were not. Only in the highest treatment level
(10.0 M NaCl) was root length reduced, however, it was not statistically signiﬁcant.

Kigel (1995) found that seed germination and seedling establishment are the two
most critical stages for survival in arid and semi-arid regions. In the gerrnirnation study,
argan germination was negatively impacted by salirnity. Results from this study
demonstrated that argan seedlings were also salt sensitive, and the planting of argan in
saline soils should be avoided. It is possible that older seedlings, which had hardened oﬂ‘
or become ligniﬁed, may have yielded different results. Further study using lower salt
treatments would be helpful to deﬁne argan salt tolerance limits.

Lastly, the data questions the common perception documented by Nouaim et al.
(1991) that argan gows in saline soils. The results strongly indicate that argan is salt

sensitive and should not be gown under saline conditions. While it is possible that

43

established argan trees continue to grow when surface soil has become saline, additional

research is needed give a deﬁnitive answer.

CHAPTER 4
CONCLUSION

4.1. Limitations of Study and Future Research
Limitations

One limiting factor that pushed back the start date of both experimernts was
ambient temperature. Even though the argan fruits were available and ready for planting
by January 1, 1999, it was too cold to plant the seeds (<10°C). By March, the
temperature rose to above 10°C and the seedling study was initiated. It was not until
mid-April that the temperatures inside the university buildings rose above 10°C allowing
for better conditions for the germination study.

The geater limitation was time. This was partly due to the delay caused by cold
temperature and also the time ﬂame of the funding grant. Thus, experimental designs
that could be adequately carried out with the remaining time of the grant had to be used.

Besides time and weather, argan seed viability is still very unreliable which
resulted in fourteen missing plots for the seedling study. Working within this limitation,
however, is not difficult. Pregermination of argan is highly recommended before
transplanting for research purposes.

Future Research

In carrying out this research, it became clear that argan seed viability needs
further investigation. Determining the maximum storage life at room temperature and in
cold storage will help prevent using non-viable seeds. In addition, developing protests

that would remove immature 0r rotten seeds before planting would greatly improve

45

current practices. One possibility might be to develop a ﬂoatation test such as one used
with acorns (T eclaw & Isebrands, 1986).

While the experiments carried out in this paper determined that argan is salt-
sensitive, another study to determine seed dormancy caused by salt would enhance our
understanding of argan’s attempt in surviving in the arid and semi-arid regions. The salt
treatments of the seedling study were cumulative. To better understand the eﬂ‘ects on
juvenile growth, a similar study with constant soil salinity levels may reveal accessions
which could survive on moderately saline.

Additionally, a long-term study should be initiated to investigate the effects of
salinity on mature trees. This study should attempt to model the current irrigation
practices of the Souss valley where the tree is rapidly declining. Lastly, understanding
the agrosilvopastoral system with argarn, barley and livestock would also help to discover

desirable traits of this wild tree and its interactions with crops and livestock.

4.2. Conclusions and Recommendations

Argan seeds and seedlings are negatively affected by salt. In slightly saline soil
(2 dS/m) argan exhibited stress typical of other salt-sensitive plants. It is possible that
argan seeds have a salt-induced dormancy that protect them ﬁ'om germinating during
periods of high salinity; however, it also appears that seed viability is short allowing for a
very narrow window of opportunity for establishment.

Both studies examined argan during the establishment phase, which is considered
the most critical in arid and semi-arid regions. While these results cannot give a clear salt
tolerance range for this phase, it is evident that argan cannot establish itself on salt-

affected soils or with saline irrigation. It is also possible that if salt treatments were

46

begun aﬁer the seedlings had become ligniﬁed, the results would have been different.
Many halophytes and salt-tolerant plants do not perform well in the establishment phase.
These results can only identify salt as another limiting factor for argan establishment, but
more research may reveal that established and mature trees can overcome saline soil
conditions. If signiﬁcant natural regeneration of argan is not occurring, surface soil
salinization many be another barrier for argan to overcome. While argan may be able to
bypass saline conditions with a deep taproot, neither seeds nor seedlings should be
planted in saline soils.

47

BIBLIOGRAPHY

BIBLIOGRAPHY

Abrol, LP. 1986. Salt-aﬁ‘ected soils: problems and prospects in developing countries. In:
Global Aspects of Food Production, M.S. Swaminathan and SK. Sirnlna (eds),
Tycooly Publishing, Riverton, New Jersey. pp. 283-305.

Abrol, 1.0., 1.8. P. Yadav, and F1. Massoud. 1988. Salt-aﬁ‘ected soils and their
management. FAO Soils Bulletin 39. Food and Agriculture Organization of the
United Nations. Rome. 131p.

Arit; A 1994. Effect of seedling depth on emergence of Argania spinosa (L.) Maire. AI
Awarnia 87:149-153.

Bani-Aameur, F., L. Louali and P. Dupuis. 1998. Maturation et chute des fruits de
l'argarnier. Actes de I'Institut Agronomique et Vétérinaire Hasscm II Waroc).
18(3): 137-144.

Baﬁuls, J. and E. Primo-Millo. 1995. Eﬁ‘ects of salirnity on some Citrus scion-rootstock
combinations. Annals of Botany 76297-102.

Benchekroun, F. and G. Buttoud. 1989. L'arganeraie dans l'économie rurale du Soud
Ouest marocain. Forét Méditerranéenne 2: 127-136.

Bewley, 1D. and M. Black. 1994. Seeds: Physiology of and Germination. 2'II ed. Plenum
Press, New York. 445p.

BOSTID. 1990. Saline agiculture: salt tolerant plants for developing countries. National
Academy Press. Washington, DC. 143p.

Buttoud, G. 1990. Enjuex et limites des legislations ago-forestieres: l’exemple de
l’arganeraie du sud-Marocain. In: Forestry legislation, Report of the IUFRO
Working Party S4.08-03. G. Schmithusen, ed. Zurich. pp. 58-74.

Combating Desertiﬁcation and Desert Rehabilitation. In: Government of Israel’s
Development Option: The Middle East/East Mediterranean Region. Version IV.
[Online] Available http://www.israel.org/peace/projects/chap6.html, August 1995.

Daily, G.C. 1995. Restoring value to the world’s degraded lands. Science 269:350-353.

Elnrig, F .R 1974. Die Arganie. Charakter, Okologie und Wirtschaﬁliche Bedeutung eines
Tertiﬂrreliktes in Marokko. Petermanns Geogr. Mitt. 118: 1 17-125.

El Motaium, R, H. Hu and PH. Brown. 1994. The relative tolerance of six Prunus
rootstocks to boron and salirnity. American Society of Horticultural Science
119(6): 1 169-1 175.

49

El Mourid, M. and M. Karrou. 1996. Agriculture in arid and semi-arid regions of
Morocco: Challenges and prospects. Al Awamia 92:83-91.

Emberger, L. 1955. Une classiﬁcation biogéographique des climats. Rev. Tav. Faculté
. des Sciences Montpellier, Série bot. 723-45.

Fereres, E. 1983. Short and long-term eﬁ‘ects of irrigation of the fertility and productivity
of soils. In: Nutriernt Balances and the need for Fertilizers in Semi-Arid and Arid
Regions. Proceedings of the 1 7th Colloquium of the International Potash
Institute, Rabat and Marrekech, Morocco. pp. 283-304.

Ferradous, A, F. Bani-Aameur and P. Dupuis. 1996. Climat stationnel, phénologie et
ﬁ'uctiﬁcation de l'arganier (Argania spinosa (L.) Skeels). Actes de I’Institut
Agronomique et Vétérinaire Hassan II Maroc). 17(1):51-60.

Gentil, L. 1906. Dans le Bled es-Siba. In: Explorations ou Maroc. Masson (Paris). pp.
341-3 54.

Gutierrez Boenn, F.H., 1D. Scheiner and RS. Lavado. 1994. Some effects of soil salinity
on growth, development and yield of rapeseed (Brassica napus L.). Journal of
Agronomy & Crop Science 172: 182-187.

Janick, J. 1989. Horticulture in Morocco: North Aﬁica’s California. HortScience
24(1): 18-22.

Kaﬂraﬁ, U. and N. Berstein. 1996. Root growth under salinity stress. In: Plant roots: the
hidden half, Y. Waisel, A Eshel, U. Kaﬂraﬁ (eds), 2" ed., Marcel Kekker, Inc,
New York. pp. 435-451.

Khan, M.A and Y. Rizvi. 1994. Eﬁ‘ect of salinity, temperature, and growth regulators on
the germination and early seedling growth of Atiplex gnﬂithii var. stocksii.
Canadian Journal of Botany 72:475-479.

Khan, MA and LA. Ungar. 1998. Seed germination and dormancy of Polygonran
aviculare L. as inﬂuenced by salinity, temperature, and gibberellic acid. Seed
Science & Technology 26:107-117.

Kigel, J. 1995. Seed germination in arid and semiarid regions. In: Seed development and
germination. J. Kigel and G. Galili (eds), Marcel Kekker, Inc., New York. pp.
645-699.

Le Houérou, RN. 1981. Impact of man and his arnimals on mediterranean vegetation. In:
Ecosystems of the World, No. 11 Mediterranean-Type Shrublands. F. di Castri,
D.W. Goodall and RL. Specht, eds. Elsevier, Amsterdam. pp. 479-517.

Maroc Division de la Cartographic. 1994. Maroc Forestier no. 850. Direction de la
Conservation Fonciere, du Cadastre et de la Cartographic, Rabat.

50

Maroc Division de la Cartographic. 1996. Carte de Sols du Maroc. Direction du
Cadastre et de la Cartographic, Rabat.

Maurin, R 1992. L’huile d’Argan Argania spinosa (L.) Skeel SapotaceaezMise au Point.
Revue Francaise des Corps Gras 39(5-6):139-146.

Mazih, A and D. Debouzie. 1996. Infestation rate of argan ﬁuit (Argania .minosa) by
the Mediterrranean ﬁ'uit ﬂy (Ceratitis capitata) in relation to phenology and
maturation of the fruit. Entomologia Erperimentalis et Applicata 81:31-38.

Mellado, J. 1989. 8.0.8. Souss: argan forest destruction in Morocco. Oryx 23:87-93.

Metro, A 1952. Observation préliminaire faites sur l'arganier a l'Oued Cherrate et in Dar
Askraoui en we de selections généalogiques. Ann. Rech. Forest. (Rabat), rapport
annuel 1952:201-215.

Monnier, Y. 1965. Les Problems Actuels de l’Arganeraie Marocaine. Revue Forestiere
Francaise 17(11):750-767.

Montoya, J.M. 1984. El Argan (Argwria qn’nosa(L.) Skeel): Potencial Silvopastoral y de
Repoblacion en Espaﬂa. Anales del Instituto Nacional de Investigaciones Agrarias
(Spain) 8: 141-152.

Morton, IF. and G.L. Voss. 1987. The Argan Tree (Argania sideroxylon, Sapotaceae),
A Desert Source of Edible Oil. Economic Botany 41:221-233.

Nerd, A, E. Eteshola, N.Borowy and Y.Mizrahi. 1994. Growth and Oil Production of
Argan in the Negev Desert of Israel. Industrial Crops and Prodrwts 2:89-95.

Nerd, A, V. Irijimovich and Y. Mizrahi. 1998. Phenology, breeding system and M
development of Argan [Argania spinosa, Sapotaceae] cultivated in Israel.
Economic Botany 52(2): 161-167.

Nouaim, R, R Chaussod, A El Aboudi, C. Schrnabel and JP. Peltier. 1991. L'arganier:
essai de synthese des connaissances sur cet arbre. In: Physiologie des Arbres et
Arbustes en zones arides et senni-arides. Group d'étude de l'arbre (eds). John
Libbey Eurotext, Paris. pp. 373-388.

Nouaim, R and RChaussod. 1994. Mycorrhizal dependency of micropropagated argan
tree (Argania spinosa): 1. Growth and biomass production. Agroforestry systems
27:53-65.

Nouaim, R, M. Lineres, J.-M. Esvan and R Chaussod. 1994. Mycorrhizal dependency
of nnicropropagated argan tree (Argania spinosa): II. Mineral nutrition.
Agroforestry Systems 27:67-77.

51

Prendergast, H.D.V. and CC. Walker. 1992. The Argan: Multipurpose Tree of
Morocco. Ihe Kew Magazine 9:76-85.

Rhoades, JD. 1990. Soil Salinity - Causes and Controls. In: Techniques for Desert
Reclamation. AS. Goudie (ed), John Wiley & Sons, New York. pp. 109-134.

Sasson, A 1993. Biotechnologies in Developing Countries: Present and Future. Vol. 1:
Regional and National Survey. UNESCO Publishing. pp. 629-641.

Singer, M.J. and D.N. Munns. 1991. Soils, an introduction. Second Edition. Macmillan
Publishing Company, New York. 473p.

Swearingern, W.D. 1987. Moroccan Mirages: Agrarian Dreams and Deceptions, 1912-
1986. Princeton University Press. 217p.

Szabolcs, I. 1979. Review of research on salt-aﬂ‘ected soils. UNESCO, France. 137p.
Szabolcs, I 1989. Salt-aﬂ‘ected soils. CRC Press, Inc. Boca Raton, Florida. 274p.

Teclaw, RM. and J. G. Isebrands. 1986. Collection procedures aﬁ‘ect germination of
northern red oak (Quercus rubra L.) acorns. Tree Planter ’s Notes 37(3):8-12.

Tomar, 0.8. and J.S.P. Yadav. 1985. Eﬂ‘ect of saline irrigation and fertilizer application
on growth of tree seedlings. Annals of Arid Zone 24(2):94-100.

Ungar, LA 1995. Seed germination and seed-bank ecology in halophytes. In: Seed
development and germination. J. Kigel and G. Galili (eds), Marcel Kekker, Inc.,
New York. pp. 599-628.

Ungar, IA 1996. Eﬂ‘ect of salinity on seed germination, growth, and ion accumulation
of Atriplex patula (Chenopodiacaea). American Journal of Botany 83(5):604-607.

Wild, A, ed. 1973. Russell's Soil Conditions and Plant Growth. lltln edition. Longnan
Scientiﬁc & Technical and John Wiley & Sons, Inc. New York. 991p.

Zahidi, A and F. Bani-Aameur. 1997. Germination et survie des arnandes de l'arganier
(Argania spinosa (L.) Skeels): eﬂ‘ets de la duree de stockage, de la date semis et
du genotype. Annales de la Recherche Forestiere auMaroc 3022-16.

Zahidi, A and F. Bani-Aameur. 1998. Argan seedling damping-oﬂ‘ under mrrsery

conditions: eﬁ'ects of mother-tree genotype, kernel origin and seedling age.
Ecologia Mediterranea 24:27-32.

52

nrcurcaN STATE UNIV. LIBRARIES
llHI”WilliVIMINIMUM"INlllHMllHlllHlHl
31293020604025