Anatomical observations regarding the stem of the date palm (Phoenix dactylifera L.) used for
construction purposes
Bernabei Mauro*, Zimbalatti Giuseppe**, Proto Andrea Rosario**
*Trees and Timber Institute - IVALSA/CNR, Italy – 38010 San Michele a/A (TN)
** Department of Agroforestry and Environmental Sciences and Technologies Mediterranean University of
Reggio Calabria, Italy
corresponding author: bernabei@ivalsa.cnr.it
Mauro Bernabei
Laboratorio di Dendrocronologia
IVALSA/CNR, http://www.ivalsa.cnr.it/dendrocrono.htm
via Biasi 75 - 38010 S. Michele all'Adige (Trento, Italy)
tel. 0461/660207, fax 0461/650045
Abstract
Phoenix dactylifera L. is a dioecious species, belonging to the monocotyledons (Class: Liliopsida). The date
palm is well-known for its fruit production, the dates, which are the reason for the widespread distribution
of this tree and for the creation of numerous cultivars with different characteristics. In this study, four date
palm cultivars were investigated, using anatomical analysis: Ammari, Deglet, Thoory and Ftimi. The
material examined had originally been used for construction purposes and differed in age. The estimated
age of the artefacts from which the samples were taken ranges from ten to 100 and 200 years. The results
of the analyses have shown that the principal cause of decay for palms are fungi. There is a positive
relationship between the age of the sample material and cellular decay, caused by the presence of hyphae.
Various reproductive elements, such as spores and conidia, were also abundant. Generally, there were few
signs of attack by wood-eating insects. The older wood (100 and 200-year-old) was characterized by a
reduction in the parenchymatous matrix surrounding the vascular bundles. As a consequence, the bundles
separate one from another, a process which lends old palm “wood” its typical fibrous aspect.
Key word: date palm, Phoenix dactylifera, cultivar, anatomical characterization, decay.
Introduction
Phoenix dactylifera L. is a dioecious species belonging to the monocotyledons (Class: Liliopsida). The date
palm is well-known for its fruit, the dates, which are the reason for the widespread distribution of this tree
and the creation of numerous cultivars with different characteristics. Palm cultivation represents the main
source of earnings in many middle eastern countries (Zaid, 2001), where the total area dedicated to this
production exceeds 175,000 ha (FAO, 2002).
The date palm is native to the desert regions of North Africa and the middle east. Known since ancient
times, the palm was considered a symbol of fertility by the Egyptians; it was represented by the
Carthaginians on their coins and used by Greeks and Romans as an ornament for celebrating victory.
Date palm leaves were an important secondary product obtained from the tree’s cultivation. Leaves were
used to plait baskets and other articles; the fibre extracted from the leaves was used to make ropes and
string; whereas the material obtained from the stem, wrongly called “wood”, was used to construct
buildings, including some of great cultural interest.
Although, in comparison with “real” wood, date palm “wood” has inferior physical-mechanical
characteristics, in the past it was employed over the entire Sahel zone. It is still used today, especially in the
reconstruction and restoration of historical buildings or country houses. In the past, it was employed in the
construction of country buildings, the roofs of houses and places of work, where its good thermal insulation
properties were particularly appreciated.
Palm “wood” and its leaves were also used for roofing the lanes in Moroccan, Tunisian (Fig. 1) and Iranian
towns (El-Mously, 2001).
Palm wood is rarely used in the main structure of buildings, it is often employed for making small beams or
other wooden elements of a secondary nature. However, palm wood sometimes has an important
aesthetic and ornamental function. This is the case in many buildings in Mali, such as the Great Mosque of
Djenné (Fig. 2).
The walls of the Great Mosque are made of mud bricks, baked by the sun and covered with mud plaster,
which give the surface its typical smooth, plastic aspect. Sheaves of small palm-wood beams, 6-8 elements
per sheaf, spaced out at regular 60cm-intervals, decorate the building. The sheaves also serve as scaffolding
during the mosque’s periodic restoration (Fig. 3). The historic city centre of Djenné, including the Great
Mosque, was designated a World Heritage Site by Unesco in 1988.
Other important examples of this kind of architecture are the Great Mosque of Timbuktu and the Palace of
the Sultanate of Zinder, in Niger.
This kind of African architecture and its traditional building techniques have recently been commended by
ICCROM (Sidi & Joffroy, 2005), the International Centre for the Study of the Preservation and Restoration of
Cultural Property, established by UNESCO in order to promote the conservation and restoration of
monuments and sites of archeological, artistical and historical interest.
Although palm wood is widely employed in historical buildings, we do not know much about the material’s
performance in time, as studies on palm anatomy are not numerous (Tomlinson, 1990).
The objectives of this work are:

to evaluate possible anatomical differences among the tested cultivars;

to analyze the process of decay affecting sawn palm wood over a period of time;

to determine the principal factors of decay in machine-cut material; and

to find out if there are any differences in the resistance to decay among cultivars.
An outline of the anatomy of the date palm stem
The date palm stem is made up of vascular bundles (Arrigoni, 1973) inserted in a parenchymatous matrix
(Fig. 4). The vascular bundles are generally composed of 2 or 3 metaxylematic vessels; the relative
phloematic portion develops in proximity to the point of contact between the two vessels, on both sides.
The phloem-xylem system occupies only a marginal portion of the bundle, a considerable part of which is
made up of fibres that wrap the conducting elements like a sheath, thereby increasing the robustness of
the bundle. The fibrous sheath, which is more or less abundant, develops irregularly within the bundles
whose major axis, observed in transverse section, appears to be orientated in an apparently fortuitous
direction (Figs. 4 and 6).
The consequence of this cellular arrangement is the lack of any three-dimensional cellular structure, which
is found in real wood, with its transverse, radial longitudinal and tangential longitudinal sections. In palms,
the planes of observation are limited to transverse and longitudinal sections.
The girth growth of palm trunks is not due to cambial activity, as is the case with trees (secondary growth),
hence it is not connected to the tree’s age. Palm trunks grow as a consequence of the division and increase
of parenchymatous cells. This kind of growth is called “diffuse secondary growth” (Esau, 1977). Therefore,
palms cannot be dated like other trees.
As it is difficult to establish the age of the material, there are no present studies on the relationship
between palm “wood” and the age of the manufactured article. However, this is a matter of great interest,
considering the frequent archaeological discoveries in desert and semi-desert areas.
Materials and methods
Four date palm cultivars were investigated: Ammari, Deglet, Thoory and Ftimi, all coming from the oasis
city of Nefta, region of Tozeur, in the south-west of Tunisia. The material, of various ages, was supplied by
the University of Tunisi. The estimated age of the manufactured goods ranges from modern (10 years) to
100 and 200 years.
The samples consist of 50cm long strips (Fig. 5), two for each cultivar and for each supposed age (Table 1).
Many anatomical observations were carried out on the strips, each of which was cut into a minimum of 10
sections. As mentioned above, the date palm is a dioecious species. In fact, the plant’s gender is easily
visible in a standing tree. It is, however, not possible to determine the gender of samples obtained from the
stem. For this reason, differences due to gender were not taken into consideration in this study.
A transmitted light optical microscope (Olympus CX 41, with magnification 40X, 100X and 400X) was used.
Digital images were acquired.
Quantitative analyses were carried out in conformity with the methodology and terminology reported by
the IAWA Committee (1989). The Image Tool programme was used for measuring the cellular elements.
Results
Quantitative analysis of anatomical elements among cultivars
Table 2 reports the measurements of three anatomical elements (i.e. vascular bundle frequency, bundle
diameter and vessel diameter) of the four date palm cultivars.
As far as the relationship between the anatomical elements is concerned, the frequency of bundles is
inversely proportional to their diameter (r = - 0,86), whereas bigger vessels correspond to bigger bundles (r
= 0,76).
Rate of decay with passing time
Within samples of the same palm cultivar, the amount of decay increases with the sample’s age (Fig. 6). In
particular, the parenchymatous matrix in the youngest samples is still substantial and coherent, which
includes the vascular bundles and a vessel lumen that is always free from possible agents of decay. With
increasing age, the parenchymatous matrix tends to deteriorate until it disappears completely. In 200-yearold samples it is absent. The vascular vessels appear incoherent and often the vessel walls are partially
eroded.
Decay agents
The most important agents of decay are fungi, which are notable in many forms: hyphae among the cells, in
both vessels and parenchyma, spores, conidia and so on (Fig. 6).
Fungi are the principal cause of decay in the parenchymatous matrix. On the other hand, there are very few
signs of insect attack. There is another important alteration on the external surface of the samples, which
indicates that the decay is due to abiotic agents, such as ultra-violet rays and other atmospheric agents.
Discussion and conclusions
The average values variation of the vessels diameter, the diameter of the vascular bundles and their
frequency per mm2 is higher in a same cultivar rather than among the cultivars (Table 2). The test F on the
variation analysis corroborates this observation. So there are not differences which allow to distinguish the
four cultivars from an anatomical point of view. The possible differences are likely to be due to many
causes, as, for example, a different location of the sample inside the palm trunk: more or less internal,
higher or not so high from the ground.
It is interesting to stress that only in the cultivar Ftimi some perforations have been observed (Fig. 7), while
there is an important difference as regards the composition (with a colour varying from red to black) and
the quantity of compounds, contained in the parenchymatous cells.
From an anatomical point of view, the direct relation between the dimension of the vascular bundles and
the average width of the vessels is very interesting (r = 0,76, p < 0,05). Although the vessels component in
the bundles is rather small (about 20% on average), greater vessels generally correspond to greater
bundles.
Usually elder wood (100 and 200 years) is characterized by a rarefaction of the parenchymatous matrix
which surrounds the vascular bundles. As a consequence there is the separation of the bundles one from
another, a process which gives old palm “wood” its typical fibrous aspect. Together with the
parenchymatous matrix decay there is also a general impoverishment of the bundles cellular walls, in
relation to fungi attack which is often very strong.
Just as it happens for wood, fungi are the principal cause of decay. There is a positive relation between the
age of the material and the cellular decay caused by the presence of hyphae. Various reproductive
elements such as spores and conidia, are abundant. It is also evident the action of the abiotic elements, as
the luminous radiation, which have acted with a gradient from the outside to the inside of the single
elements. On the contrary there are few signs of attacks by wood-eating insect.
The use of palm wood in structures of historical interest as the Great Mosque of Djenné or Timbuctu is
often combined with other material liable to deteriorate: mud, wood, stones (Sidi and Joffroy, 2005). The
action of these biotic and abiotic decay agents on these elements is often ravaging. Suffice it to think of
precipitations - light but often very strong- which erode the building.
The action of the rain, besides breaking the material up, makes the environmental conditions fit for fungi
attack which quickly destroy the biological material such as the palm “wood”.
This is the reason why the buildings which traditionally employ the date palm trunk undergo little and
frequent restoration works. As a consequence, even if these buildings are very ancient, they are often
completely rebuilt.
References
Arrigoni O., 1973 - Elementi di Biologia Vegetale. CEA - Casa Editrice Ambrosiana. Milano.
El-Mously H., 2001 - The industrial use of the date palm residues: an eloquent example of sustainable
development. IIth International Conference on Date Palms, Al-Ain, United Arab Emirates. 866-886.
Esau K. 1977 - Anatomy of Seed Plants. 2nd ed. John Wiley and Sons, New York, Santa Barbara, London,
Sydney, Toronto.
FAO, 2002. Date Palm Cultivation. FAO Plant Production and Protection Division. Rome.
IAWA Committee, 1989. List of microscopic features for hardwood identification. IAWA Bull. n.s. 10, 219–
329.
Sidi A. O., Joffroy T., 2005. The conservation of the Grand Mosques of Timbuktu. In: Traditional
conservation practices in Africa. ICCROM, Conservation Studies 2. edited by Thierry Joffroy.
Tomlinson, P.B. 1990. The structural biology of palms. Clarendon Press, Oxford.
Zaid A., 2001. The world date production: a challenging case study. IIth International Conference on Date
Palms, Al-Ain, United Arab Emirates; 902-915.
Fig. 1: Typical use of palm wood as roofing material in North Africa.
Fig. 2: The Great Mosque of Djenné, Mali.
Fig. 3: Restoration of the Great Mosque of Djenné. Palm wood bundles are used as scaffolding.
Fig. 4: Palm wood under a stereo‐microscope. Transversal (left) and longitudinal section (right).
Fig. 5: The material.
Fig. 6: Cultivar Ftimi. In the top row the material is more recent, in the bottom row it is about 200 years
old.
Fig. 7: Scalariform perforation plate in the Ftimi cultivar.