From the Handbook of Energy Crops, unpublished
by James A. Duke
Phoenix
dactylifera L.
Arecacea
Date palm
Uses
Folk
Medicine
Chemistry
Description
Germplasm
Distribution
Ecology
Cultivation
Harvesting
Yields
and Economics
Energy
Biotic
Factors
References
Uses
The Arabs say that there are as
many uses for dates as there are days in the year. Cultivated primarily
for fruit eaten fresh or dried, being a high energy food of high sugar
content, as well as a good source of iron and potassium. A date diet is
low in fats and proteins; hence the Arabs eat them habitually with some
form of milk (Tackholm and Drar, 1973).
Fruits often preserved
by drying or pressing them together into large cakes. Other products
include date honey, made from juice of fresh fruit; date sugar; date
sap, often made into a fermented beverage; date palm flour, made from
pith of tree; the palm heart, eaten as a salad; oil from seeds; the
kernels are ground up or soaked in water for days and used for animal
food; seeds are also strung as beads; both wine and honey are derived
from the date; in medevial days, the palm was thought to prevent
sunstroke, avert lightening, cure fevers, and drive away mice and
fleas. Mats are woven from the leaves, while the fibers provide thread
and rigging for boats. The leaf midribs are used for fencing and
roofing.
There is sap in the palm tree which, after
fermentation, is used as a liquor. Sap, collected in the morning, may
contain 4–5% alcohol by evening. Seed oil used for soap
manufacture. The wood from the trunk is cut into planks, used for
doors, beams, and rafters.
Folk Medicine
Regarded
as aphrodisiac, contraceptive, demulcent, diuretic, emollient,
estrogenic, expectorant, laxative, pectoral, purgative, refrigerant,
the date is listed in folk remedies for ague, anemia, asthma,
bronchitis, cancer, catarrh, chest, condylomata, cough, diarrhea, eyes,
fatigue, fever, flu, gonorrhea, endurations, longevity, piles,
pterygia, splenitis, sterility, stomachache, thirst, toothache,
tuberculosis, urogenital ailments, vaginitis, virility, warts, and
whitlows (Duke and Wain, 1981). Hartwell (1967–1971) mentions
cancers, indurations or tumors of the abdomen, gum, liver, mouth,
parotids, spleen, stomach, testicle, throat, uterus, and viscera.
Medicinally, fresh juice is cooling and laxative; gum useful in
treatment of diarrhea and diseases of gentio-urinary system; fruit is
deculcent, expectorant, anti-scorbutic, nutrient, laxative,
aphrodisiac, and is prescribed in asthma, chest complaints and cough,
fever, and gonorrhea. A plaster of the nuts or of the bark is a folk
remedy for whitlows, hardnesses, and scirrhi. Tackholm and Drar (1973)
report on one "superstition" that may have a scientific rational behind
it. "The pollen of a male date palm mixed with water is a charm against
childlessness. If you consult the chemistry paragraph, you will see
that the pollen contains estrogenic hormones. Egyptians also believe
that to swallow one, two, or three date stones will prevent
child-bearing for many years.
Chemistry
Pollen,
containing cholesterol and estrone, exhibits gonadotrophic activity on
immature rats. Per 100 g, the fruit pulp is reported to contain 317
calories, 15.3 g H2O, 2.5 g protein, 0.4 g fat, 75.8 g carbohydrate,
3.9 g fiber, 2.1 g ash, 120 mg Ca, 50 mg P, 7.3 mg Fe, 26 mg b-carotene
equivalent, 0.01 mg thiamine, 0.02 mg riboflavin, 0.9 mg niacin, and 3
mg ascorbic acid (C.S.I.R., 1948-1976). The Wealth of India also
reports the mineral composition of exotic dried dates 754 mg K/100 g,
68 mg Ca, 58 mg Mg, 1.6 mg Fe, 0.21 mg Cu, 64 mg P, and 51 mg S/100 g.
Zinc, arsenic, and 6.3 mg I/100 g were also reported. On the other
hand, Vandercook et al. (1980) tabulate data of importance to those
interested in higher potassium—lower sodium diet.
|
Inorganic
constituents of dates
(mg/
100 g dry weight)
|
| Element |
Halawy |
Sayer |
| Potassium |
716.0 |
657.0 |
| Sodium |
37.0 |
38.0 |
| Calcium |
65.0 |
97.0 |
| Magnesium |
71.0 |
79.0 |
| Phosphorus |
84.0 |
63.0 |
| Iron |
3.7 |
3.1 |
| Aluminum |
5.1 |
-- |
| Copper |
0.2 |
0.2 |
| Sulfur |
52.0 |
59.0 |
| Manganese |
3.3 |
4.6 |
| Silicon |
66.0 |
66.0 |
| Chlorine |
27.0 |
31.0 |
High
potassium diets recently were shown to retard or prevent the
development of gastric ulcers in experimental rats. According to
Kikuchi and Miki (1978) the sarocarp contains cholesterol, campesterol,
stigmasterol, b-sitosterol, and isofucosterol. The dry date seed
contains 7.9% moisture, 5.2% protein, 6.8% fat, 65.5% carbohydrates,
13.6% fiber, and 0.89% ash. The fatty acid composition of the seed oil
is 8% lauric, 4% myristic, 25% palmitic, 10% stearic, 45% oleic, and
10% linoleic with some capric and caprylic acids as well. Jaggery, made
from the sap of the tree boils down to 9.6% moisture, 86.1%
carbohydrates, 1.5% protein, 0.3% fat, 2.6% minerals, 0.36% Ca, and
0.06% P. Leaves, used for manure, contain 0.4–0.66% N,
0.025–0.062 P, 0.33–0.66 K, and
10.0–16.4% ash. Fruit
stalks contain 0.28–0.42% N, 0.017–0.04% P,
3.46–4.94% K, and 7.7–9.88% ash (C.S.I.R.,
1948–1976). One unexpected compound in date tissue is
serotonin
at levels of 850 mg per 100 g. Acetaldehyde is the major volatile
aldehyde in date. Chlorophyll in Iranian green Shahani dates drops from
410 mg/g fresh date to 0 in ripe brown dates (Vandercook, et al, 1980).
Traces of coumarin occur in the leaves and leaf stalk. Leaves contain
luteolin-7-glucoside, luteolin-7-rutinoside, and glycosylapigenin.
Pollen contains cholesterol and rutin. The hemicellulose of the pollen
contains 46% arabinose, 25% galactose, 18% xylose, 9% rhamnose, and 2%
uronic acid. Seeds contain cholesterol estrones, polysaccharide A (with
10:1 D-mannose:D-galactose) polysaccharide B, and xylose. The fruit
pulp also contains leucanthocyanins, pipecolic acid, 5-oxypipecolic
acid, (C6H11NO3) and the piperidine derivative baikiain (C6H9NO2) as
well as tannin.
Description
Dioecious
tree (rarely monoecious) to 30 m tall. Leaves pinnate, 4–8 m
long, with pointed enduplicate leaflets, with persistent leaf bases and
a terminal crown of 100–120 leaves. Flowers small, white, on
a
richly branched spadix, surrounded by a solitary, large spathe. Calyx
cup-shaped, 3-toothed, petals 3, in female flowers twice as long as the
calyx. Stamens 6 with linear dorsifixed anthers. Ovaries 3, only one
developing into fruit. Fruit usually cylindrical, occasionally rounded
or ovoid, 2.5–7.5 cm long, with fleshy, sugary pericarp,
yellowish to reddish brown (Takholm and Drar, 1973; Purseglove, 1972).
Germplasm
Reported
from the African Center of Diversity, date, or cvs thereof, is reported
to tolerate alkali, drought, frost, heat, heavy soil, high pH, salt,
sand, slope, smog, and waterlogging for brief periods (Duke, 1978).
Barrett (1973) lists the following sources for desirable characters in
a date breeding program:
Table 1. Source of some desirable characters used in the date-breeding
program
| Variety |
Desirable
Characters |
| Abbada |
Attractiveness,
glossy black-fruit with frost-like bloom, midseason maturity. |
| Amir
Hajj |
High
quality, little spoilage of fruit in wet weather. |
| Barhee |
High
quality, heavy yield, late maturity, low tannin in khalal stage. |
| Bedraya |
Large
fruit, firm texture, midseason maturity. |
| Dayri |
High
quality, distinctive rich flavor, moisture tolerance, good size,
semidry texture. |
| Deglet
Beida |
Light-colored
fruit, smooth skin, very firm texture, early maturity. |
| Deglet
Noor |
Superior
quality, distinctive rich flavor, semidry texture, long fruitstalks. |
| Empress |
High
quality, attractiveness, good size, distinctive rich flavor. |
| Halawy |
High
quality, distinctive rich flavor, moisture tolerance, early maturity. |
| Horra |
Good
size, very firm texture, long fruitstalks, midseason maturity. |
| Khadrawy |
High
quality, dwarf stature, moisture tolerance, precocious flowering,
sparse spines, early maturity. |
| Kush
Zebda |
Superior
fruit quality, distinctive rich flavor, long fruitstalks. |
| Medjool |
Large
fruit, moisture tolerance, early maturity, good quality. |
| Tadala |
Large
fruit, moderate moisture tolerance, attractiveness, early maturity. |
| Thoory |
Light-colored
fruit, moderately large fruit, very firm, moisture tolerance, late
maturity. |
Tackholm
and Drar discuss many of the Egyptian cvs. and Knight (1980) some of
the American grown cvs. "Since 1913 the largest collection of date-palm
varieties ever made from the chief growing centres in the East was
tried in Arizona and California...". (2n = 28, 36)
Distribution
Not
known in the wild state, cultivated and subspontaneous throughout the
desert regions between 15° and 35° N, from the Canaries
and
Morocco in the west to India in the east. Recorded from all the inner
and littoral parts of N. Africa, from the southern parts of Balkan
Peninsula and Asia Minor, from Syria, Palestine, Transjordania, Iraq,
Arabia, Iran, Baluchistan. Cultivated as an ornamental in S. Europe,
but seldom matures fruit except in extreme southern parts of Italy and
Spain. Cultivated in Arizona and California, USA, and Queensland,
Australia. There is evidence of date usage 8000 years ago in W. India
as well as its cultivation in Sumeria and the ancient Egyptian empire
(Knight, 1980).
Ecology
Ranging
from Tropical Desert to moist through Warm Temperate Thorn (with mild
frost) to Dry Forest Life Zones, date palm is reported to tolerate
annual precipitation of 3.1 to 40.3 dm (mean of 16 cases = 11.1),
annual temperature of 12.7 to 27.5°C (mean of 16 cases = 22.2),
and
pH of 5.0 to 8.2 (mean of 12 cases = 6.5) (Duke, 1978, 1979). A full
bearing orchard requires the equivalent of 23 dm rainfall (Knight,
1980). Some of the date palm's peculiar ecological whims include: It is
very tolerant of alkali soils and can grow in soils containing
3–4% white alkali; but to bear well, the palm's roots must be
in
a stratum with less than 1% of alkali silts. Grown ideally where the
permanent water table is within of the soil surface. At least 8 to 9
acre feet of irrigation water per year is necessary for good production
on bearing palms. Daytime temperatures of 50°C are tolerated.
For
proper ripening of fruit, the mean temperature between the period of
flowering and ripening should be above 21.2°C rising to
26.7°,
for at least a month. Finest date varieties require 3300 units of heat,
a unit being defined as degree above a daily mean of 64.4°F
between
the flowering, fruit development, and ripening periods. Israelis blame
some of their problems on inability to control the flowering date. (It
takes 6 months for the fruit to ripen.) There can be some control by
withholding irrigation during fall and winter. There must be no rain
during flowering time. An average temperature of 30°C is good
for
proper ripening. Winter temperatures below -8°C (ca
17°F) are
harmful. Any good soil that is not too heavy will do. In clean soil, a
little hard water is OK; in alkaline soil, clean water is OK; but the
combo of alkaline soil and salty water is too much. Dates do well even
where there is a crust of salt on the surface. If in the top
2–2.5 m there is a 30-cm layer or strata with 1% alkalinity,
the
date roots will "find" the strata and flare out there.
Cultivation
Propagated
by seed or off-shoots. Seedlings are first planted in nursery rows and
later transplanted to their permanent location. Sometimes planted
around Aswan, they plant several seedlings in the same hole to insure
the presence of females. Normal healthy trees may produce
10–30
or more offshoots. These will root if their bases are encased in soil.
In Egypt they say it takes 8 years for an offshoot to yield
economically. Elsewhere they are planted ca 9 m apart with one male per
50 or more females. Arabs tend to space them at 5.8 x 5.8 m. Offshoots
are buried firmly up to their maximum diameter, taking care that the
crown remains 10–15 cm above the soil so that irrigation
water
does not touch it. They need protective wrapping or shelter against
cold, heat, and wind. In early stages, manuring is productive and palms
may be intercropped with low crops like barley, pulses, and wheat. When
the palms are taller, apricots, figs, grapes, oranges, peaches,
pomegranates, etc. are intercropped. Pruning of the leaves, artificial
pollination (described in Ur ca 2,300 BC), and thinning of the fruits
also recommended. Pollination is helped along by placing cut portions
of the male flower spikes in the receptive female inflorescence. Recent
breakthroughs in tissue culture propagation (Tisserat, 1979) bode well
for the expansion of date production.
Harvesting
In
Egypt, dates usually flower in February and March, ripening in August
and September. Precocious trees may start fruiting at 2–3
years,
but full crops are not usual until 5–8 years old. Tackholm
and
Drar relate a peculiar type of rejuvenation used with date palm: Old or
damaged trees are rejuvenated by making a horizontal hole 4 m below the
summit. A wooden cylinder is pushed into the hole, and the place
surrounded by earth kept in baskets. Roots are soon produced at this
spot. Later, it is possible to cut off the trunk below the wooden
cylinder and transplant the summit. It will start carrying fruit again.
There are known cases where such operations have been successfully
performed on the same tree 4 times (Tackholm and Drar, 1973). Trees may
bear for a century or more.
Yields and Economics
In
Egypt, palms yield 5–30 bunches, averaging 12, each bunch
containing 5–15 kg dates, suggesting average yields of 120 kg
date/tree/yr (Tackholm and Drar, 1973). According to Duke (1977b), "A
single date palm may yield 120–280 liters of toddy and
40–80 kg of dates, or 7–10 MT of dried dates per
hectare."
World exports averaged around 350,000 MT in 1975. Iraq accounting for
more than 75%, Iran less than 10%. Algeria accounted for ca 3.3%,
Tunisia, 1.4%. During this same period, the US produced more than
20,000 MT (since declined), importing ca 14,000 MT and exporting ca
6,500 MT.
Energy
Yields
as high as 250 kg per tree are recorded in California and Arizona, but
a farmer with 50 kg per tree should be satisfied. Israelis reported
15–66 kg per tree in various experiments. With 125 trees per
ha,
that suggests that yields of 1,000 kg/ha would be considered low and
yields of 5,000 kg/ha high, with 8,000 kg/ha quite high, but
theoretically possible. Natural fruit drop amounts to 25% so thinnings
of 25% are practiced, and the thinnings could be counted among the
residues. The chaff factor of 0.2 accounts for the seed. In Egypt and
the Sudan, the trees are pruned back to 40 or 50 leaves. Excess leaves
may be pulped or treated as biomass. Midribs are sometimes used in
making crates. Annual production of leaves is ca 12–20 per
tree
per year. Offshoots should be pruned, and may constitute a sizeable
residue.
Alcohol may be made by fermenting the sap; a tree
yielding ca 5 liters toddy per day for 6 to 8 weeks (C.S.I.R.,
1948–1976). Alcohol could also be made, of course, from the
sugars. Perhaps optimistically, Samarawira estimates a sucrose
production potential of 7.2 MT/ha/yr, comparing it to the world average
of 6.6 for cane sugar and 5.6 for sugar beet in Europe. Samarawirals
optimistic numbers are derived by multiplying the fruit yield potential
of 12 MT/ha by 60%, the sucrose percentage of the DM of the mesocarp of
the Khalal and early Rutab stages of fruit development. Certainly if
these numbers are real, this has energetic implications for the arid
tropics when the oil runs out (Samarawira, 1983). To me, it looks as
though the date palm should be as productive of biomass as the oil palm
in frost free irrigated situations. Oil palm is reported to have an
annual productivity of 37 MT/ha/yr in Zaire (Duke, 1981b).
Biotic Factors
Ag Handbook 165 lists the following diseases affecting the date palm: Alternaria sp.
(leaf spot), Alternaria
citri (brown spot of fruit), Alternaria stemphylioides
(fruit spoilage), Aspergillus
niger (calyx-end rot), Auerswaldia palmicola
(on leaves), Catenularia
fuliginea (fruit rot), Ceratostomella radicicola
(root rot), Colletotrichum
gloeosporioides (on leaves), Diplodia phoenicum
(leafstalk rot, shoot blight, fruit rot), Endoconidiophora paradoxa
(black scorch, heart bud rot), Fusarium
spp. (inflorescence blight, fruit rot), Graphiola phoenicis
(leaf spot, false smut), Meliola
furcata (black mildew), Meloidogyne spp.
(root knot nematodes), Omphalia
pigmentata (decline disease), Omphalia tralucida
(decline disease), Penicillum
roseum (fruit rot), Pestalotia
sp. (leaf spot), Phomopsis
phoenicola (fruit rot), Phymatotrichum omnivorum
(on roots), Pleospora
herbarum (fruit rot, mold), and Poria
spp. (wood rot). Popenoe (1920) assesses the percent damage caused by
some of the major insect pests. Tackholm and Drar give a good account
of Egyptian diseases and pests.
References
Agriculture Handbook 165. 1960. Index of plant diseases in the United
States. USGPO. Washington.
Barrett, H.C. 1973. Date breeding and improvement in North America.
Fruit. Var. J. 27(3):50–55.
C.S.I.R. (Council of Scientific and Industrial Research).
1948–1976. The wealth of India. 11 vols. New Delhi.
Duke, J.A. 1977b. Palms as energy sources: A solicitation. Principes
21(2):60–62.
Duke,
J.A. 1978. The quest for tolerant germplasm. p. 1–61. In: ASA
Special Symposium 32, Crop tolerance to suboptimal land conditions. Am.
Soc. Agron. Madison, WI.
Duke, J.A. 1979. Ecosystematic data on economic plants. Quart. J. Crude
Drug Res. 17(3–4):91–110.
Duke,
J.A. 1981b. The gene revolution. Paper 1. p. 89–150. In:
Office
of Technology Assessment, Background papers for innovative biological
technologies for lesser developed countries. USGPO. Washington.
Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer
index with more than 85,000 entries. 3 vols.
Hartwell, J.L. 1967–1971. Plants used against cancer. A
survey. Lloydia 30–34.
Kikuchi,
N. and Miki T. 1978. The separation of date (Phoenix dactylifera)
sterols by liquid chromatography. Mikrochimica Acta
1(1/2):89–96.
Knight,
R., Jr. 1980. Origin and world importance of tropical and subtropical
fruit crops. p. 1–120. In: Nagy, S. and Shaw, P.E. (eds.),
Tropical and subtropical fruits. AVI, Westport, CT.
Purseglove, J.W. 1972. Tropical crops. Monocotyledons 2. John Wiley
& Sons, New York.
Samarawira, I. 1983. Date palm Phoenix
dactylifera. Potential source for refined sugar. Econ.
Bot. 37(2):181–186.
Tackholm, V. and Drar, M. 1973. Flora of Egypt. vol. II. Otto Koeltz
Antiquariat. Reprint. Originally published 1950.
Tisserat, B.H. 1979. Tissue culture of the date palm. J. Hered.
70:221–2.
Vandercook,
C.E., Hasegawa, S., and Maier, V.P. 1980. Dates. p. 506–541.
In:
Nagy, S and Shaw, P.E. (eds.), Tropical and subtropical fruits. AVI
Westport, CT.
Last update Wednesday, January 7, 1998 by aw
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