Sandalwood and the sandalwood oil industry is one of the oldest fragrances in the world of perfumes. It has been traded for its fragrant wood and essential oil. Since Indian sandalwood oil can blend well with most of the natural essential oils, it is in great demand in the perfumer industries. Synthetic substitutes have been produced as early as 1960, but are in no way identical to that of the natural material, that it could be replaced in the perfumery industry.
New sandalwood based industries have evolved after 1990 using greater amounts of natural sandalwood oil, hence there was over exploitation of this species in the world, consequently its production and availability is on the decline. The essential oil and allied industries have been using more than 5,000 tons of sandalwood annually.
The genus ‘Santalum’ grows naturally throughout the Pacific and Eastern Indian Ocean regions. Sandalwood tress are evergreen ranging in size from tall shrubs to large trees. They grow in a variety of climates ranging from Australian desert to sub-tropical New Caledonia and at elevations from sea level to 1800 meters. It is distributed in peninsular India, parts of Malaysia, Australia, New Zealand and Polynesia extending to the Hawaiian Archipelago and Juan Fernandez Islands. The species belonging to this genus are usually partial root parasitic plants, equipped with special structures (hostoria) on its root that penetrate the roots of host plants to obtain nutrients.
Some of the species furnish fragrant heartwood, known as sandalwood, yielding different kinds of sandalwood oil.
Sandalwood is the fragrant heartwood of some species of genus Santalum (Santalacease). All the sandalwood oil or fragrant wood traded in international market comes from species in the genus Santalum (Family Santalaceae). The genera contain 16 recognized species, and more than 12 varieties, distributed throughout the world. Out of them only few species, produce commercially exploitable scented heartwood (S. album, S. yasi, S. spicatum, S. austrocaledonicum, S. lanceolatum, S. ellipticum and S. paniculatum). These species are important for their fragrant scented heartwood and for essential oil. Other species of Santalum also produce fragrant heartwood and oil; however their contribution to essential oil industry is limited. Sandalwood wood is also an excellent material for carving and to make curious handicrafts.
All species occur in natural forest in different habitats. Most of the species are over exploited and are under threat as endangered species. The demand for the scented heartwood and natural sandalwood oil is increasing and the supply is on the decline. Because of inconsistent supply, the prices have gone up very steeply depriving its use in various industries. They only alternate is to produce sandalwood commercially with high input and management technique to make a short-term rotation crop.
The genus represented by Santalum album Linn. Produce rich scented heartwood and oil. Its wood is known commercially as “East Indian sandalwood” and the distilled essential oil from it as “East Indian Sandalwood Oil” Sandalwood oil in one of the oldest perfumery materials and commercially important. Both wood and oil are used in incense, jaw-sticks, perfumes, soaps and in medicine. Sandalwood is one of the finest woods for carving, since it is closely grained with fewer knots. It is used for making idols, boxes and other curios of exquisite beauty. Wood and oil of S.yasi is almost similar to that of S.album
@ S.spicatum, popularly known as West Australian sandalwood is also one of the important species producing scented heartwood and oil. Wood has been exported to different countries since 1844. The oil has different chemical composition and better medicinal properties. It is used in perfumery, incense sticks, soaps, toiletries and aromatherapy. Wood is also used for carving. Recently it has become an alternate source for essential oil for sandalwood based industries.
S. lanceolatum is second major type of sandalwood native to Australia; the heartwood contains fewer odors, heartwood yield comparatively less oil; mixes well with other sandalwood oil. The scented oil used in perfumery industry.
@ S.accuminatum is also a native species of Australia and the trees are cultivated for fruits rather than oil.
@ S. austrocaledonicum, is an important species growing in New Calednia and Vanuatu islands, scented heartwood is used for making beautiful handicraft items and the oil produced from heartwood is highly scented and is sold as New Caledonian oil or New Caledonian sandalwood oil. The oil is highly priced and very much sought after in the perfume industries.
@ S.yasi grows in Fiji and in Tonga islands, its scented heartwood yield high quality sandalwood oil, equivalent to Indian sandalwood.
@ S.ellipticum and S.paniculaturm grows in Hawaii Islands, scented oil is used in perfumery industry.
@ Santalum macgregori, called the Papua New Guinea sandalwood is another species producing scented heartwood and oil used in perfumery.
@ Several non-Santalum species (e.g. Osyris tenuifolia, O.laceolata from East Africa and Amyris balsamifera L.from West Indies) are also used as sources of “Sandalwood” type. The less fragrant wood and the distilled oil are different when compared to true sandalwood.
The sandalwood has good history behind and is more culturally attached to different religions, and the products derived from it have been in use for several centuries. Other species of “Santalum” are only of academic interest since their production and contribution to the essential oil industry is limited; however, they are the important species of the region contributing to the cultural heritage and use. Many species are endemic to the region and have not been tried to be introduced into different geographical zones for their performance. Because of over exploitation of the species, many have disappeared are in the endangered list.
There are more than 56 species and varieties of ‘Santalum’ mentioned in the literature, based on the morphological characters.
Different species (Var) of Santalum occurring in the world
| 1. | Santalum acuminatum | 29. | Santalum acuminatum |
| 2. | Santalum album | 30. | Santalum angustifolium |
| 3. | Santalum austrocaledonicum | 31. | Santalum boninense |
| 4. | Santalum cognatum | 32. | Santalum crassifolium |
| 5. | Santalum cunninghamii | 33. | Santalum ellipticum |
| 6. | Santalum cygnorum | 34. | Santalum haleakalae |
| 7. | Santalum diversifolium | 35. | Santalum hornei |
| 8. | Santalum freycinetianum | 36. | Santalum lanaiense |
| 9. | Santalum homei | 37. | Santalum leptocladum |
| 10. | Santalum involutum | 38. | Santalum macgregorii |
| 11. | Santalum latifolium | 39. | Santalum margaretae |
| 12. | Santalum longifolium | 40. | Santalum mitchellii |
| 13. | Santalum marchionense | 41. | Santalum myrtifolium |
| 14. | Santalum mida | 42. | Santalum ovatum |
| 15. | Santalum murrayanum | 43. | Santalum persicarium |
| 16. | Santalum obtusifolium | 44. | Santalum preissianum |
| 17. | Santalum papuanum | 45. | Santalum salicifolium |
| 18. | Santalum preissii | 46. | Santalum yasi |
| 19. | Santalum raiateense | 47. | Santalum affine |
| 20. | Santalum venosum | 48. | Santalum capense |
| 21. | Santalum cuneatum | 49. | Santalum densiflorum |
| 22. | Santalum fernandezianum | 50. | Santalum hendersonense |
| 23. | Santalum insulare | 51. | Santalum lanceolatum |
| 24. | Santalum littorale | 52. | Santalum majus |
| 25. | Santalum megacarpum | 53. | Santalum multiflorum |
| 26. | Santalum oblongatum | 54. | Santalum paniculatum |
| 27. | Santalum pelgeri | 55. | Santalum pyrularium |
| 28. | Santalum spicatum | 56. | Santalum obstfolium |
However, currently only 16 recognized species have been identified in ‘Santalum’ and their geographical occurrences in the world are as follows.
Different species of Sandalwood
Species and varieties Geographical occurrence
S.Album L India, Sri Lanka, Indonesia,
Australia
S. austrocaledonicum Viell New Caledonia, Vanuatu
S.boninense (Nakari) Tuyama Bonin Islands
S.lanceolatum R.Br. Australia
S.macgregorii F. Muell Papua New Guinea
S.Obtusifolium R.Br. Australia
S.yasi. Seem Fiji, Tonga
S.freycinetianum Gaudich Hawaii Islands (O’ahu.Moloka’l)
S.haleakale. Hillebr Hawaiian Island (Maul)
S.ellipticum Gaudich. Hawaiian Island
S.paniculatum Hook & AM. Hawaii Island
S.fernaandezianum F. Phil. Jaun Fernandez Island
S.insulare Bertero Society Islands (Tahiti)
S.acuminatum (R.Br.) A.D.C. Australia
S.murrayanum (T.Mitch) C.A. Gardner Australia
S.spicatum (R.Br.) A.D.C. Australia
History
Santalum ablbum is commercially known as “East Indian sandalwood” and the essential oil distilled from fragrant heartwood is the “East Indian Sandalwood oil”. It has been recognized as one of the oldest perfumery material for several centuries.
“Chandana” is the Sanskrit name ascribed to S.album. The name has been used in India for thousands of years and is frequently mentioned in the ancient Sanskrit literature, some of which predates to Christian era; while sandalwood in Timor has been mentioned before the intervention of colonial interests. Sandalwood in different languages are called.
Sanskrit : Chandana, Sri Ghanda, Krishna Chandana, Srikanda, Peethachandana.
Hindi : Chandan, Chandal, Sandal, Safaid Chandan.
Kannada : Sri Ghanda
Telugu : Chandanum, Chandana Chettu.
Tamil : Sri Ghandam Sandanam.
Gujarat : Sukesh
Bengali : Chandan, Petthachandon
Greek : Svtador, Santalon
French : Santal
English : Sandal
Sanskrit synonyms for sandalwood
Chandana, Gandhasara, Malayaja, Srikanda, Bhadrashri, Chandrayuti, Gandharajam.
Meanings:
Chandana – Chandati ahladasya iiti – pleasant to see
Ghandasara – Gandhasara asya – Aroma is situated in heartwood
Malayaja – Malaye pradeshe jata – Grows in Malaya region
Srikhanda – Shriya utani khandany asya – which is very beautifully good.
Bhadrashri – Barrashri shoba asya – pleasant and auspicious
Chandrayuti – Chandra Jyosna vada ahaladakam – Cooling and pleasant to see, like a moon.
Gandharajam – Gandha dravyanam raja shrestatham – best among all aromatic substances.
Indian sandalwood incense is perhaps the oldest known type of incense used for over 4000 years; Treaties of loud hymns, Rig Veda, and singing hymns of Sama Veda do not make direct evidence to sandalwood. But during the period of Yajur Veda, for havan’s (sacrificial fires), many aromatic and oily plant parts were sacrificed including sandalwood.
Samhitha period (era epic) starts from B.C. 600; In Bhagavatha purana, in the appreciation hymns of Lord Krishna (Krishna ashtothra); we find chants like ‘Kubja Gandha anuliptanga mayee parana poorusshha’ Krishna and Balarama on their way to Kamsa’s palace comes across a dwarf woman (Kubja) who is carrying the fragrant substances to king Kamsa, she gives sandalwood paste to these divine brothers. After applying the sandalwood paste, Lord Krishna blessed the dwarf lady and she became a beautiful woman. The hymns, magical incantations of Vedic age are continued in the societies. Incense was a part of these ceremonial events.
Susrutha Samitha (B.C.150) a great text on Indian wisdom on surgical procedures, equally preferred sandalwood for the management of wounds. There are much more citations available in Indian literature to claim sandalwood are indigenous.
It is believed that Chinese in their sacred temple used fragrant wood to make idols and also built numbers of ancient temples out of sandalwood. Sandalwood incense has been used by many cultures; by the Chinese, it was used in religious ceremonies and many of their deities are made from this beautiful fragrant wood, ancient Egyptian not only used for religious purposes, but also for embalming mummies and for medicinal purposes. It has been reported that sandalwood oil has been used by Sri Lankans (Ceylon) for embalming dead bodies during early 9th century.
Herbalists believe that the incense helps to promote an atmosphere of open-mindedness, peace and spiritual awareness. It is used in the death ceremonies of many cultures. Hindus use as a cleansing agent for the sins; Muslim use sandalwood during burial in order to ensure a quick ascent of the soul to heaven. The Hindu temples, Catholic Churuch, and Jewsih Synagogues are just a few among the many religions that the sandalwood incense.
Folklore and Myth.
Both Indians and Egyptians used cosmetics to preserve youth and beauty of woman. Burmese woman sprinkle a mixture of water and sandalwood oil on people in the street, on the last day of the year, to wash away the sins of the previous years. Queen Elizabeth-1, liked her bed line to be perfumed with sandalwood. Sandalwood is aided in the conjuring of spirits forth from the outer world. It was also said to help soothe those who felt bitter or jealous. Pregnant woman would lay cloths beneath the tree in order to catch the leaves, which were believed to assure any easy birthing process. In olden days sandalwood oil was used as perfume and was limited to Royal families. (Zodiac signs Astrology and plants-find your fate.com)
It has been recorded that Saldin (Europe was the first person to distill sandalwood oil as early as 1488. However, it was Watson and Sudburough (1918) of the Indian Institute of Science, Bangalore, who developed a technique for manufacturing the pharmaceutical quality of sandalwood oil acceptable to European buyers; Pharmacy was the main application of sandalwood oil in the those days. First sandalwood oil factory was established in Indian in 1917 at Mysore.
Origin of sandalwood
It is generally accepted that sandalwood is indigenous to peninsular India. But some believes that it was introduced to India because of its gregarious habit and great adaptability to different climatic zones.
There are references of sandalwood in Indian Mythology, folklore and ancient scriptures.
India and Indonesia both claim that S.album is an indigenous species of their countries and both the countries have strong cultural and historical evidence to support the claims.
Recent research report based on DNA studies (Danica 2004) reveals that Indian sandalwood (Santalum album. L), has taken origin from Queens land of Australia and two independent races moved to India and Indonesia. In my view, this is questionable.
DISTRIBUTION
Santalum album Linn is distributed between 30° N and 40° S from Indonesia in the West to Juan Fernandez Islands in the East and from the Hawaiian Archipelago the North to New Zealand in the South.
In India, it is found distributed all over the country and more than 70% is found in the southern states of Karnataka, Tamilnadu and Kerala. Other states where sandalwood trees are found are, Andhra Pradesh, Kerala, Maharashtra, Madhya Pradesh, Orissa, Rajasthan Uttar Pradesh, Bihar and Manipur. It has now been introduced to many parts of India where it was not naturally distributed. Sandalwood has no definite geographical boundary, it can adapt well into new environments.
In Indonesia, Santalum album occurs on the neighboring islands of Timor, Sumba Flores, Alor and Roti. In Sri Lanka, it is distributed in the southern and central provinces. Occurrence of sandalwood has been reported in Malaysia and Hawaii.
Sandalwood trees have been introduced to Australia, China (Guangzhou province) and Africa (Tanzania and Ghana) in recent years and they have adapted well to the new environment.
Samoa, Tonga Islands are planting S.album under Agro forestry and Tree planting program of minimum of 10 ha per year since 2012. In New Caledonia and Vanuatu, S. album has been introduced, keeping the view of competitive hybrid with S.austrocaledonicum..
In Fiji and Tonga Island S.album hybrids with the local S.yasi, have been widely planted throughout Archipelago. In the humid parts of Fiji, the F1 hybrid performs much better than either parent. Unfortunaly, S.album has been introduced to many Pacific countries for the establishment of plantations; the problem is that it crosses very rapidly with indigenous sandalwood of those regions. Besides loosing unique tree types, the market is going to be very confused when the trees are commercially harvested.
Habit
Santalum album is a small evergreen three attaining a height of 12 to 15 meters and a girth of 1 to 2.4 meters, with slender drooping as well as erect branching. It grows well under partical shade in the early stages but shows intolerance to heavy overhead shade in the middle and late stages of its growth. However, under plantation management with higher moisture levels and donor hosts, the trees have proven to grow exceptionally well. It has dense foliage capable of stopping the wind velocity and survives well along with other tree crops.
The tree flourishes well in altitudes from sea level up to 1800 m above mean sea level growing in different types of soil differing in fertility. Generally, in the wild, it is believed that trees growing on stony or gravelly soils are known to have more highly scented wood; however, in plantation grown sandalwood, the induction of stress during the growing period showed an increase in production of scented heartwood. Santalum album flourishes well where there is moderate rainfall of 600 to 1600 mm. Sometimes sandalwood is found growing in gardens, where rainfall may be as high as 2500 mm, or more. While it grows well in cool climates with long periods of dry weather, it also adapts well to different climatic conditions except water logged or very cold regions. Saline and calcareous soil may not be congenial for sandalwood growth. It can grow in all tropical regions and in situations. lime 0°C to 45°C.
In general, sandalwood tree flourishes in regions where the climate remains cool with a moderate rainfall, much sunshine and long periods of dry weather.
It is a partial root parasite, it can be commercially cultivated in different regions as it adapts well to the new environment.
Tree with different shapes and crown are noticed, conical crown shape, usually have dense dark lush green foliage, Trees are normally erect, but trees show pendulous branching with less foliage. the leaves are with undulating margins are yellowish green or brownish green in colour. The branches and leaves show dropping appearance.
MORPHOLOGY
Sandalwood trees are evergreen and rarely show deciduous nature. In its natural condition it is found associated with different hosts. In the agro- plantations it is found growing with an intermediate and a long term host. The shape of the trees vary depending on the crown; either, conical or globose. These also depend on the self or the artificial pruning.
Bark in initially smooth and dark brown, as the tree grows the splitting of the bark occurs, which is often referred to as crocodile bark.
Leaf
Several leaf types are found in sandalwood (kulkarni and Srimathi 1990.) Most conspicuous among them are copper coloured plants. These are associated with linear and lanceolate leaved types. Variations in the colour of leaves ranging from bluish/greenish yellow to green are also seen in natural condition.
The leaf is dorsiventral; both the surfaces are covered with thick waxy cuticle. Leaf margin is entire, sometimes wavy.
Leaves are opposite and decussate, sometimes show whorled arrangement, having three leaves from internodes. The shape of the leaf can vary significantly and six morphological types have been recognized, they are : ovate, lanceolate, elliptic, linier, big and small (Kulkarni and Srimathi 1982).
A study of the isoenzyme pattern in respect of peroxidase, malate dehydrogenase and esterase in ovate, lanceolate, linear and elliptic shaped leaveys showed characteristic difference at vegetative as well as flowering stages; whereas the big and small leaved morphological types did not show difference in their isoenzyme pattern (Parthsarthiet.al 1985). Based on the above studies it can be deduced that different polymorphic types of S.album exists in nature.
Maturation of leaf from its inception takes three months (Kulkarni and Muniyamma 1998). Leaf initiation starts in most of the trees between February and March. In few trees, leaf formation was also seen in April-May. Shedding of leaves starts in November and continues until April-May in India.
Leaf anatomy
The leaf is dorsiventral; it has clearly distinguishable palisade and spongy parenchyma. The epidermis is single layered on both the surfaces and is covered with a thick cuticle on outside. Cells of the adaxial (upper) epidermis are narrow and tangentially elongated, and without stomata while those of abaxial (lower) side are palpillose showing stomata. The latter are of the “rubiaceous” type. Here the guard cells and subsidiary cells are parallel to each other.
A single hypodermal layer is present on the upper surface. The cells are thin-walled and contain chloroplasts. The cells of mesophy11 possess abundant chloroplasts. Collenchymatous cells are present below the midrib. The cells are polygonal and devoid of any chloroplasts. Some cells containing calcium oxalate crystals and are present in the lamina as well as in the midrib region.
There are three vascular bundles in midrib of a young leaf. Cross section of the older leaves (Fig.5) however, show that secondary growth has taken place in this region and the bundles have joined to form a single structure which appears to be arc-shaped.
Stem
The stem is initially green and tender, then gradually turns brownish and becomes hard. The bark is reddish brown or dark brown and red inside. The stem is smooth in young trees; it turns rough and develops deep vertical cracks, (crocodile bark) as the tree gets older. Based on the characteristics of the bark it is easy to predict the presence of scented heartwood in the standing trees. Some foresters call this as a mature tree, which is incorrect. The young stem is more or les oval; the epidermis is papilose and has an external covering of thin cuticle. There is no endodermis.
In a cross section of stem wood, the outer most cover is the bark and next to it is the white wood or sapwood, the sapwood is white or pale yellow and sharply demarcated to brown or yellow heartwood. Heartwood is hard, close grained, yellowish heartwood is strongly scented compared to brown heartwood Sometimes based on the bark colour and texture, quality of scented heartwood can be determined. Growth rings can be distinguished with the help of a hand lens during the early stages of growth; however, the age of the tree cannot be accurately determined by counting rings as the rings overlap and lie very close to each other.
Stemwood generally is diffuse porous. Growth rings are inconspicuous, delimited by thick-walled latewood fibers. Vessels are very small, larger in the inner side of the growth ring, demarcating the boundary. They are circular or oval in shape, thick walled almost uniformly distributed with the fibrous tissue (Gupta, 1977). The end walls of vessels contain simple perforation while thin lateral walls and those of tracheids are provided with circular borders with included pits. Vessels of primary xylem have helically thickened lateral walls and simple perforated end walls. Both uniseriate and biseriate rays of heterogeneous types are commonly noticed. Occasionally multiseriate rays have also been observed and cells of these rays are lignified.
The primary phloem is not discernable and secondary phloem is comparatively less than primary xylem. In the early formed secondary phloem alternate bands of degenerated cells which form the sieve tube elements are clearly distinguishable. These degenerating phloem cells later become lignified, leaving a very hollow lumen.
Root
The primary root is moderately long and delicate, lateral roots are small in number; fibrous and delicate distributed down the main root. Roots at an early stage develop nodular growth, the first sign of haustoria. However, Nagaveni and Srimathi (1985) have observed that a small number of sandal plants do exist without haustorial nodules even up to the age of two years.
The primary root is distinctly diarch, open and exarch. The secondary growth is profuse. The secondary xylem formed, lie in close proximity to that of the primary xylem, the diarch nature of the root becomes distinct. Secondary xylem far exceeds secondary phloem in volume.
S.album does not have a deep tap root system, and its lateral roots runs almost parallel to the gound and young rootlets produce haustoria which establish connections with neighboring host roots to absorb certain mineral salts; however not all haustoria’s are functional. Roots contain the highest concentration of scented oil compared to any part of the tree. It has been observed that the lateral roots have traveled to a distance of more than 10 meters.
The root wood is yellowish brown or dark-reddish-brown, hard and scented. The structure of well-developed root is essentially similar to that of stem.
Anatomically, both stemwood and rootwood in sandalwood look alike, except that in root wood the vessels appear to be thinner and more frequent.
Flower
The flowers are purplish-brown, minute, odourless, tetramerous, actinomorphic, bisexual, perigynous and regular; they are borne in auxiliary or terminal cymose panicles. The plants are also charecterised by bearing, tri, penta, and rarely hexamerous flowers in the same tree.
The bud is whitish green. In the bud perianth lobes are jointed at the tip and they become reflexed when the flower opens. The perianth persists even when the fruits have attained a large size. The floral organs develop in acropetal succession. The first to appear are the four perianth lobes followed by epigynous staments, carpels and placental column. Flowers are tera to pentamerous; rarely hexamerous and hermaphrodite. The ovary is semi-inferior and unilocular with three ovules lodged in three depression base. According to Paliwal (1956) the depressions at the base of the ovary are formed in later stages of development of flower, when the embryo sac comes out of the ovary of the ovule and crushes the cells at the base of the ovary to form small depressions in which the tip of the ovules and the embroyo sac rest.
The placental column is straight, generally bearing three ovules in hexamerous flowers. However, four ovules are more frequent. The long style is traversed by a narrow canal and terminates in 3 or 4 lobed stigma (Bhatnagar 1965).
Anther
Anther is dorsifixed having four lobes of which the outer two are bigger than the inner two.
The tree begins to flower as early as 2 to 3 years and varying flowering and fruiting seasons are noted. Trees can be classified into three distinct groups depending on the flowering calendar (i) trees flowering twice a year (once during March – May and for the second time during September – December), (ii) trees flowering once a year (September – December) and (iii) trees that do not flower even after 15 years of age (Ananthapadmanabha et al 1991).
The two flushes of flower production may overlap each other so that the same tree may show all the stages of development from flower initiation to mature fruits at one time.
The duration required from the bud initiation stage to the opening of the flower is 30 to 35 days and the duration required from the initial stage to ripening of the fruit is 85 to 95 days. Bagging and emasculation experiments showed that sandalwood is often a cross-pollinated species. Some interesting observation has been made on the flower and inflorescence development by Tony Page and Harington (2010) that flower (i) have longer life of 7 to 9 days, (ii) change in colour from white to red rapidly after opening, (iii) have a smaller and les prominent stigma that do not extend beyond the height of stamens, (iv) have less trichomes at the base of the another filament, particularly within the floral tube and (v) have tepals that open but do not close.
Fruit and Seed
Young fruits are initially green and as they mature the outer colour changes to reddish brown, then purple to black. Mature fruits have a dark purple-black pericarp, and a fleshy dark, juicy mesocarp surrounding the nut. These fruits are attractive to birds and monkeys, which assist in the propagation of species. Excreted fruits are fre from flesh and may germinate sooner than the uneaten fruits.
Seeds are obtained by removing the fleshy portion of the fruit. They are naked and lacking testa. The endosperm contains 50 to 60 percent of drying oil, protein and mineral matter. The stony endocarp is widely referred to as the seed coat although it is a false seed coat.
The dried seeds are stored in gunny bags or in polythene bags and are viable for 12 months. However, the viability can be extended beyond 24 months by storing under carbon-di-oxide and nitrogen and treatment with iodine vapour (Nagaveni and Anantha-padmanabha, 1989).
The protein content of non-viable seeds was found to be significantly lower when compared to viable seeds. This depletion of food reserve also indicates a reduction in the seed viability and germination upon prolonged storage (Anantha-padmanabha et al 1989b) (Table 1).
Table 1 : Fatty acid content and the oil characteristics of viable and non – viable seeds
| Viable seeds | Non-viable seeds | |
| % Fatty oil | 60.0 | 63.5 |
| % Unsaponifiable matter | 7.8 | 12.3 |
| Iodine value | 147.0 | 161.0 |
| % Protein in deoiled seed meal | 60.0 | 41.0 |
(Anantha-padmanabha et al., 1989)
Germination
Germination is epigynous, the radical emerging out by breaking through the false seed coat after 25-30 days. The hypocotyls elongates by very pronounced arching, the loop appearing above ground while cotyledons remain underground. The lower portion of the hypocotyls becomes swollen and fleshy. The nutrients from the endosperm passes on to the lower protion of hypocotyl, which becomes swollen and fleshy, this swollen portion is also referred to as ‘carrot’ of the seedling. Later, after transference of nutrients, the hypocotyls becomes erect throwing the cotyledons above the ground Cotyledons break off as the young foliage leaves develop above them.
Seed dormancy
Fresh seeds will show dormancy for around 2 month’s period, however seeds obtained in Australia and Sri Lanka do not show dormancy. It is likely the enforced dormancy of seeds is due to the presence of hard seed coat or due to presence of chemical substances in the seed coat which makes it impervious to water and gases. Treatment with a dilute solution of sodium hydroxide or dilute hydrochloric acid or gibberellic acide can remove the dormancy of seeds (Anantha-padmanabha, et al.,1988). Soaking seeds with gibberellic acid (0.05%) (Nagaveni et al 1998) overnight was found to be effective in bringing down the length of the dormancy period and inducing quicker and more uniform germination in about 25 to 30 days.
Early and quick germination in a short time of 15 days by breaking the false seed coat, indicates the presence of inhibitory principles in the seed coat (Srimathi and Rao, 1969).
Seed polymorphism
Sandal seeds, which exhibit polymorphic form, maintain its indentity in respect of germination, occurrence and other characters (Nagaveni and Anantha-padmanabha, 1986). The seeds can be grouped into three categories, small (diameter 7mm), medium (diameter 7-8mm) and big (diameter 8mm). Small seeds of less than 7 mm in diameter size exhibited higher percentages of germination compared to those of medium and big sized seeds. The seeds are also having small characters like three ridges and four ridges at one end.
Table 2: Seed polymorphism and germination
| Seed category | Seed weight (g) | Seed size (mm.dia) | % of occurrence | Viability in months | Germination % up to 60 days | Survival % of seedlings |
| Small | up to 0.1 | 7 | 10-13 | 7-9 | 55-69 | 55-60 |
| Medium | 0.1-0.2 | 7-8 | 82-87 | 10-12 | 45-47 | 70-75 |
| Big | 0.2 | 8 | 3-5 | 12-14 | 32-35 | 90-95 |
| Seeds with 3 ridges | 0.1-0.2 | up to 8 | 82-85 | 10-12 | 45-47 | 70-75 |
| Seeds with 4 ridges | 0.10-0.2 | up to 8 | 15-18 | 10-12 | 45-47 | 68-72 |
(Nagaveni and Ananthapadmanabha1986)
The seeds collected at Sri Lanka seem to give higher percentage of germination than other areas, achieving over 75 percent. The variation of germination rates may be due to local factors. Seeds collected from trees of four years of age can also be used for propagation.
Viability germination
Viability and germination capacity are two independent components are not all viable seeds germinates. The viability and germination decreases with the age of seeds, optimum germination can be achieved from seeds stored for 6 to 8 months. Viability decreases after 12 months considerably (Fig.14) and exceeds beyond 24 months by storage under carbon-di-oxide, nitrogen and also treating them with iodine vapor (Nagaveni and Anantha-padmanabha 1989) (Fig.15).
SOILS
A precise knowledge of soil is of great value in managing forests and plantation for increasing productivity, as it helps in correlating site conditions with regeneration, growth, distribution and successful establishment of commercial plantation; however S. album has no barrier for the type of soil texture or structure. It adapts well to different climatic and soil conditions. It is commonly said, “While other tree species requires soil with good nutrients for its growth and establishment, Sandalwood trees grows well even though soil is not fertile”.
Occurrence in different soil type
Red ferruginous loam is the most common soil on which sandal tree occurs, the underlying rock often is metamorphic and is chiefly geneiss. In India S.album occur in different type of soils; like laterite, sandy loam, geniss quartz, black clayey soils.
The soils should be moderately deep with good drainage with good physical properties, mostly acidic to neutral, with soil pH 6.5 to 8.5
In Indonesia, trees grows well in well-drained soil and adapt to rocky or stoney soils with low fertility. In Australia, ORIA (Ord River Irrigation Area) soil is described as black cotton soil texture of Kanunurra clay derived from recent river alluvia with an alkaline pH of 7.8 These soils are dark brown self-mulching plastic clays. They have poor drainage when wet. In Sri Lanka, it occurs in different type of soil ranging from lateritic to sandy loam and clay.
Mei Qi-wen et al (2011) during their studies on the influence of rhizosphere pH value of the host on growth of Indian sandalwood found, that the root length and shoot height are significantly higher at pH 5.5 The tree grows best in the weak acidic condition. However, they also feel, there is no evidence to prove for the optimum rizospheric pH for sandalwood tree, but there could be some veiled association between the host parasitic relationships. Their study was based on change of sub-localisation of acid phosphate (ACP) during the haustorial development.
Influence of soil on growth and heartwood formation
In a study carried out by Jain et al., (1988) on soil properties and their relationship to the growth of sandal in three areas, it was observed that lime status, water holding capacity, pore space, volume expansion on wetting, exchangeable calcium and magnesium and available potash, exert positive influence on the increment in girth and height. It was observed that specimens obtained from trees on relatively poor rocky gravely soils had higher oil content than those of specimens from fertile soils. It is believed that the best growth of sandal can be seen when it is growing in fertile soil and in association with xerophytic conditions and suitable host.
Soil in relation to incidence of spike disease of sandal
The spike disease of sandal has been studied from various angles and due attention has also been given to understand the role of soil on the incidence of spike disease.
Comparison of data of the soils from healthy and spiked areas showed that under spiked threes they were calcareous and had lower quantities of available nutrients, especially phosphorus, whereas those having healthy sandal plants were all non-calcareous and had higher amount of available nutrients. Hence, it was viewed that calcareous nature and low amount of available nutrients in the soil may serve as predisposing factors for the onset of the disease (Khan and Yadav, 1962).
The nature and properties of soil as such may not directly influence the incidence of spike disease. However, in combination with other ecological and edaphic factors, it could serve as a predisposing factor for the onset of the disease.
PHYSIOLOGY
Scott (1871) reported the parasitic nature of sandalwood plants; for many years, importance of this was not realized for good growth of trees. Barber, in 1902 examined the roots of sandalwood trees in connection with the study of spike disease and made detailed investigations on the formation and structure of haustoria’s and their mode of attachment to the root of host plant.
Haustoria on roots of sandalwood seedlings arise from external layers of rootlets, unlike lateral rootlets, which are formed deep in its tissues. If a rootlet of neighboring plant is met, sandalwood seedling grows rapidly attaching itself closely to the tootlet and develops into a mass of white tissue. It is first club-shaped but later enfolding the surface of the root attacked, it assumes the shape of a flattened bell. Usual dimensions of a fully developed haustorium are, height 3-10 mm, longer diameter 2-12 mm, shorter diameter 2-8 mm. Formation of haustoria is more or les confined to the younger roots (Fig.16).
Rama Rao (1911) from his experiments concluded that sandalwood seedlings were incapable of growing beyond one year without haustoria. He also endorsed the opinion of Barber on the selective habhit of sandalwood trees in relation to hosts.
The host parasitic combination differs from region to region the natural population.
It shows decided preference and grows best in association of certain species. The order of preference seems to be Casuarina equisitfolia, Pongamia pinnata, Albizia lebbeak, Cassia siamia, Acacia spp, Dalbergia latifolia, D.sisso etc. (Anantha-padmanabha et al. 1984).
In Australian plantations, the performance of sandalwood with Cassia siamia, Pongamia pinnata, Cathomium umbellatum and Acacia trachycarpa is very good. Swietenia mahogany tried as long term host initially did not support the growth of sandalwood.
Mixed plantation of S.album with Dalbergia odorifera in China proved to be the best potential long term host, where as other hosts like Acacia confuse, Bischofia polycarpa and Dracontomelon duperreranum did not support good growth of sandalwood.
Sandalwood grows well with Gliricidia spp. in Sri Lanka; it is preferred because the growers can cut and sell the branches periodically. It is a very fast growing under tree.
It has been noticed that the roots of sandalwood tree had traveled a length of nearly 40 m and attacked the roots of a large Pterocarpus marsupium tree (Venkata Rao, 1938). Generally parasitic plants are smaller in size than their hosts with a single exception of sandalwood tree.
Tracer technique studies have shown that calcium could be absorbed by the roots of sandalwood seedlings, while phosphate, organic substances, amino acids, sugars and mineral phosphates were drawn from the host plant (Kunda S. Deval et al., 1974a, b).
Iyengar (1950) while studying the parasitic nature of sandalwood trees expressed that the parasite may draw only its mineral nutrients including water from host, but with green foliage it can synthesizes its own carbohohydrates like autophytes. The possibility of absorbing some organic material from host is not excluded, parasite.
Xinhua Zhang et. al (2012) has made an interesting observation on the physiology of haustorial formation. They are of the opinion that a high auxin-to-cytokinin ratio contributed to haustorial development of S.album. Numerous amount of starch in parenchyma cells around the meristamatic region above the haustorial gland and the endophyte tissue of the post-attachement haustoria were reported in Santalaceae members. Many Lysosomes were present and large-scale digestion of host cells occurred at the interface between the host and the parasite. The haustorial penetration in to the host stele was suggested to be a function of mechanical force and enzymatic activity. Analysis of the endogenous hormone levels and the structural characters in haustoria indicated that haustoria were able to synthesise phytohormones, which appeared to be necessary for cell division and differentiation during haustorial were able to synthesise phytohormones, which appeared to be necessary for cell division and differentiation during haustorial development. The authors are of the opinion that endogenous hormones are involved in the haustorial development and also transport of water and nutrients during host-parasite association.
Even when the science had not advanced much Barber (1907) was able to make a number of observations on the structure of the haustoria beginning with the formation of cushion like bodies from sandalwood roots to complete penetration inside the host roots and establishing intimate attachment between them. The haustorial connection proceeded in two stages, in the first stage, rupture and then penetration of the host root till it reached the woody portion. In the next stage, a channel communication between haustoria and vessels of the sandalwood roots is formed (Fib.17). The presence of auxin in the haustorium was reported by Srimathi and Sreenivasya (1962). Xinhua Zhang (2012) findings are an additional proof for the formation of haustoria.