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In this article we will discuss about:- 1. Characters of Santalaceae 2. Distribution of Santalaceae 3. Economic Importance 4. Affinities.
Characters of Santalaceae:
Plants mostly semi-parasites, flowers tetra or pentamerous; 3-5 carpellate, ovary unilocular, single basal ovule with integument reduced to one or absent and the seed without a seed-coat.
A. Vegetative characters:
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Habit:
Plants semiparastic herbs, shrubs or small trees, mostly semiparasites on branches of trees or on roots e.g., Santalum album L. (Swet chandan) is a root parasite, Thesium humifustum DC is a herbaceous root parasite. The Seedlings get themselves attached to the host by suckers.
Root:
Tap-root, gives suckers or houstoria which penetrate into root or rhizome of host plants.
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Stem:
Erect, branched, herbaceous or woody, solid, cylindrical.
Leaf:
Simple, entire, opposite, sometimes alternate, leathery, exstipulate, petiolate, foliaceous or reduced to scales.
B. Floral characters:
Inflorescence:
Various types—racame, spike, head, dichasial sometimes flowers are axillary solitary.
Flower:
All transitions from bisexual to unisexual, staminate or pistillate; dioecious plants with unisexual flowers (Osyris pyrularia, Comandra ulmbellata).
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Perianth:
3 tepals (Osyris), pentamerous perianth, either sepaloid or petaloid, valvate aestivation.
Androecium:
Stamens as many as perianth, opposite, epiphyllous, filaments short, anthers bithecous, basifixed, dehiscing vertically; a tuft of hairs present behind each filament.
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Gynoecium:
Carpels 3-5 (rarely 2) syncarpous, ovary inferior or semi-inferior, unilocular, ovules 1-5 usually 3, differentiate from placenta, basal placentation or only one fertile borne on the apical end of central placenta, and pendulous, ortho-to anatropous, ovule without integument.
Fruit:
Achene or drupe.
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Seed:
Seeds without testa with fleshy endosperm, embryo straight.
Pollination:
Entomophilous due to nectar secreting disc, often present.
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Floral formula:
Haustoria:
The members of the family Santalaceae are parasites. They are attached to the hosts by means of haustoria. The haustoria penetrates the root of the host-which is of other angiospermic family; as far as xylem, as a result the vessel of the host and that of parasite become organically joined, the inter-communicating elements are known as ‘phloeotracheids’ but according to Rao the intercommunicating elements are true vessels, i.e., tracheae not tracheids.
Haustroia may be simple or compound, the compound types occur in species attacking hosts having hard roots difficult for penetration. In both types of haustoria glandular activity is marked on the surface of haustoria, the glands secrete some substances which help the haustoria for penetration.
The structure of a mature haustorium is like an inverted flask. The vessel of the haustorium becomes opposed to those of the host and finally organic concentration between the vessels of the host and parasite is established. The haustoria undergo secondary thickening also.
Distribution of Santalaceae:
Santalaceae comprises of 26 genera and from 250 (Engler & Gilg) to 600 species(Rendle) and distributed throughout temperate and tropical regions.
Economic Importance of Santalaceae:
1. Food:
The fruits of Acanthosyris fulacata and Exocorpos cupressiform is and tubers and Arjona tuberosa are edible.
2. Flavour:
An essential oil, distilled from the heart wood and roots of Santalum album are used in perfumery. The sawdust of heart wood is made into scented cakes and sticks to be burnt as incense. Roots of Santalum album are used in perfumery.
3. Medicinal:
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The sandal wood ground up into a paste is commonly applied to local inflammation, to the temples in fever and to skin diseases to allay heat and pruvitus. The bitter wood is cooling, exhilling, antiseptic, diaphoretic, aphrodiasiae and useful in diseases of heart, thirst, biliouness, burning sensation, bronchitis, vaginal diseases etc.
4. Timber:
Colpoon compressum, Eucarya, Spicata, Santalum freycinetianum and S. yasi yield valuable wood. The heart wood of Santalum album is employed for boxes, combs, fancy articles, cabinet work, picture frames furnitures, etc.
5. Ornamentals:
Species of Buckleya and Pyrularia are cultivated as novelties.
Affinites of Santalaceae:
The Santalaceae is closely allied to Loranthaceae in some characters of perianth, ovary and seeds. The plants of Santalaceae are semi-parasitic or parasitic only in roots and those of Loranthaceae are aerial parasites. There is strong resemblance of Santalaceae in foliage and inflorescence of Myrtaceae (Richardson, 1978).
Exocarpus (Manas, Ram, 1959) (member of Santalaceae) has a naked semi-inferior ovary with single, sessile naked ovule with pollen chamber resembling Gymnosperm, further, the ovule does not show any differentiation form necellus and embryosac.
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This genus is a reduced member of the fami Santalaceae, not a Gymnosperm as treated by certain authors. Lam (1948) commented that the “Exocarpus” … probably represents a transition between the protoangiosperms gymnosperms and Monochlamydeae. Swamy’s work suggested no link between Exocarpus and the gymnosperms.
Ram (1959) showed that the flowers of Exocurpus possess perfect angiospermous features. Maheshwari & Kapil (1963) assigned Exocarpus to the Santalureae rather than to the Salicaceae or Casuarinaceae.
Common plants of the family:
1. Santalum album – Sandal wood (Chandan) -indigenous in S. India.
2. Osyris alba – Dioecious plants with unisexual flowers.
3. Pyrularia – Dioecious shurb or tree-one species in Himalaya.
4. Thesium himalyensis – Root parasite in Kumaon.
Division of the family and chief genera:
According to Pilger Santalaceae has 3 tribes viz.:
Tribe I: Anthoboleae:
Perianth hypogynous; ovary superior, uniloclar with single basal orule sunk at the base of the disc. Fruit on fleshy swollen end of the pedical. Genera. Anthobolus, Exocarpus etc.
Tribe II: Osyrideae:
Perianth more or less epigynous, Receptacle not grown far above the orary or shorter companulate on the ovary and then more or less adnate to the disc. Genera: Osyris, Leptomeria etc.
Tribe III: Thesieae:
Perianth epigynous, Receptaele over the ovary grown into a tubular structure, not adnate inwardly to the disc. Ovary inferior. Genera: Thesium, Ariona etc.
