Online Manual for the Forest Tree Seeds of Kerala

A Kerala Forest Department Funded Project


Dr. K Sudhakara
Professor & Head of the Department
Dept. of Silviculture & Agroforestry
College of Forestry, Kerala Agricultural University, Thrissur 680 656
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Scientific Name  Acacia mearnsii de Wilde
Vernacular name  Chavukku, Seekai (Tamil) (Chacko et al., 2002).
Common name  Black wattle (Chacko et al., 2002).
Synonyms  Acacia decurrens (Wendl.) Willd. var. mollis Lindl., Acacia mollissima Willd. (Chacko et al., 2002; Duke, 1983).
Family  Leguminosae
Subfamily  Mimosoideae
Origin  Australia (Ram Parkash and Drake Hocking,1986).
Distribution  Native to Southeast Australia (Victoria to New South Wales and southern Queensland) and Tasmania. Introduced and cultivated widely for afforestations. In India it is grown in Nilgiri and Palni hills (Duke,1981a; Ram Parkash and Drake Hocking,1986).
Description  Medium sized evergreen tree upto 27m height and 47 cm diameter; crown conical or rounded. Foliage is dark green. All parts except flowers are usually pubescent or puberulous; stems without spines or prickles (Chacko et al., 2002; Ram Parkash and Drake Hocking, 1986; Duke, 1981).
Flowering season  January to February.
Fruiting season  November (Khullar et al., 1991).
Flowers  Flowers in pale yellowish globose heads, fragrant, borne in panicles or racemes, on peduncles 2-6 mm long distributed in terminal or axillary position (CSIR, 1948; Duke, 1981a).
Fruits  Grey-puberulous, or sometimes glabrous, almost moniliform, hard, dehiscing, usually 3-10 cm long, 0.5-0.8 cm wide, with 3-14 joints (Duke, 1981).
Fruit type  Pod.
Seeds  Smooth black, elliptic or compressed ovoid, seeds, 3-5 mm long, 2-3.5 mm wide; caruncle conspicuous; areole 3.5 mm long, 2 mm wide (Duke, 1981a).
Seed length  0.42 cm (Chacko et al., 2002).
Seed width  0.29 cm (Chacko et al., 2002).
Seed thickness  0.18 cm (Chacko et al., 2002).
Seed weight  45,000 seeds/kg (Kindt et al., 1997; Chacko et al., 2002); 85,000 seeds/kg (Carlowitz, 1991; Chacko et al., 2002).
Seed dispersal 
Seed Collection  Collect pods from the tree by lopping off the branches in the month of November (Chacko et al., 2002; Srivastava et al., 2006).
Transportation of seeds  Pods collected in cotton / polythene / gunny bags are packed and transported (Chacko et al., 2002).
Seed processing  Sun dry the pods until they dehisce and extract the unreleased seeds by beating with a stick (Chacko et al., 2002).
Seed storage  Orthodox (CABI, 1998; Kindt et al., 1997; Chacko et al., 2002). Seeds are dried before storage and stored in sealed tins or polythene bags for more than a year (Chacko et al., 2002).
Viability period  Under ambient room temperatures, seeds are viable for one year (Chacko et al., 2002). 1-2 years (Srivastava et al., 2006).
Seed emptiness  Low (Chacko et al., 2002).
Seed pre treatment  Soak the seeds in cold water for 48 hrs or in hot water for about 3 min followed by cold water soaking for 24 hrs (Kindt et al., 1997; Chacko et al., 2002). Autoclaving the seeds for 20 and 25 min are enough to break the dormancy (giving 90% germination) and simultaneously to disinfest the seeds. Periods less than 20 min are not efficient in disinfestation although they promote high rates of germination (Martins Corder et al., 1999). Seeds exposed to constant dark conditions show better germination percentage (Kulkarni et al., 2007). Soaking seeds in hot water for 12-24 hrs or stirring in concentrated H2SO4 for 1 hr. Steeping of seeds in hot water for 5 min is sufficient to break dormancy (Gupta and Thapliyal, 1974).
Germination type  Epigeal (Chacko et al.,2002).
Germination percentage  50 to 83 (Carlowitz, 1991; Chacko et al., 2002). Mechanical scarification, hot water treatments, scarification with sandpaper, and photoperiod treatment for 12 hrs give 98%, 82-86%, 58.75-80% and 72.36% germination respectively (Martins Corder et al., 19
Germination period  30 days (Khullar et al., 1991);2 to 10 days (Chacko et al., 2002).
Nursery technique  The pre-treated seeds are sown in plastic trays containing vermiculite and watered regularly. When the seedlings are about 4 to 5 cm high, they are transplanted to the polythene bags of size 20 x 10 cm filled with soil or compost based potting mixture and maintained under shade (Chacko et al., 2002). Combined vermicompost+gypsum treatment increase growth, biomass and growth index of seedlings, when compared to individual treatment of fertilizer (Rajan and Mariappan, 2003). Vermicomposts should be applied at 56-112 cm3 to produce quality seedlings (Caldeira et al., 2000). Phosphorus utilization efficiency decrease with increasing P fertilizer doses and inoculations with G. deserticola and Rhizobium sp. (Udaiyan et al., 1997).
Method of propagation  By seeds and root suckers (CSIR, 1948).
Vegetative propagation  Micropropagation of Acacia mearnsii: Nodal explants are taken from 30 day old micropropagated plantlets and pretreated 3 and 9 month old seedlings. It is then induced to form multiple shoots by culturing on MS medium supplemented with 2.0 mg benzyladenine/litre. Rooting is achieved on MS medium supplemented with 1.0 mg IBA/litre. Plantlets are acclimatized in transparent plastic containers under greenhouse conditions with a 90% success rate (Beck et al., 1998). Vegetative propagation is possible using 10-15 cm cuttings with leaves. Mist spray, constant heat of 28oC, and auxin mixtures of IBA and NAA appear essential to good rooting. Bud-grafting can be highly successful (Garbutt, 1971). Propagation by cuttings is almost impossible without mist. Air layering is more promising (Duke, 1983). Rooting of cuttings from the lower branches of trees kept in Hoagland solution containing added ZnSO4, H3BO3, caffeic acid, Vitamin B, amino acids and sucrose; application of an auxin mixture by the quick-dip method (Zeijlemaker, 1976).
Pests  The cracks and crevices of the bark are home for many insects, the very rare butterfly Tasmanian hair streak butterfly lays eggs in these cracks. Melanterius maculatus, seed eating weevil cause reduction in seed number. Larvae feed on developing seeds and adults feed on the green pods and pinnules (Milton et al., 2003). Kotochalia [Acanthopsyche] junodi (Wattle bag worm) in plantations (Hepburn, 1973).
Diseases  Moderate (51%). Twelve species of fungi are recorded. Cylindrocladium parvum, Gonatobotryum sp., Pestalotia sp., are important ones (Mohanan and Anil Chandran, 2001; Chacko et al., 2002). Susceptible to root collar girdling (Neville, 1987).
Medicinal properties  It is used as a styptic and astringent. Alkaloid content is less than 0-02% styptics or astringents (Duke, 1981).
Uses  The bark is one of the richest vegetable tanning material known to the tanning industry. The timber is a valuable by-product and the tree yields a gum (CSIR, 1948). Used as a source of tannin, fuelwood, charcoal, poles, props, green manure and windbreaks. The wood has a calorific value (dry) of 4600 kcal/kg and ash content of about 1.5%. It is dense, with specific gravity about 0.75, and yields a high-quality charcoal (NAS, 1980). Wattle bark contains 30-45% (dry basis) high-quality tannins and is the most widely used tannin material in the world which are particularly effective on hard leathers for shoes and saddles. They give better colour to leather than other tannins, do not precipitate in acid solution, and penetrate hides faster (Purseglove, 1968; NAS,1980). Plantations are grown for kraft pulping and papermaking (Muneri, 1997).
Wood properties  The sapwood is white, which gradually emerges into light red heartwood. It is hard and heavy. The wood is excellent as fuel wood and charcoal. The wood has a calorific value of 3,5000-4,000 k cal/kg. It serves as a fibrous raw material of the pulp, paper and the board industry (Purkayastha, 1996).
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