MECHANICAL METHODS TO STIMULATE ALOES WOOD FORMATION IN AQUILARIA CRASSNA PIERRE EX H.LEC. (KRITSANA) TREES

Various mechanical injury methods were tested to induce formation of aloes wood in 4-year-old Aquilaria crassna Pierre ex H.Lec. (kritsana) trees grown at Phurua Highland Agricultural Experiment Station, Phurua, Loei (950 m asl, 17°17’N 101°24’E) during February 2001 to October 2002. A sequential change in the wood coloration was observed around injury sites. One month after wounding a pale discoloration occurred, followed by a darker yellow-brown discoloration after 3 months, becoming dark brown within 8-10 months and changing to black within 20 months with accompanied on burning scent. Wood block samples collected from live tree at 10, 15 and 20 months after wounding were compared among the different mechanical treatments. The results indicated that holes made with screws, wounds inflicted with chisels and bark removal with hatchets on the trunk gave dark yellowbrown to dark discoloration near injury (5-10 mm from the cut end), while nails hammered into the trunk gave dark brown to black occurring by the interaction between ferric oxide and fibers, where as hammers beated on the trunk gave only little discoloration. The larger the objects used to wound the trunk of kritsana trees, the wider the width of the discoloration ring. The rate of the formation of the discoloration ring around the wound in the rainy season (16-20 months after wounding) was 3 times higher than in the dry season (11-15 months after wounding), influenced by seasonal factors. Most treatments gave no specific aromatic kritsana scent by burning the wood samples, except only 4 treatments gave pale scent which were the holes made with screws (1.27 cm and 1.11 cm in diameter) and wounds inflicted with narrow (1 cm) and wide (2.54 cm) chisels. Moreover, the wood samples gave very low percentage yields of essential oil using a hydro-distillation method. In conclusion, mechanical injury can be used for the formation of aloes wood in kritsana trees, and the most suitable method was the holes made with screws (1.27 cm in diameter) which gave the widest discoloration ring and pale specific aromatic kritsana scent by burning. INTRODUCTION Aquilaria (Thymelaeceae) is indigenous in India, Bangladesh, China, and Burma and extends through Southeast Asia to the Philippines (Ding Hou, 1960, 1964). Only 3 out of 15 species of this genus are known in Thailand: Aquilaria crassna Pierre ex H. Lec. , A. malacensis Roxb. (Syn. A. agallocha Roxb.) and A. subintegra Ding Hou (Siripatanadilok, 1982). Few trees are know for producing the aromatic portion of wood known as agarwood or agar (Hindi), gaharu (Indonesian), aloes wood (English) (Chung and Purwaningsih, 1999), and kritsana (Thai). Aloes wood or kritsana contains patches of oleoresin deposits which have been traded in Thailand for 700 years (Anuwatvanarak, 1942). Aloes wood has been prized for thousands of years in Egypt, Arabia and throughout the East for use as incense, perfumes, drugs, stimulants, cordial tonics, carminative and is an ingredient in several compound preparations (Atal and Kapur, 1982). Aloes wood is found in the market in the form of chips and splinters and also as blocks. Aloes wood has a slightly bitter aromatic taste and a peculiar scent, comparable to that of sandalwood or ambergris. It burns with a bright flame or smolders, giving off a pleasant scent of aromatic oils. True aloes wood is hard, heavy, brown and rich in resin. Proc. WOCMAP III, Vol 2: Conservation Cultivation & Sustainable Use of MAPs Eds.: A. Jatisatienr, T. Paratasilpin, S. Elliott, V. Anusarnsunthorn, D. Wedge, L.E. Craker and Z.E. Gardner Acta Hort. 676, ISHS 2005 162 Black and heavy aloes wood commands the highest price in the market. A soft and yellow white variety is of inferior quality. It is used to distil volatile oils in a cottage industry called agar attar (Rao and Bhatia, 1959). Few analyses of the volatile components of aloes wood have been made. Analyses made in Switzerland revealed agarofuranoids and sesquiterpenoids of the eudesmane, eremophilane, valencane and vetispirane type as the main components (Naf et al., 1995). An analysis from Japan of essential oil obtained from aloes wood identified as originating from A. malaccensis, using diethyl ether extraction of the highest quality aloes wood, revealed that oxygenated sesquiterpenes and chromone derivatives are the main components of the essential oil (Ishihara et al., 1993a). The main components identified in the smoke obtained by heating the wood to about 200°C belonged to the same group of components (Ishihara et al., 1993b). Previously scientists believed that aloes wood was a pathological product, formed as the result of infection of the wood by Fungi Imperfect (Jalaluddin, 1977), but recently Rahman and Basak (1980), Rahman and Khisa (1984) and Gibson (1977) reported that there was no primary role of any specific fungus in the formation of aloes wood. Chalermpongse et al. (1990) reported that kritsana or aloes wood (oleoresin deposit) formation did not correlate with infection by specific fungi, but was formed by the tree in response to injury. Because of their high value Aquilaria, trees were often cut indiscriminately. The trunks of felled trees were cut into pieces and collectors then cut through the entire tree to locate the aloes wood (Chung and Purwaningsih, 1999). Therefore, the Royal Forestry Department of Thailand began to allow farmers to grow kritsana trees in 1992 to prevent the indiscriminant harvesting of Aquilaria for aloes wood. At present, many farmers in all parts of Thailand grow kritsana trees, but there are no reliable techniques available to guarantee formation of aloes wood. Therefore, the objectives of this research were to determine suitable methods of mechanical injury to induce formation of aloes wood. MATERIALS AND METHODS Four-year-old Aquilaria crassna Pierre ex H. Lec (kritsana) trees were grown at Phurua Highland Agricultural Experiment Station, Phurua, Loei. (950 m asl, 17°17’N, 101°24’E). The trees had an average of 4.66 ± 0.67 m canopy height, 1.69 ± 0.44 m canopy width and 45.24 ± 8.83 cm trunk girth (measured at 10 cm above the ground). Four simple mechanical injury techniques (gouge with chisels, hole with screws, bark with hatchet and puncture with nails) were applied to induce formation. The experimental design was a randomized complete block design (RCBD) with 4 replications per treatment (13 treatments + 1 control). Each replication was comprised of 3 plants. The treatments applied were: treatment 1-2 wounds inflicted with wide (2.54 cm) and narrow (1 cm) chisels; treatment 3-6 holes made with screws of 4 sizes (0.40, 0.55, 1.11 and 1.27 cm in diameter); treatment 7 was barked removal with hatchets; treatment 8-12 were nails of 5 sizes (2.54, 5.08, 7.62, 10.16 and 12.70 cm long) hammered into the trunk; treatment 13 was hammers beated on the trunk; and treatment 14 was control (no mechanical treatment). All treatments were applied in late February, 2001 on the trunk of kritsana trees in the range of 50 to 150 cm above the ground. Visual observation of the wound were conducted every 15 days during March, 2001 to October, 2002; and wood sections were obtained from trees at 10, 15, and 20 months after wounding. The statistical program; SPSS for Windows version 8.0 was used for data analysis. All kritsana wood pieces (kept at 20 months after wounding) from 14 treatments were distilled by a hydro-distillation Cleavenger apparatus at Department of Pharmacognosy, Faculty of Pharmaceutical Sciences, Chulalongkorn University. Compared the quantity of the essential oil among all treatments. A citation panel of 20 people, (1) used the smell to detect the scent obtained by burning the kritsana wood pieces from 14 treatments compared with the commercial kritsana (Soi Nana, Bangkok); (2) were asked to identify the scent detected, based on the scent by burning the commercial kritsana wood pieces; and (3) scored the data to the ordinary scale (Likert scale) and analyzed by the statistical program: SPSS for windows version 8.0.