Studies On Artificially Induced Heartwood Formation Of Dalbergia Odorifera

Dalbergia odorifera T.Chen, commonly known as Hainan rosewood, which is asemi-deciduous arbor tree species belonging to Papilionaceae, Dalbergia L.. The heartwood ofDalbergia odorifera and volatile oil distilled from the heartwood have very high economicvalue. The tree species grows slowly under natural conditions, heartwood became useful after30~40years old, and tree value is increased with the tree age. Now a large area of Dalbergiaodorifera were planted in southern China region, but the study on the plantation growth,heartwood formation condition and volatile oil is very limited.In this paper, the growth and heartwood formation condition were investigated of6~8year-old for Dalbergia odorifera from Hainan, Guangdong, Guangxi and Fujian, the initialforest age of heartwood formation was determined and plantations cultivated suitability waspreliminary assessmented. In addition, a series of experiments including drought stress, growthregulator injection and fungus liquid instillation were conducted to accelerate heartwoodformation, the possible mechanism of heartwood formation was speculated through the growth,physiological characters and analysis of induced heartwood. Finally the effective artificialinduction method was screened. The main conclusions of the research were as follows:(1) The heartwood can form naturally in large-scale Dalbergia odorifera plantations.Heartwood formation was closely related to the DBH,8~10cm in DBH could be a criticalcreteria for heartwood formation. At the stage, the proportion of heartwood was low andproportion of heartwood diameter at30cm height was about15%and average volatile oilcontent was3.60%, compared with the standard sample, the quality of the heartwood volatileoil was not high in most of the areas.(2) The tree height, DBH, ground diameter and branch height increased respectively1.08m,1.05cm and1.21cm under900mm treatment after one year by water supply. Increment ofgrowth indicators under900mm treatment was significantly higher than other treatments which indicated that900mm treatment would be more favorable for6year-old Dalbergiaodorifera tree growth. The leaf SOD and POD activity increased with the drought stressincreased, the maximum value was329U·g-1FW and1803U·g-1FW under0mm treatment.The protective enzyme activity of Dalbergia odorifera leaves increased in response to externalstress indicated that6year-old Dalbergia odorifera had drought-resistant capacity. Allmoisture and drought treatments can induce heartwood formation. Heartwood area under2700mm treatment was the largest while0mm treatment was the smallest, but the heartwood colorunder0mm treatment was the deepest. Treatment with0mm had the highest volatile oil of5.04%which was significantly higher than other treatments. Compared with the standardsample, main components of the volatile oil under0mm treatment were consistent. It can bespeculated that water condition would be favorable for high-quality heartwood formation ofDalbergia odorifera.(3) The plant growth regulators had no significant effect on the growth of tree height,DBH, ground diameter and height under branch for Dalbergia odorifera. The maximum valuesof SOD, POD and CAT activity under2%of ABA treatment were significantly higher than theother treatments, the values were as follows:258U·g-1FW,1649U·g-1FW and271U·g-1FW,indicating that2%of ABA treatment had severe physiological stress effects on Dalbergiaodorifera tree species. All the plant growth regulators reatments could induce heartwoodformation. Heartwood area under ETH and6-BA treatment was larger than the other treatmentswhile paraquat treatment was the smallest. In addition to paraquat treatment, heartwoodvolatile oil content under other treatments were significantly higher than distilled watertreatment(CK). Compared with the standard sample, it can be speculated that ETH and6-BAtreatment can induce high-quality heartwood formation.(4)6-BA treatments had no significant effect on the growth of tree height, DBH andground diameter for Dalbergia odorifera. All the6-BA reatments could induce heartwoodformation，but B-4treatment could induce the more heartwood than other treatments. Heartwood volatile oil content under B-4treatment was significantly higher than othertreatments, can induce the high-quality heartwood formation.(5) The fungus liquid instillation had no significant effect on the growth of tree height,DBH, ground diameter and height under branch for Dalbergia odorifera. The variation trend ofSOD, POD and CAT activity was disorder while the vaule under Pestalotiopsis palmarumtreatment was significantly higher than the other treatments, the maximum values were asfollows:338U·g-1FW,1967U·g-1FW and547U·g-1FW, indicating that Pestalotiopsispalmarum treatment had severe physiological stress effects on Dalbergia odorifera tree species.All the fungus liquid instillation treatments could induce heartwood formation. Heartwood areaunder fungus liquid instillation treatments was larger than distilled water treatment(CK).Heartwood area with Pestalotiopsis palmarum treatment was the largest while the heartwooddistribution located up and down the25cm from the drill holes. Treatment with Pestalotiopsispalmarum had the highest volatile oil of5.47%which was significantly higher than othertreatments. Compared with standard sample, The main compounds of heartwood volatile oilinduced by fungus liquid treatments was similar while the relative content was differences.Heartwood induced by Pestalotiopsis palmarum was consistent to standard sample indicatedthat liquid of Pestalotiopsis palmarum injection could induce high-quality heartwoodformation.(6) PAL was the committed step enzyme in synthesis of flavonoid extract and showedhigher activity at the peak period of plant heartwood formation. The leaf PAL activity ofDalbergia odorifera in November was higher than July and September in the experiment, so itcould be speculated that November was probably the good period of Dalbergia odoriferaspecies heartwood formation.(7) The heartwood formation of Dalbergia odorifera was mainly due to external stimuliincluding drought stress, plant growth regulators and fungus liquid. The external stress canalter the balance of the tree internal metabolic and the variation of enzyme activity, or directlyas heartwood inducing substance to accelerate the sapwood converted to heartwood.