| Sandal (Santalum album) or east Indian sandalwood, one of the most important economictree species promoted for large area planting in southern China in recent years, is highlyvaluable for its aromatic heartwood and the essential oil distilled from its fragrant heartwood.Heartwood formation is a very complicated physio-biochemical process in sandal, and it willtake10~13years to form heartwood generally in India. Although sandal has introduced intoChina more than40years, and early growth is pretty well, information on heartwood formation,oil content, oil composition, oil distribution, ingredient distribution as well as oil quality is veryscare, and need a further study, because the economic value of sandal will depend largely onthe volume of heartwood, essential oil content, oil composition and oil quality.This dissertation strives to study the heartwood presence, essential oil content, essentialoil composition as well as ingredient distribution of sandal based on a21-year old maturesandal plantation in Jianfengling, Hainan island. Meanwhile, the growth, heartwood presence,oil content as well as oil composition of6-year old young sandal trees which planted inlarge-scale in Guangdong province were also studied through a sample plot survey method. Inaddition, a series of experiments including gas filling, chemical injection as well as fungiinoculation were conducted in order to accelerate heartwood formation in young sandals.Major conclusions are summarized as follows:(1)21-year old sandal plantation in Jianfengling, Hainan island have formed heartwoodnaturally with an average heartwood proportion of38.01%, an average oil content of5.52%,both content of α-santalol and β-santalol extracted from heartwood have achieved the currentISO standard for sandal oil.(2)No significant differences of oil content (p=0.583) was found among different parts ofheartwood (part referred to east, south, west, north and center or pith), but their was significantdifferences (p<<0.001) between different locations (location referred to sapwood, outerheartwood, central heartwood and center or pith). Oil extracted from sapwood was lower than that extracted from heartwood, but consisted of more ingredients than those in heartwood, mostof which were saturated hydrocarbon, saturated aldehyde and eighteen-carbon skeleton acid.Average oil content of sapwood was1.61%.(3)No significant differences of total santalene content (p=0.992) and sesquiterpenehydrocarbon content (p=0.982) were found between sapwood and heartwood, but thedifferences on total santalol content (p<<0.001) and sesquiterpene alcohol content (p<<0.001)were great. Santalols and sesquiterpene alcohols isolated from heartwood were higher incontent than those isolated from sapwood, while teresantalol content in heartwood was lowerthan those in sapwood (p<<0.001).(4)Large-scale sandal plantations had good growth in southern China, about15~20%ofthe individuals started to form heartwood naturally as early as6-year old, but the oil content inthese young sandals was low, which ranged from0.66%to1.76%. Essential oil compositionwas similar with that extracted from mature sandals, but the content of α-santalol andβ-santalol were low, which account for20.19%and10.14%in average respectively, the qualityof oil did not meet with the current ISO standard for sandal oil.(5)Heartwood in young sandal could be induced by stem gas filling, but the amount ofheartwood induced by different gas treatments was significantly different (p<<0.001). The areaor amount of induced heartwood above/below the drill hole was as the following order:nitrogen> carbon dioxide> ethylene=wounding. Treatment with ethylene had the highest oilcontent of17.11%in average among all treatments (p=0.001), which was far beyond thenormal oil content of sandal, but α-santalol content and β-santalol content were relative low,only31.05%and12.67%in average respectively；Ingredient analysis showed that essential oilextracted from heartwood induced by ethylene contained some polyphenols, extractives andother non-santalol substances. Treatment with carbon dioxide had the highest content ofα-santalol and β-santalol, which were41.09%and18.91%in average respectively, and oilquality met with the current ISO standard for sandal oil, which means that carbon dioxide mayplay an important role in induction heartwood formation of sandal. (6)Heartwood in young sandal could be induced by stem injection of chemicals, and nostatistically differences were found in term of heartwood amount (p=0.457) between differentchemical treatments and the corresponding concentrations; Stem injection of0.3%ethrel hadcaused great damage on PSII of young sandals, as a result, light use efficiency was reducedsubsequently, and net photosynthesis rate was decreased significantly (p<<0.001); Steminjection of0.6%benzyladenine had the highest oil content in the induced heartwood (9.34%in average) among all treatments (p<<0.001), followed by0.3%ethrel and0.3%jasmonic acid(both were5.33%in average); treatment with0.15%paraquat had the least oil content amongall treatments, only2.54%in average.(7)Oil quality of heartwood induced by low concentration of ethrel (0.3%), lowconcentration of jasmonic acid (0.3%) and high concentration of paraquat (0.3%) met with theISO standard for sandal oil, but both concentrations of benzyladenine (low referred to0.3%and high referred to0.6%) caused young sandals to form qualified oils which meet with thecurrent ISO standard for sandal oil, this indicated that benzyladenine could play a key roleduring heartwood formation of sandal.(8)Stem inoculation of fungi could induce heartwood formation in young sandals, and thearea or amount of heartwood induced by different fungis was statistically different (p<<0.001).The area or amount of induced heartwood above/below the inoculation drill was as thefollowing order: Botryosphaeria rhodina> Fusarium spp> Colletotrichum gloeosporioides>Khuskia spp=C.K. Inoculation of Khuskia spp got the highest oil content among all treatments(p=0.032), which are7.74%in average. Many non-santalols and unidentified or unisolatedsubstances were found in essential oil which extracted from heartwood induced by fungi, as aresult, α-santalol content and β-santalol content were relative low so that oil quality could notmeet with the current ISO standard for sandal oil. Therefore, stem inoculation of fungi ininduction heartwood formation of young sandals was not so practical.(9)Differences on water content and basic density of sandal heartwood induced bydifferent treatments (include gas filling, chemical injection and fungi inoculation) were not significant, which indicated that some properties of sandal heartwood were unsesceptible totreatments or stresses, and maintained in a cetrain range.(10)It seems that sandal heartwood formation and senescence were two independentprocesses with little connection, but harmone imbalance could have great influences on forcingheartwood formation of young sandal.
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