Abstract:

Objective: This study explored the effects of different combinations of inorganic salts and hormones induced to agarwood and its mechanisms in Aquilaria sinensis, with the aim to effectively promote agarwood formation. Method: Uniform test design was used to deal with ten-year-old trees. NaCl, FeSO₄, CaCl₂, methyl jasmonate and ethephon were selected as the induction factors, and each factor covered 3 levels, totally 5 induction treatments. The content of starch, soluble sugar, alcohol soluble extract and the discoloration range of stem wood were determined, and histochemical and inclusion changes were, respectively, observed by optical microscopy and scanning electron microscope(SEM) through wood core samples that taken 0.5, 1, 3, 6, 10 months after treated. Result: 1) With the increase of induction time, the content of starch firstly decreased and then increased, and the time to reach to the lowest value was different between different treatments. While the content of soluble sugar was opposite, which firstly increased and then decreased, and the peak values were reached all at the 6th month. 2) It was found that the content of lipid substance in the ray cells, axial parenchyma cells and vessel of each treatment increased with time. 3) Wood parenchyma tylosis accumulated into adjacent vessel through half bordered pit between the vessel and parenchyma cells until complete blockage. 4) The effect of each treatment on the lateral discoloration range of wood core was not significant, but the length of the longitudinal discoloration was longer. The longitudinal discoloration length of treatment 2(0.5%NaCl+1.5%FeSO₄+0.1%CaCl₂+0.01%methyl jasmonate +0.05%ethephon)reached 77.0 cm after 10 months of induction. 5) The content of alcohol soluble extract increased with time, and the differences between different treatments were significant. Conclusion: 1) Among the five induction treatments, the optimal treatment was 0.5%NaCl+1.5%FeSO₄+0.1%CaCl₂+0.01%methyl jasmonate +0.05%ethephon, and the content of alcohol soluble extract reached 19.07% after 10 months of treatment. 2) NaCl and ethephon were the main factors to promote the aloes yield, and ethephon played a leading role. Theoretically, the optimum combination of agarwood induction was 0.16%NaCl+0.21%ethephon. 3) The lipids were firstly formed in parenchyma cells and then accumulated in vessel and parenchyma cells. The accumulation of lipids in the vascular was related to the changes of starch content in the parenchyma cells, the stronger the ability of starch transformed to soluble sugar, the more lipid accumulated and the more favorable for agarwood formed.

Key words: Aquilaria sinensis, inorganic salts, hormones, agarwood formation