Abstract
Oleoresin from Pinus merkusii is one of the most important forest products in Indonesia. The objective of this study was to examine the effects of various stimulants and environmental factors on oleoresin yield. The first factor was the stimulant treatment, i.e., SAEt1 (20% sulfuric acid + 1% Ethephon); SAEt2 (20% sulfuric acid + 2% Ethephon); SR4 (mainly composed by sulfuric acid); ETRAT (mainly composed by ethylene and citric acid); and without stimulant spraying. The second factor was the site with different altitudes, i.e., West Banyumas (326 m asl), East Banyumas (797 m asl), and West Pekalongan (1150 m asl). Through analysis of variance, the relation between stimulant and site was highly significant in regards to the average daily oleoresin yield. The results indicated that the combination of sulfuric acid and Ethephon increased oleoresin production 1.69- to 2.85-fold compared with untreated trees, depending on the sites. The trees with SAEt1 and SAEt2 treatments yielded an equivalent amount of oleoresin compared to that of trees exposed to the SR4. The ETRAT showed the lowest resin yields compared to the other stimulants. The values of daily relative humidity and temperature did not show similar responses in all sites when correlated with daily oleoresin yield.
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