Localized Effects of Mechanical Wounding and Exogenous Jasmonic Acid on the Induction of Secondary Laticifer Differentiation in Relation to the Distribution of Jasmonic Acid in Hevea brasiliensis

The relationship between the effect of exogenous jasmonic acid (JA) on the induction of secondary laticifer differentiation and the distribution of JA in the seedling of Hevea brasiliensis Mull. Arg. was investigated with the aid of experimental morphological and radioisotope technique. Most radioactivity of H-3-JA sustained in treated site within one hour while no radioactivity was detected in new shoot and the radioactivity in upper leaf was much less than that in the parts below the treated site, suggesting that JA was mainly transported downwards in the shoot of H brasiliensis. Mechanical wounding hindered the entrance of exogenous JA remarkably while held back the entered JA to the regions around wounded site. The effect of exogenous JA and mechanical wounding on the induction of the secondary laticifer differentiation was limited to treated site where high level of JA was expected. Mechanical wounding reduced the effect of exogenous JA on the differentiation of secondary laticifer, which could be ascribed to the hindrance of mechanical wounding to the entrance of exogenous JA. It was concluded from the combined data that a high accumulation of JA was required for inducing the secondary laticifer differentiation in H. brasiliensis.

The secondary laticifer differentiation in rubber tree is induced by trichostatin A, an inhibitor of histone acetylation

The secondary laticifer, a specific tissue in the secondary phloem of rubber tree, is differentiated from the vascular cambia. The number of the secondary laticifer in the trunk bark of rubber tree is positively correlated with rubber yield. Although jasmonates have been demonstrated to be crucial in the regulation of secondary laticifer differentiation, the mechanism for the jasmonate-induced secondary laticifer differentiation remains to be elucidated.By using an experimental morphological technique, the present study revealed that trichostatin A(TSA), an inhibitor of histone deacetylation, could induce the secondary laticifer differentiation in a concentrationdependent manner. The results suggest that histone acetylation is essential for the secondary laticifer differentiation in rubber tree.

Relationship between the number of tapping-induced secondary laticifer lines and rubber yield among Hevea germplasm

The lack of suitable early selection parameters means that traditional rubber breeding for yield is time consuming and inefficient. Laticifer is a tissue specific fo natural rubber biosynthesis and storage in rubber tree. The number of the secondary laticifers in the trunk bark tissues is positively correlated with rubber yield in the matured rubber trees that are regularly tapped. In the present study the rubber yield from 280 of 4–5 year-old virgin trees from7 cross combinations was compared with the number o newly differentiated secondary laticifers caused by tapping. Results showed that the number of tapping induced lines of secondary laticifers varied in differen germplasm and was positively related to the rubber yield indicating this could be used as a suitable parameter fo early evaluation of yield potential of rubber trees.