Source Year: 2015

Number of secondary laticifers differentiating from vascular cambium have significant positive correlation with the rubber yield of Hevea. Secondary laticifer does not appear in the stem of the first and second extension unit (EU) of Hevea brasiliensis shoots under natural conditions. It can be induced by mechanical wounding or jasmonic acid (JA) treatment in these parts. Season obviously influences the socondary laticifer differentiation induced by mechanical wounding or JA. In the present paper, the relationship between cytokinin content, vascular cambium activity and effect of mechanical wounding or exogenous JA on the secondary laticifer differentiation in the stem of H brasiliensis shoots were revealed. The results of the experiment showed that vascular cambium were active from March to October and dormant from November to the following February in the stem of epicormic shoots of H brasiliensis. Accordingly, the content of isopentenyl adenosine (IPA) in bark tissues was much higher in July than that in January. Either JA or mechanical wounding could induce the secondary laticifer differentiation in July, but neither of them was effective in January. Combination of JA with 6-benzyl aminopurine (6-BA) was quite effective on the secondary laticifer differentiation in January while less effective in July. It is suggested that appropriate ratio of JA to cytokinin is pivotal in regulating the secondary laticifer differentiation in H brasiliensis.