The objective this work was to compare the frequency of the laticifers of the primary system with the number of laticifer rings in young plants of seedlings and clones of rubber tree (Hevea spp.), in order to better understand of early yield tests. It was found a low frequency of primary laticifers in the first four internodes of seedlings while a frequency significantly higher of this type of laticifer was found in the clones, from the first to the fourth internode. Since the primary system of laticifers is originated in the subapical meristem, the observed differences are determined by the size of the apical bud. It is more than three times larger in the first whorl of clones than in the first whorl of seedlings (epicotyls) and it is also significantly larger in the second whorl. The main rubber production analyzed in the early tests in plants of clones one year old is therefore derived from the laticifers of the primary system, sloughed off in plants older more than three years. This fact explains the lack of correlation between the early test of clones and the HMM test in plants three years old. On the other hand, this correlation has been reported for the early test of seedlings and the HMM test for three years old clones.
apical bud; subapical meristem; early tests; HMM test
