RELATIONSHIPS AMONG YIELD, GIRTH AND SOME STRUCTURAL CHARACTERS OF THE LATICIFEROUS SYSTEM IN YOUNG SEEDLINGS OF RUBBER TREES (HEVEA)

The aim of the present investigation was to examine the relationship b etween growth, yield and characters of the laticiferous system of seed lings at the nursery stage. The main objectives were to seek informati on concerning the extent these characters are independent of each othe r and establish among the studied characters the principal ones that d etermine the yield. Thirty seedlings at the nursery stage of [Hevea br asiliensis (Willd. ex Adr. de Juss.) Muell.Arg.), with yield levels ra nging from high to low, were evaluated for juvenile growth (G), yield (Y) and bark structural characters to identify early selection paramet ers. The bark structural characters studied were: bark thickness (BT), total number of latex Vessel rings (LV), overall density of latex ves sels per ring per five square millimeters of bark (DV), average diamet er of latex vessels (DL) and average distance between consecutive late x vessel rings (AD). The results showed significant linear correlation s between Y and LV or DV. No correlations were detected, however, betw een Y and G or BT. The correlations between G and BT were positive and significant. Multiple regression studies of Y on DV, LV, DL, BT and G suggest that DV and DL, through non-significant, jointly accounted fo r 49% of the variation on Y. When G was used as the dependent variable , with BT and DV as independent variables, BT was the only important a nd significant variable, accounting for 41% of the variation on G. Stu dies of LV on AD or Y, shows that AD and Y were the dominant and signi ficant variables accounting for 39% and 17% of the Variation in LV. Gi rth and bark thickness do not appear to give significant positive pred ictive power for LV.