Dampak Serangan Patogen Kanker Batang Terhadap Struktur Anatomi Kayu Dari Pohon Karet (Hevea brasiliensis Muell. Arg) Bekas Terbakar Di PT Inhutani I Batu Ampar

Abstract

The objectives of the research were to determine the effect of pathogen stem canker on the burnt rubber wood anatomy (Hevea brasiliensis Muell. Arg.) included the causal agent, symptoms and rate of wood decay. The research resulted that the canker occurred locally at the area of fire injury directed from base to upright of the stem. Symptoms of the canker were opened xylem, callus formation which could not fully covered the xylem causing malformed stem, splitting, pelled and uneven floem around the canker. The causal agent of the canker was a species of white rot fungus belonged to the class Basidiomycetes. The fungus infected the rubber wood and the hyphae could be found outside (intercellular) and inside the woody cell cavity (intracellular). The hyphae infected through pith, perforation side and degraded cell wall enzymatically. Response of the tree against the fungus attack was deviation of wood in the form of callus formation, inserted floem, smaller pores of xylem adjacent to the callus, deviation of ray direction and formation of decay zone with abundant pores filled with tylosis and gum, barrier zone consisted of pores filled with gum, active and inactive cambium zones respectively showing an area of wood formation before and after fire. The lower rate of wood decay in transversal section indicated the tree formed defense vessels to avoid expansion of the fungus in other vessels. The characteristics of wood were also changed, i.e. wood colors were changed from dark brown to light brown or pale and whitish, wood textures were changed from smooth to rather rough till extremely rough, fibre direction changed from straight till interlocked grain to wavy, wood surface changed from medium to extremely rough and the hardness of wood reduced till soft and rotten. The attack of fungus on xylem formed before fire was not significantly affected the change of dimension and number of cells. Significantly difference between xylem infected by fungus before fire and xylem without infection after fire and also xylem at the top of the tree caused by reaction of the tree in the effort of covering injury at the canker area by forming callus and defense vessels such as pores and axial parenchyma contained with gum to avoid expansion of the fungus in order to distribute food to the whole parts of wood needed for the growth of the tree continuously. From the results it can be suggested that burnt rubber wood infected by fungus growing on the unfertile area should be cut as soon as possible, because wood deterioration will be extended when it is too long exposed to the opened area without ability to cure naturally. Based on the anatomic structures of burnt rubber wood infected by the fungus, it is indicated that the wood still usable, however to determine how far are the value and utility, it is needed further researches, mainly about the change of wood characteristics chemically, physically and mechanically. Observations on the characteristics of the fungus are needed to find out method of control.