Host-parasitic relationships between Tetrastigma rafflesiae and Rafflesia cantleyi and R. azlanii in Belum-Temenggor Forest Complex, Perak, Malaysia / Syarifah Haniera Sheikh Kamal

Rafflesia is a holoparasite plant that depends solely on its host to get the nutrients where at early stage this parasite is living inside the host vine. For that reason, life cycle of Rafflesia is very complex because it involves the invisible and visible parts of its growth. Currently, there is little information on the life cycle of Rafflesia, therefore knowledge regarding its life cycle is crucial for a successful monitoring of the species as part of conservation efforts. The objectives of this study were to analyse the growth of flower buds at various developmental stages of Rafflesia cantleyi and R. azlanii and to identify anatomical characterization of host-parasite relationships between T. rafflesiae and R. cantleyi and R. azlanii. The growth rate of R. azlanii and R. cantleyi were observed monthly for five months beginning from an emergence of buds to full bloom in the study sites of Belum-Temenggor Forest Complex, Perak. The buds were measured and vertically photographed for every observation and categorized into eight stages. The anatomical observation study consisted of three stages of Rafflesia buds namely cupule stage, cupule-bract transition stage and bract stage attached with the host. All samples were undergoing paraffin wax technique and were observed using light microscope (LM) and scanning electron microscope (SEM). R. azlanii buds have grown at the mean rate of 0.20 cm/day and for R. cantleyi was 0.26 cm/day. This suggests that R. azlanii exhibited a slower growth rate than R. cantleyi. In addition, the mortality rate of R. azlanii was lower than R. cantleyi (i.e., 28% vs 45%, respectively). Meanwhile, the life cycle for visible stage of R. azlanii was 14 months and 11 months for R. cantleyi. Based on the anatomical observation, at the cupule stage of R. azlanii bud showed three parts of flower tissue that resulted formation of several types of meristematic cells in early bud of Rafflesia. The bud structure for cupule-bract transition (CBT) stage and bract stage were not clearly seen for both species due to the ruptured cells during sectioning process. Nevertheless, the parasitic intrusion of both Rafflesia species has shown a pointed tissue towards the host, T. rafflesiae, which may involve in minimising the damage to the host plant. The information gathered from this study is useful for field monitoring and observation of the plants for the conservation purposes.