Host-Parasitic Relationships between Tetrastigma rafflesiae and Rafflesia azlanii and Rafflesia cantleyi in Belum-Temenggor Forest Complex, Perak, Malaysia

Abstract

Rafflesia is a holoparasitic plant that depends solely on its host for its nutrients, given that during the early stage of its life, this parasite lives inside the host vine. The lack of host specificity and preference information for Rafflesia can largely be attributed to the absence of a comprehensive taxonomic study in Tetrastigma . Without the host, the Rafflesia will not be able to survive. Therefore, this research was conducted to study the host-parasitic relationships between the two species using anatomical dissection and micrographic images using a light microscope (LM) and scanning electron microscope (SEM). The anatomical study consisted of three stages of Rafflesia buds; the emergence of cupule stage, cupule-bract transition stage, and bract stage ­­attached with the host. All samples underwent sliding techniques and were observed using LM and SEM. Based on the results, the anatomical characteristics of the host-parasite for the cupule stage evidenced penetration of the parasite-affected tissues inside the vascular bundles with the visibility of the flower bud. However, during other stages, the penetration of parasite-affected tissues to the vascular bundles was disrupted and cannot be seen using this sliding technique. The endoparasite of Rafflesia invades the host only towards the phloem region in the early stage. In contrast, in late buds for both species, the Rafflesia tissue invaded both the host xylem (proximal region) and phloem. The parasite intrusion movement for both Rafflesia species showed a pointed tissue towards the host as this was believed to minimise the damage of the host plant. A new method using the paraffin wax technique might improve the sectioning and provide a more precise relationship dissection. The information from this study is expected to provide baseline information and an understanding of the host-parasitic relationship between the species. In addition, further anatomical studies with the different stages of buds will offer a better understanding of their relationship with the host.