Development of the endophytic parasite, Rafflesia patma Blume, among host plant (Tetrastigma leucostaphylum (Dennst.) Alston) vascular cambium tissue

Abstract The early life history of Rafflesia R.Br. is hidden by its cryptic nature. Being a holoparasitic plant, early growth and development of species in this genus have been suggested to occur inside the host plant. In this study, using microscopic analyses, we examined how Rafflesia patma Blume grows from a simple clump of cells or protocorm inside the cambium tissue of Tetrastigma leucostaphylum (Dennst.) Alston, its host plant. We further show how the protocorm expands in about 2 months into an early form of a flower knob or bud, just before the flower begins to emerge from the host plant vine. Our study suggests that the endophyte, R. patma , spreads within T. leucostaphylum vascular cambium tissue in a linear manner, but not as a continuous strand. We suspect that the parasitic endophyte spreads inside the host vascular cambium and is pushed farther away from its point of origin to another part of the host as the host vine cambium fusiform initial cells divide and enlarge over months. Moreover, the protocorm matures in the cambium region of the T. leucostaphylum vine which lies close to the xylem, and grow outwards, bursting through the host phloem, then the host cortex, and finally towards the host periderm as it begins to emerge. Although we believe this might be the closest prediction on how Rafflesia develops at an early stage and is distributed within its host body, a future analysis of endophytic tissue growth in a controlled environment, such as the use of tissue culture, is required to strengthen our findings.
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