Overview
This lecture covers the biology, parasitic lifestyle, pollination, and seed dispersal mechanisms of Rafflesia arnoldii, highlighting its unique adaptations and scientific mysteries.
Rafflesia: General Characteristics
- Rafflesia is a genus with over 30 species found in Southeast Asia's tropical forests.
- The largest Rafflesia flower weighs seven kilograms and measures over a meter wide.
- Rafflesia is known for its foul smell, which resembles rotting flesh.
Parasitic Lifestyle and Adaptations
- Rafflesia is a parasite, spending most of its life as an endophyte embedded in its host.
- It infects only Tetrastigma vines, which contain energy-producing chloroplasts.
- Rafflesia lacks roots and cannot photosynthesize, relying entirely on the host for water and nutrients.
- The plastids of Rafflesia have lost their DNA and photosynthetic ability.
Horizontal Gene Transfer (HGT)
- Rafflesia has acquired genetic material from its host and other plants via horizontal gene transfer.
- Parasitic plants like Rafflesia use some of these stolen genes for key cellular processes.
- HGT is common in bacteria, but rare and recently documented in parasitic plants.
Flowering and Pollination
- Rafflesia emerges from the vine as a bud and can take up to a year to bloom.
- The flower's smell attracts carrion flies, which are vital for pollination.
- Rafflesia flowers are either male or female; cross-pollination depends on flies carrying pollen between flowers.
- The massive size and strong odor help attract pollinators through dense rainforest air.
Seed Formation and Dispersal
- After pollination, the flower withers as fruit containing thousands of seeds develops.
- The exact agents of seed dispersal are unknown; possibilities include elephants, rodents, and ants.
- Seeds have an oily elaiosome that attracts ants, but their fate inside ant nests is unclear.
- No one has observed Rafflesia seeds germinating or infecting host roots.
Conservation and Research Challenges
- Difficulty in cultivating Rafflesia from seeds outside its native habitat impedes research.
- Loss of rainforest habitat threatens Rafflesia and scientific understanding of its life cycle.
Key Terms & Definitions
- Endophyte — an organism that lives within a plant for part of its life.
- Chloroplast — an organelle in plant cells that carries out photosynthesis.
- Horizontal Gene Transfer (HGT) — movement of genetic material between unrelated species.
- Elaiosome — an oily appendage on seeds that attracts ants for seed dispersal.
Action Items / Next Steps
- Review mechanisms of plant parasitism and HGT.
- Read about pollinator deception in other plant species.
- Prepare for discussion on conservation strategies for rare parasitic plants.