2017 Volume 16 Issue 2 Pages 125-130
In order to grow Habenaria radiata (Thunb.) K. Spreng. seedlings in their natural habitat, they must be pollinated by insects (natural crossing) and form numerous seeds. We investigated the rates of capsule formation and seed germination in H. radiata in a natural habitat in Aichi Prefecture. Seed capsule formation and the germination rate of the formed seeds in H. radiata individuals growing in their natural habitat were widely altered. Subsequent investigations of the factors affecting seed germination rates revealed that H. radiata germination was not affected by the nutrient status. The presence of relatively few H. radiata pollinators in the study area was considered to be responsible for the low pollination rate. In addition, the rates of seed capsule formation and germination varied markedly depending on the timing of pollination (days after anthesis: DAA), with the highest rates of capsule formation and germination observed when pollination occurred in the middle term of flowering at 4 to 5 DAA. These findings suggest that H. radiata flowers are the most susceptible to pollination at 4 to 5 DAA, and that pollination by insects during this period results in the formation of capsules containing the most viable seeds.
