Pollination biology of Pongamia pinnata (L.) Pierre: a potential biodiesel plant

Pongamia pinnata, is an important biodiesel plant in India. The seed is an economic part of the plant used for extraction of biodiesel. The reproductive biology of P. pinnata is important for determining barriers in setting pods. The study has been carried out at Central Agroforestry Research Institute, Jhansi, India, during 2017–2019. The observations were made on the floral biology and pollinator activity in P. pinnata for 2 years. Anthesis was noticed between 0800 and 1000 h with peak anthesis between 0800 and 0830 h. Flower longevity was only 1 day. Pollen dehiscence occurred 1–2 h before anthesis. Pollen remained viable throughout the day with maximum germination (96.15%) coinciding anthesis time. Whereas, maximum pollen tube length (0.54 ± 0.10) was observed during 1000 h. Stigma remained receptive for 8 h after anthesis, the maximum receptivity was noticed 2 h after anthesis (82% of pollen germination) and it was coinciding the time where maximum pollen tube length recorded. The style was longer than stamens, indicating that the flower appeared to be adapted for cross-pollination. There were 13 flower visitors recorded, of which Megachile species were more abundant compared to Apis, Xylocopa species and, other flower visitors. The pollinator exclusion experiment was conducted to assess the role of flower visitors on pollination and fruit set. No pod set was noticed in the absence of insect pollinators. Whereas, in an open-pollinated condition, pod set ranged between 15 to 18%.