Doubly guaranteed mechanism for pollination and fertilization in Ipomoea purpurea.

Flowers, the reproductive organs of angiosperms, show a high degree of diversity in morphological structure and flowering habits to ensure pollination and fertilization of plants. Effect of flower movement on pollination and fertilization was investigated in Ipomoea purpurea (Convolvulaceae) in this study. Fluorescence microscope was used to observe the germination of pollen grains at different temperatures. From 4:00 am to 6:00 am, the stigma was taller than the filaments so that self-pollination had no chance to be completed and cross-pollination was carried out by insects. Pollen grains germinated rapidly after falling on the stigma, the pollen tube reached the ovule to complete the fertilization after 2-3 h. From 7:00 am to 9:00 am, filaments of two stamens grew rapidly and reached the same height as the stigma to allow self-crossing. But at this time, the natural temperature was already high and not conducive to the germination of pollen grains. The corolla formed a closed inverted bell-shaped corolla, where the inner microenvironment ensured the completion of pollen germination and fertilization. Preferential cross-pollination and delayed self-crossing of I. purpurea provided a doubly guaranteed mechanism for pollination and fertilization, allowing its adaptation to high temperature climate.