calyx, stem
蔕 centers on the base part of a plant where the fruit or flower attaches: the calyx or stem end. Both given meanings describe this same connecting structure.
蔕 combines 艹 (grass/plant) with 帶, which likely contributes the sound and the idea of a belt or band, suggesting the part that ties the fruit to the plant.
The grass top 艹 sits above 帶, which looks like a belt or band. Picture the calyx as a tiny green belt holding the fruit onto the plant stem.
For テイ, imagine a tea stem: the small stem of a tea leaf is the calyx. Tea -> テイ, and the stem holds the leaf.
calyx