Pappus (botany) Pappus (botany) The pappus is the modified calyx, the part of an individual floret, that surrounds the base of the corolla tube in flower heads of the plant family Asteraceae. The term is sometimes used in other plant families such as Asclepiadaceae (milkweeds), whose seeds have a similar structure attached, although it is not related to the calyx of the flower. The Asteraceae pappus may be composed of bristles (sometimes feathery), awns, scales, or may be absent. In some species, the pappus is too small to see without magnification. In species such as Dandelion or "Eupatorium", feathery bristles of the
Calyx of Held sensitivity. Both low-threshold K channels and high-threshold delayed rectifier-type K channels are present in presynaptic neurons. There are four low-threshold K channels present: K1.1, K1.2, K1.3, and K7.5. K1.1 and K1.2 are located in the transition zone between the axon and the terminal, while K1.3 K7.5 are located in the calyx. There is a calcium activated potassium channel expressed in the calyx, however this type of channel does not contribute to neurotransmitter release. Within the span of one week, mice subjects (P7 to P14) showed that the density of the K1 and K3 low threshold channels increases, which in turn