Stigma (botany) Stigma (botany) The stigma (plural: stigmata) is the receptive tip of a carpel, or of several fused carpels, in the gynoecium of a flower. The stigma, together with the style and ovary comprises the pistil, which in turn is part of the gynoecium or female reproductive organ of a plant. The stigma forms the distal portion of the style or stylodia. The stigma is composed of , the cells which are receptive to pollen. These may be restricted to the apex of the style or, especially in wind pollinated species, cover a wide surface. The stigma receives pollen and it
Calyx of Held high frequency sound localization. This synapse has been described as the largest in the brain. The related endbulb of Held is also a large axon terminal smaller synapse (15-30 µm in diameter) found in other auditory brainstem structures, namely the cochlear nucleus. As with the calyces, these synapses promote fast, efficient information transfer. The calyx of Held holds vesicles containing glutamate on the presynaptic terminal, the vesicles are released upon stimulation (originating in the auditory system). The glutamate then binds to two known glutamate receptors, AMPA- and NMDA receptors. Commonly used in research due to its large size, the calyx