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 causes an action potential to be triggered on the postsynaptic side – further encouraged by low internal sodium of the principal neurons. In the mature calyx, the AMPA receptors are concentrated on the principal neuron as to localize the transmission for greater action potential probability. Also note, the NMDA-type glutamate receptors contributions decrease after the onset of hearing. The mechanism behind synaptic vesicle endocytosis changes as the calyx becomes more mature. Calmodulin and calcineurin in their active form are required for vesicle endocytosis in an immature calyx; however, in the mature calyx neither calmodulin nor calcineurin are necessary. Rather, the