Re: Which plant cell structure is most similar to a brain cell?

Dear Dawn,

Probably the most important brain cells are neurons, the primary function of which is to conduct electrical impulses.  This is accomplished by voltage-gated ion channels, which open & close in rapid succession to transmit this "action potential" along the length of the neural cell membrane surface, as described by the section on Things Ion Channels Do, in the Ion Channels for Beginners: The ABCs of Ion Channels tutorial from Montana St. Univ.  These ion channels are composed of an electrogenic Sodium-Potassium ATPase Pump, as illustrated nicely in this diagram from the Univ. of Minn.

This action potential often originates in response to a sensory stimulus, such as touch or light.  As described in this Plant Sensory Systems webpage from the NASA/NSF Research Network, plants also respond to sensory stimuli, including light, mechanical (touch), gravity, & heat.  Although the mechanisms of these responses have not yet been completely characterized, alterations in membrane potential associated with electrogenic ion transport appears to play a role here, as well.  The exact nature of these ion pumps may differ somewhat from that of neurons, especially since it is known that proton pumps are more common in plants, bacteria, & fungi than the sodium-potassium or calcium pumps of animal neurons, as described briefly in these Membrane Structure & Function lecture notes from Georgia Perimeter College.  However, it is noteworthy that calcium channels appear to play a role in at least the gravitropic response of plants, and sodium-potassium ion channels may be responsible for regulating the opening & closing of plant stomata in response to water availability.  So plants & animals may ultimately have more in common with respect to ion channel structure & function than previously suspected.

In summary, those plant cells that respond to sensory stimuli appear to utilize ion channels to transmit this response in a manner very similar to that in which neurons respond to sensory stimuli.  The main difference would appear to be that these responses are not assigned to a specialized organ or system, such as the brain & the nervous system, but are, instead, a function of many, if not all, cells in any individual plant organ, such as the leaf.  Another inherent difference is the presence of cell walls in plants, which prevents the use the synaptic-type intercellular signaling of neurons.

Nevertheless, ion channels appear to be a common "cell structure" in both plant & brain cells.  For more detailed info., please see Types of Ion Channels Known or Ion Channel History in the Ion Channel Primers from Montana St. Univ.

I hope this satisfies your requirements, as it's the only similarity that I could come up with.  Thanks for the challenging question,

Jeff Buzby, Ph.D.
CHOC Research Inst.
MadSci Cell Biology Network