Plant parasite of plants

One of our students defended her master's thesis today, and it was a very impressive study designed to see if a plant parasite responds to a host plant under water stress like insect herbivores would respond.  The parasite is an amazing organism, dodder, a fully parasitic vine in the morning glory family.  It looks like yellow-gold silly string, and it can make some really impressive infestations.  One of the hardest problems is keeping a single parasite on a single host, and in nature the vine can sprawl across numerous hosts and make hundreds of connections to the vascular tissues of the host plants.  It turns out that dodder doesn't react like aphids or other herbivous insects, but it is a totally amazing organism none-the-less. Image courtesy of Silvae.

Plants deep in thought?

Well, something is deep. Heidi Marshall finds

it absolutely fascinating that scientists are finally starting to consider plant sentience a serious possibility. The idea of plant communication is not entirely new, and has been an integral part of some spiritual practices. So, if plants are capable of communicating with each other, and understanding whether those around them are family or not, can they also feel pain? And if they can feel pain, do their relatives hear their screams when they are cooked or eaten? I think the idea of plant sentience may put a whole new perspective on things for some people. It would seem that if plants are capable of the same things as animals (realization and communication), that eating a carrot would be no different than eating a chicken leg, as both come from beings that display awareness. It certainly gives you something to think about.

What a great example of anthropomorphic thinking. This isn’t new; consider the legends surrounding mandrake, whose name is basically a synonym of anthropomorphic, but nothing about plant communication suggests plants have any such higher animal attributes. Plant communication is not equal to plant sentience; organisms can “communicate” without having any awareness in the usual sensory sense of the word because plants don’t have sense organs or a nervous system, so the concept of pain seems misplaced as well. Seriously, do you actually think a head of cabbage screams in pain as you colely slice it into slaw? Sorry but that's just cabbage-headed. Does a plant grow toward the light because it “loves” the feeling? Do roots grow down because they enjoy the tug of gravity? Is the color yellow happy? When you google plant sentience, you will notice one interesting thing. The people discussing this idea are not botanists or horticulturalists.
Part of the problem is the semantic baggage associated with words like “communication”. Plants react to stimuli, and some of those stimuli are molecular plant signals. Dodder is a parasitic vine that “tastes” its hosts and grows such that it can find and put more parasitic taps into better hosts, but it isn’t thinking yummy thoughts (see this link for some images and a similar discussion). Why do reasonably smart people engage in so much new-agey fuzzy thinking? Taking concepts like sentience and expanding it to a concept where it is synonymous with being alive, i.e., capable of reacting to a stimulus, doesn’t help anyone understand anything. If ever there were a group of people with this problem it’s the founders of the Society for Plant Neurobiology, a new discipline with nothing to study but plant signaling, and plant physiologists and cell biologists were already doing that, and many chided their colleagues for using “superficial analogies and questionable extrapolations”. The use of such terms as plant neurobiology must be regarded as an attempt to make more of a phenomenon than it presently deserves, and it doesn’t assist with the public’s understanding of science one tiny wit as Heidi so well demonstrated. The Phactor has spoken at length with my pal Phil O'Dendron, but he hasn't had much to say, and that says a lot.