Plant Intranet Seen in Action
How do roots respond to what the top of the plant experiences? With an elaborate communication system resembling email.
The authors of a paper in Science Magazine don’t use the words email or intranet, but the signaling system they describe fits that description:
Nitrogen (N) is a critical nutrient for plants but is often distributed unevenly in the soil. Plants therefore have evolved a systemic mechanism by which N starvation on one side of the root system leads to a compensatory and increased nitrate uptake on the other side. Here, we study the molecular systems that support perception of N and the long-distance signaling needed to alter root development. Rootlets starved of N secrete small peptides that are translocated to the shoot and received by two leucine-rich repeat receptor kinases (LRR-RKs). Arabidopsis plants deficient in this pathway show growth retardation accompanied with N-deficiency symptoms. Thus, signaling from the root to the shoot helps the plant adapt to fluctuations in local N availability.
These small peptides, in other words, provide information sent from the roots to the growing shoots at the top of the plant. But that’s not all; the shoot responds to its email with a message back down to the roots. Bisseling and Scheres describe this communication network in a Perspective article in Science:
Therefore, plants integrate local and global nutrient cues to spend resources efficiently. On page 343 in this issue, Tabata et al. (1) identify a peptide signaling mechanism by which the root locally senses N limitation in the soil, and communicates with the shoot, which then signals back to the root to stimulate lateral root growth in regions with a high nitrate content to facilitate nitrate uptake.
The system presupposes that cells in the shoot can “read” the peptide, understand it, and respond appropriately. Ditto for the reader down underground.
Scientists cannot yet “read” the email messages. “The nature of the signal from the shoot that triggers lateral root foraging behavior in the +N compartment remains to be resolved,” Bisseling and Scheres state. But like watching two parties communicate in a foreign language and then respond with actions, the scientists can tell that communication is occurring. It’s not sentient communication, as with human verbal communication. It’s more like computer language: preprogrammed, digital, and responsive. A designer would look at this and say, “Aha!”
From an engineering perspective, it makes perfect sense to decide centrally (in the shoot) whether the overall nutrient status is adequate, and then send systemic signals to stimulate growth everywhere except where the local inhibition system is active.
The Japanese team provides more evidence of an intranet. The system looks like one office communicating both with itself and with distant departments of the company:
Nitrate uptake systems are under control by both cell-autonomous local signaling triggered by nitrate itself and systemic long-distance signaling that transduces external and internal N status across spatially distant root compartments.
By blocking the return email, the researchers figured they could learn whether the signals are necessary. Indeed, they were. By mutating the CEP gene that codes the emails, the plants became nitrogen starved. “These phenotypic and transcriptional analyses suggest that CEP signaling is likely to underlie N starvation responses and, accordingly, its overactivation or blockage leads to pleiotropic developmental effects in both roots and shoots.”
This is another example of intra-plant communication that has been coming to light over the last few decades. “Small molecules such as secreted peptides can mediate long-distance signaling,” the authors say. The peptide messages, moreover, are preprogrammed in DNA: “The genes that encode small peptide signals are often parts of large families of genes with overlapping and redundant functions.”
Although they tested their hypothesis with a lab plant, the system they described is operative throughout the plant world. This means that a needle on a giant redwood hundreds of feet in the sky is capable to communicating, in principle with its roots underground. A plant may not be able to walk around, but its intranet and email system gives it a sophisticated way to respond to changing conditions in a holistic way:
Plants, as sessile organisms, continuously face a complex array of environmental fluctuations and have evolved sophisticated responses to cope with them. Given that CEP family peptides are conserved throughout vascular plants except for ferns, peptide-mediated root-to-shoot-to-root long-distance signaling is likely to be a general strategy employed by all higher plants for environmental adaptation.
It seems odd to claim that plants “have evolved sophisticated responses‘, given that the peptides they studied “are conserved” (i.e., unevolved) throughout the plant kingdom. The researchers never got around to explaining how this evolution happened. Would a blind, unguided process produce a “sophisticated” anything, especially one that is functionally effective and information-rich?
We’ve been reporting on this phenomenon since 2001 (see links in 4/26/07 entry). Isn’t this great? It’s exciting to think that your potted plant has its own intranet and email system! Tell your office friends about it at the water cooler if there is a potted plant nearby. Tell your kids about it on the nature trail.
The evolution-talk is so useless (see 10/19/14). Secular scientists have a bad habit of claiming that things “have evolved,” no matter how complex the system under consideration. It’s even worse when they say that plants “have evolved… to” do something. That’s nonsense in Darwinian theory; nothing “evolves to” reach a goal. Darwinism is a restatement of the Stuff Happens Law. Nothing happens “for the purpose of” anything else. Darwin was supposed to rid biology of teleology, remember?
Look: the system is composed of multiple interacting parts (irreducibly complex), and it involves signaling for a function (complex specified information). These are the hallmarks of intelligent design. Both parties, root and shoot, have to know the language and the protocol; they use a language convention. What if the root sent a message to the shoot, and the shoot responded with gobbledygook? The entire system has to work, or else nothing works. Every case of a language convention used for signal and response in which we know the origin of the system is the result of intelligent causes.
Having dismissed the illogic of evolutionary theory, can we now step back and enjoy the wonder of what science has discovered about plants? They have an intranet! They use email! The proper response should be joy, wisdom, and worship for the Creator who told us that He made these marvels on the third day of creation (Genesis 1:11-13). Doesn’t it make sense that the God who communicates within Himself in the persons of the Trinity and with His creation would design beings capable of communication? It makes perfect sense. Science should have been looking for this. The Bible presaged it by stating, “In the beginning was the Word” (John 1:1). The Word is a Person who communicates, giving light to every man.
Incidentally, William Dembski has a new book out this month, Being as Communion, in which he makes a rigorous case for including “information” as the fundamental entity in the universe (see his video clips on the website). It should be an interesting read. After The Design Inference and No Free Lunch, it’s his third major treatise making the philosophical case for intelligent design (see Evolution News & Views). As a mathematician and philosopher, Dembski brings exceptional scholarship to the design debate. His strength is in making the case for ID robust against all possible criticisms from evolutionists and secular materialists. As important as the bare-bones case for ID is philosophically and academically, it cannot heal the soul. The late creation scientist A. E. Wilder-Smith (also a scholar with three earned PhD’s) also taught that information is a fundamental entity in the universe, but as a joyful, devout Christian, he used his scholarly logic to preach the gospel. If ID doesn’t get you to the God who made you, it leaves you incomplete, unfulfilled, and lost in a silent universe. Communicate with your Creator today. He sent you the message; now it’s your turn to respond.