Update on Plant Communication
Plants have both an intranet and an extranet. Some recent papers investigated further about how plants, though rooted in the ground, keep in touch with the inside and outside economy.
- Intranet: In 2001 (07/13/2001), and periodically since (10/04/2004, 11/09/2004) we reported the current thinking about how a plant knows when to flower, and described a kind of email system the plant uses to keep in touch with itself. Scientists have been hot on the trail of the mysterious “florigen” (whatever it is) that travels through the vessels to the growing tip and turns on the flowering process. They have known since 1865 that something travels from a sunlit leaf to the apical meristem where flowers are produced. Now, according to both Science April 20 and Nature April 26, they think the packet is not the messenger RNA from the FT gene, as previously announced (08/12/2005), but the protein it encodes. Understanding what the protein does upon receipt is an obvious next step. Then, what in a leaf triggers the email to be sent? And is the packet sent throughout the entire plant? For now, the botanist hackers are just trying to get good at sniffing the internet to find the packets, let alone decode the payload.
Down below, at the root level, what happens? A European team reporting in Current Biology thinks they have unmasked the signals that turn on (or off) root cell differentiation: “Analysis of the root meristems of cytokinin mutants, spatial cytokinin depletion, and exogenous cytokinin application indicates that cytokinins act in a restricted region of the root meristem, where they antagonize a non-cell-autonomous cell-division signal, and we provide evidence that this signal is auxin.”
- Extranet; When plants need to talk to their neighbors through their own kind of VPN (virtual plant network, our joke), they waft volatile compounds into the air. Some of these compounds are chiral – they come in left- and right-handed forms. Scientists are just at the leading edge of understanding what these compounds are and what they do. A news item in Nature described the work of a team that flew a Lear Jet over the forest canopy to gather some of the compounds. “A sophisticated survey of certain volatile organic compounds in the air over forest ecosystems shows how such work can reveal varied emission patterns of different chiral, or mirror-image, forms of these compounds.” Plants emit more volatiles than animals by orders of magnitude, the article states. Some compounds can repel insect pests, while others can attract pollinators. This article described how the plant can send out different chiral forms of the same molecule for different purposes. Some, for instance, appear to be temperature dependent, while others are light dependent. “Volatile organic compounds have a fundamental role in the coexistence of the flora and fauna in ecosystems,” the article explains, “But there is still much to learn about the relationships and interactions between species that can be related to an effect of naturally produced compounds such as monoterpenes.” The compounds may vary by species, by individual plant, and even by tissues within the plant. The scientists are comparing forest emissions from South America, Suriname and Finland.
The trees may not talk like the Ents in Lord of the Rings, but they do have a language that humans are just beginning to translate.
Don’t talk to your plants unless you learn the language. Suggested learning tool: a Lear Jet.